Been a while - new project, T04 Gas Turbine.

Moderator: Mike Everman

Post Reply
longjohn
Posts: 23
Joined: Tue Apr 11, 2006 10:51 am
Antipspambot question: 0
Location: Ipswich

Post by longjohn » Tue Jan 22, 2008 8:43 pm

I love this project, I am using it to guide me for biulding my jet engine based around this design, but reverse flow to allow me to biuld a better slightly larger combustion chamber, and also so I dont have to lengthen the turbine shaft.
Ash, have you stumbled across on the net my jet scooter creation? Its an external combustion chamber design using the whole turbo charger, a TO4E. I also wired in a second pump and put on a bit more tube on the exhuast with cone and fuel evaporator, as an afterburner.

When I first tried to ride it, I discovered how important it was to forget about standing up, and put on a seat and foot pegs!! It just gets the speed wobles when you stand up.

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Sat Aug 16, 2008 11:29 am

OK Guys, back to the T04GT! :)

I have decided to ressurect the T04GT engine for sake of testing out a few mods prior to committing to specific designs within the TV94 TurboFan build. I pointed out that the profile of the turbine inducer tips are cupped and believe this is done to better suit the gasflow vectors involved in a turbocharger turbine housing. Due to the geometry of the NGV in this engine, the gases are all coming in perpendicular to the turbine inducer and I want to experiment with the effects of mocking the OE turbine housing gasflow as best as possible to see what effects it may have. The T04GT engine project has served as an invaluable asset to my knowledge of gas turbines but it was never fully "finished" to eliminate all its quirks. Well, the time is now and I'm excited to once again move forward in the development of this tiny powerplant..... LOL, So, without further adeu, welcome to "The Ressurection!" :D

I have chucked the turbine into the lathe and bored a larger seat at the turbine exducer for the live center. The OE center is surprisingly shallow and only had a taper face of around 0.030" or so. I opened that face out to around 0.100" with a proper taper to suit the live center in my tailstock.

The turbine shaft was centered up within a few ten-thousandths in the chuck and the tailstock w/live center was mated up. I had some reservations in trying to machine the turbine shaft as my previous dealings in trying to machine them resulted in an incredibly rough cut with a surface finish that would tear flesh off like a lion's tongue.

I'm not sure if it is due to heat cycling or simply that I have gotten better at setting up the lathe and bit, but I was able to machine the shaft with very little trouble. I turned down the shaft to a diameter suitable for a LH M6X1.00 thread while leaving a ~10mm long shoulder from the shaft boss for centering. The threads take up around 75% of the length at the quill and the tip was machined down to an o.d. fitting the thread base diameter.

I have the new shaft mounted into the lathe and ready for machining. I have faced off one end and bored a center into it and the entire shaft has been faced off to clean it up as well as reference concentricity at the end with the centering bore. I will use my ball-bearing shaft support assembly to hold the far end of the shaft (end away from the chuck) and get the boring and threading done to allow insertion of the turbine.

The idea here is to semi-permanently mount the turbine into the shaft extension and use a larger diameter rear bearing to ride the full diameter of the shaft. The previous layout used a 10mm i.d. bearing fitted to the turbine shaft and then the extension was screwed on - clamping the bearing between the shaft boss and the end face of the extension. This arrangement just proved to be more problematic than I would prefer to see in a component rotating into the 6-figures per minute. It seemed like every time I reassembled the engine I would have to re-balance the bits again.

With this new setup I wont have to dismount the extension from the turbine. The whole shaft will simply slide out the back of the engine once the compressor and turbine exducer flange are removed. A small shoulder will be left in the extension back near the turbine in order to prevent the rear bearing from sliding all the way to the back of the bearing tube and a preload spring will be fitted against the inner face of the outer race of the rear bearing. All axial movement will be constrained via the front bearing. The rear bearing will also be placed a small distance forward from where it has previously been located so as to reduce it's exposure to heat.

A new bearing tube will need to be machined and I will be going with a sealed bearing tube arrangement. The OE turbine shaft seal will be used as well as a collar installed behind the compressor wheel to handle another shaft seal at the front end. The lube and cooling air for the rear bearing will be accomplished similar to how the evaporators are designed. A 1/8" tube will run down the length of the bearing tube and provide cooling air for the rear bearing. An additional hypo tube will be installed into the fuel ring and will insert into the head of this tube. The center of the bearing tube will be fitted with a 1/8" dia SS tube which will run out through the diffuser assembly and dump into the fuel tank. A small needle valve will be installed between the engine and fuel tank to allow adjustment of the bypass volume.

My main concern with this is metering the fuel into the bearings - too much and the balls will basically hydroplane in the races which will create excessive skidding of the balls - they wont stand up to much of that I'm sure. However, the return line to the tank will use a piece of clear tube which should at least give some indication of the volume of lubrication going through the bearings. If that proves to be too difficult to determine visually due to the bypass air velocity, I can run some tests by dumping that bypass into a metered container and make adjustments as necessary.

The shaft extension and bearing lube/cooling will be my first point to address and test. It sounds pretty straight-forward to make these mods, but this darn T04 engine is so small that I almost feel like I'm working on a wristwatch, LOL....

Here is the finished turbine shaft:

Image

This shaft setup is similar to how Garrett machines the shafts for their boreless compressor wheels - this is a "take" from their works. Without having the bearing "sandwiched" between the turbine shaft head and extension shaft face, rather, the extension shaft end face directly seating to the turbine shaft boss, a much better interface is created. Once the extension is bored for the turbine to mate up, the turbine/shaft will be mounted between centers and machined to precise dimensions for fitting 15mm i.d. rear bearing and 10mm i.d. front bearing, as well as the quill machining to fit the compressor and locking nut. I wont use any sort of shaft locking to hold these two together other than torquing the shaft down to around 6-7ft/lbs for a nice solid mating. The compressor nut is always removed by holding the compressor wheel in one hand with a rag wrapped around the blade tips and a pair of channel locks to remove the nut.

This should finally address the small imbalance issues I faced with this engine and just being able to maintain good balance will take a decent load off the bearings. Combining that with a better lube/cooling system should provide the kind of longevity I would expect from a commercial engine. Even further, without dumping lube(fuel) and air into the turbine section that I believe is actually burning on its way out, I should even see a performance benefit by being able to run a little higher fuel flow without reaching the thermal limits of the turbine.

Once the shafting and bearing tube is addressed, I'll get to work on the 4th (and hopefully "final") NGV. The NGV backplate will have a profile that creates a gasflow vector actually moving towards the front of the engine to try and mimic the flow characteristics of the OE turbine housing for this wheel. This may prove a bit tricky to pull off as in order to create this duct geometry will require a larger flow area through the 90-degree radius between the CC outlet and turbine inlet. I think the only way to pull this off will be to cut the outer CC liner about half-way back and attach a slightl divergent cone to mate up with a larger o.d. NGV backplate. I just can't see funneling the CC gasflow down at its exit to then expand it and re-funnel it through the radial section of the NGV. I think I can pull it off with some degree of elegance and use brute-force if necessary. :lol:

I'll drop back in once the shaft extension is complete and post up some pics to show the goods. :)

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Mon Aug 18, 2008 10:21 am

Just about finished up with the new turbine shaft extension. :) I made a small change to the original plan by way of cutting the base shoulder of the turbine shaft with a 1.5 degree angle. This is the largest diameter section of the turbine shaft just forward of the main shaft face. This taper will ensure that the turbine remains seated into the extension. This process took quite a bit of time to get the proper diameter inside the extension so that the taper would just begin to bind as the extension's face mated with the turbine shaft face. There is about 10 ft'lbs of torque that was applied to sinch these two up and I'm really happy with how it turned out.

Once the extension was installed, the whole assembly was mounted between centers - live center in the tail stock and a DIY center in the chuck with a lathe-dog arm fitting between two of the turbine blades to provide drive. The 5/8" diameter extension was turned down with about a thousandth of an inch extra for final sanding to get a nice fit with the bearings and compressor wheel.

I found that when turning a long skinny part like this, you want to draft cut all of your diameters and leave about 7 thousandths on them. Once you have brought them all down to this slightly-oversized diameter, then begin shaving off a little at a time. I found that once I cut the front bearing section and followed with the compressor section, there was a slight bit of runout in the front bearing shoulder. It was less than a thousandth, but enough to be of concern. Fortunately I just happened to turn the shaft down in this process so there was material available to do the final light passes to true everything up. I would imagine that what I discovered is likely taught in books or classes but I haven't taken any machining classes or read any books about it - just kindof learning as I go along, LOL.

The back end of the extension, about 1/2" from the interface between the extension face and turbine shaft face, I left a small shoulder to provide a stop for the rear bearing.

I'm really hoping that I have finally solved the issue with maintaining balance in this piece. This bit of the engine and the bearing failures I was having previously just got to be too much and with the increase in business volume it was actually a relief to step away from this engine. I almost feel foolish to have spent all this time and effort on this piece again when the TV94 engine design will not be using this extension specifically for the fact it was so problematic. But, I built this engine as a testbed for much bigger plans and it is good to see that its real purpose is bringing it back to life once again. :)

Using the shaft seals will require a close running tolerance between the shaft seal holders and both the NGV and diffuser plate. I will likely be installing bronze seats into the diffuser and NGV section so that if a bearing does fail, these seal holders will provide radial control of the rotating assembly and hopefully prevent damage to the shaft and comp/turbine. I just hope all of this works out as if it doesn't I think I'll stain and varnish a nice piece of oak and bolt the engine to it to make an interesting paperweight. :)

Here is the pic of the turbine with extension - still needs the LH threads cut into the comp quill and the bearing and comp surfaces final sanded down for a nice fit, but I am happy with how it turned out and look forward to seeing this engine run at least once more! *Fingers Crossed!* :D

Image

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Tue Aug 26, 2008 3:49 pm

Been pretty busy as of late with the GT stuffs. :) After I got the new shaft extension finished for the T04GT I pulled out an old P-trim turbine I originally had for this project that got scrubbed when I tried to machine the shaft with carbide tools - the hardened shaft steel just wasn't inclined to let me cut it and it was scrapped. Well, I wanted to see about doing something with it so I built a toolpost grinder for my lathe.

Stature electric 1/4HP 5400RPM 12V DC motor. I machined a shaft extension for it as well to hold the grinding wheel and welded an old vice plate to the motor's casing for mounting to the crossslide. I then drilled and tapped two M8X1.25 holes into the side of the crossslide and mounted her up. I have been using my Dewalt's drill battery to run the grinder motor and it works very well and provides plenty of runtime.

Image

Image

Then I proceeded to grind the shaft identically to how I modified the other turbine and then made up another shaft extension for it. It turned out beautifully. :) So, why have only one rotating group when you can have a spare too? :) (BTW, I machined the shaft extension for the second group to fit a 13mm i.d. rear bearing vs. the 15mm used on the other shaft. I'm going to fit this "ressurected" rotating group into the engine first and see how it fares with a 13mm dia shaft - I haven't calculated what the CRS is on this group as determining mass distribution across the radial turbine is rather difficult, but if this shafting blows up (LOL), I have an extra. :lol:

I have found that the grinding wheel needs to be absolutely true and balanced when grinding. Any small imbalance or runout in the grinding face produces a really poor finish on the shaft. Even with really good balance and the wheel properly dressed, the finish on the shaft surface still shows some degree of feathering. But, just touching off on the shaft with some 600-grit paper removes these small artifacts. I think this feathering effect can be pretty much eliminated though - I only dressed the wheel by hand with a diamond wheel and after doing some grinding, it does appear that the wheel isn't perfectly dressed as I can see (and you can see in one of the pics above) equally spaced areas where some of the shaft metal has deposited. I need to get a real diamond facing tool and mount it into the lathe chuck to dress the grinding wheel (not driving the lathe chuck, just using it to hold the dressing tool while the grinder is spun up and using the crossslide to move the grinder).

This electric motor has a spring washer in the rear bearing seat to provide bearing preload but I think it may also help to go with a slightly stiffer spring washer to load the bearings more to prevent radial slop - I just dont see the current spring washer providing enough preload on the bearings to control the kind of mass I have attached to this motor. I could even go with some ceramic bearings to smooth things up even more if I still see feathering once the wheel has been properly dressed.

I will also be able to "clip" the turbines very accurately with the grinding toolpost rather than the Spartan approach of grinding the exducer with a sanding wheel in the Makita while it turns on the lathe, LOL.

Image

I also repaired the old 60-1 compressor that was damaged when the compressor diffuser bolts backed out and scrubbed the back of the comp wheel and bent the tips of the blades a little. Machined a quill in the lathe to mount the wheel and then trimmed the back of the wheel where the bolts hit it and then straightened out all of the blade tips. So now I have two rotating groups - thanks to the toolpost grinder.

Since I had been having issues with balance before, I wanted to go about the balancing in a bit more refined approach, so, I started in on building a balancing rig. I was originally going to make the actual "sensing" component completely mechanical with a set of adjustable points on the rear carrier plate's swingarm, but just from playing around with it a little bit I can see that the amount of actual motion of the swingarm is so terribly small that I dont think it will offer the kind of sensitivity this will need. I have sourced a piezoelectric buzzer to be used as a sensing element and will build the trigger circuit and install a drive motor to have a functional rig. I will also get an aluminum case/base for the balancer which can house the electronics and mount the rig atop the casing.

I have never played around with piezoelectric materials before and it wasn't until last night after doing some research have come to find just how amazing this material is. OH the things this little piece of info will do for me through the course of time! :) I am also going to get my hands on some simple piezoelectric sensing elements and an accelerometer sensor to play around with. Lots of really good projects and tools have come from the 'ol T04GT build and in revisiting this project, it appears they just keep coming. So, I'm looking forward to playing around with this material and finishing the balancer. :)

It is all built from 1/4" aluminum plate, some steel shaft, a bronze bushing, and teflon sheet for the journal supports. The horizontal swingarm at the rear has two flanged ballbearings at the fulcrum and the piezo sensor will be placed below the "Y" journal between the swingarm and baseplate to measure the mass imbalance as the assembly rotates and trigger an LED for a stroboscopic effect when the heavy side swings low. Marking one of the blades will allow me to see where the heavy side is and go from there. The front journal support is adjustable both in height as well as axial position to allow me to mount shafts of differing lengths as well as be able to level shafts which have differing bearing journal diameters, such as seen with the two recent shaft assemblies for teh T04GT. The teflon sheet was rolled around the top of the "Y" supports and riveted through with a backing washer. Rolling the teflon sheet around the top like this produced a very narrow point of contact between the shaft and the teflon itself to reduce friction. This will also allow for some degree of mis-centering of the front and rear "Y" journal, which is possible to some small extent (maybe +/- 0.030") by way of the slotted front journal bracket. Just adding a drop of some light machine oil to both journal surfaces allows the group to rotate very freely and just spinning it by hand, it will continue to spin for many seconds on its own.

Image

Image

The swingarm is fixed using two 8mm o.d. X 3mm i.d. flanged bearings I dug out from my old RC helicopter parts bin. Two holding plates were machined and bolted to the rear support bracket and then the gap between them was end-milled for a low-tolerance fit of the swingarm with the flanged bearings. I used an M6X1.00 SS allen head screw to fix the swingarm - I mounted this screw into the lathe and turned down the end of it to 3mm for a snug fit into the i.d. of the bearings and left 1/4" of the threads intact just behind the bolt head. The baseplate was mounted in the vice on the mill and a 3mm lead hole was bored through both plates, followed by a 3/16" bore through just one plate. This 3/16" bore was tapped for the M6X1.00 threads. When the fixing bolt is installed, its 3mm dia locates the bearings and then fits snugly into the 3mm bore in the holding plate on the far end. Then the bolt is simply screwed into place to lock it down without having to worry about clamping the bearings and producing friction. At the opposing end of the swingarm, there is only about 0.035" of "play". I will machine a set of guide plates with a piece of teflon sheet attached to their faces for controlling the end of the swingarm and eliminate this last bit of play - the teflon sheet will provide a very smooth and low-friction interface for guiding the swingarm. Right now the swingarm extends 2" beyond the center as I was going to put the contact points out far to get a mechanical "amplifying" effect on the swingarm motion. I will be cutting the last 1" or so of that off as well as the arm on the baseplate that extends out below it. No need for that at this point. The centering shaft was machined down to around 0.375" o.d. with a 0.550 flange where it meets the front face of the rear support bracket. The shaft just behind the flange was machined to 0.375" dia, 1/4" long, and then the last 3/8" of the shaft was turned down for threading to an M8X1.25 pitch. The rear support bracket was bored to 0.375" and the shaft mounted with a washer and a self-locking nut.

The shaft bushing in the base of the front support bracket was machined with a 0.500" o.d. and a 3/16" flange was cut at one end. I left about 1/8" length of the o.d. just behind the flange with some extra material - about 0.505" to allow for a press-fit into the bracket. The i.d. was bored to fit snugly over the alignment shaft with about a thousandth of clearance and a lube galley was cut at axial length center for some grease to be smeared into. The front support bracket was bored to 0.500" and the bushing was pressed into place. There is no locking of the front support bracket to the shaft itself - when I machined the hole in the rear support bracket I cut it a few thousandths lower than its vertical position in the front bracket so the shaft is actually producing a bit of a clamping load on the front bushing to hold it securely flush to the baseplate. The front bracket slides along the shaft smoothyl but with adequate resistance due to this machining - should work out pretty well.

The piezo likely will not survive having to support the mass of the turbine by itself so I will machine an adjustable seat in the baseplate for a spring to be installed. I really am under the impression that the piezo buzzer will prove to be too delicate and will get damaged easily - the piezo vibration sensors sold through DigiKey are simple flexible "sheets" of which I may end up building a small holding plate to fix one of these to and have the end of it placed either atop or under the swingarm so the piezo sheet will flex and produce its output signal. This would also prevent the piezo element from being damaged, say, if one were to accidentally drop or hit the swingarm (or anything attached to it) and cause a hard impact on the piezo buzzer disc. I'll just have to play around with these different piezo parts to find the best solution. Here's a pic of the piezo element on DigiKey: (this piece is small - 0.520" X 0.980")

Image
DigiKey Web Page: http://search.digikey.com/scripts/DkSea ... MSP1006-ND
Datasheet: http://media.digikey.com/pdf/Data%20She ... Sensor.pdf

If you dont have knowledge of piezo technology, you really gotta take a few moments to read up on it - pretty fascinating stuff and it will set your little creative genius off. :) Here's a good page I found on Wiki:
http://en.wikipedia.org/wiki/Piezoelectric_sensor

I have a small electric motor (1.25" dia) that was used in one of my old electric RC helis which I plan to use as the drive motor. I'll machine a pulley for it and use an oring to drive the rotating assembly. The electronics for this unit will also have a motor speed controller based on the same SG3525 PWM IC used to provide fuel pump control where I can set the base frequency into the high KHz range to avoid it from affecting the piezo sensor. That IC uses a simple analog voltage input for PWM control so a simple 2K knob with a couple of resistors can be used to control the input/control voltage for the IC. The trigger circuit will be built using an LTC1050 chopper amplifier setup as a comparator - in fact, I actually plan to use the optical tachometer circuit as it is already built and proved to be too finicky on the T04GT. The circuit is powered by 5V and its non-inverting input is conected to a 10K POT with two 470 ohm resistors connected to ground and +5V. This pot sets the trigger level which is compared to the input from the piezo sensor. When the piezo sensor's input exceeds the trigger level, the IC produces a HIGH signal on its output line. This output line will be connected to the LED illuminating the rotor head. I could go more complicated and build a circuit that pulses the LED for a fixed duration any time the chopper amp's output goes high, but I think leaving it the way I propose will actually provide myself some feedback during the balance process. Ideally you want the LED to pulse for a very short period of time to create a strobe effect otherwise you are just going to see a blur. So, with the simple circuit, if the rotor head appears blurred, I know I will need to turn up the trigger level. As the trigger level is increased, the "blur" effect will reduce as the LED's pulsewidth decreases. So, this "simple" circuit should actually provide for a more user-friendly experience than a more complex circuit design......... well, that is only if it even works at all! LOL :lol:

Here is a pic of that circuit again: (which will be eloquently hidden within the base/case)

Image

The on-board POT will be removed and a face mounted knob will be installed into the base/case along with a second knob to adjust the motor speed. A small power supply will be built into the case to provide conditioned 5V and 12V for the circuits and I'll attach a pair of alligator clips for connecting the rig to my shop battery (just an automotive battery I use for various things such as this).

I am going to spend my spare time getting the balancer built and fine tuned before rebuilding the T04GT. I still need to machine a new bearing tube and make a new NGV so it will be a bit of time before I get to hear her sing her song again but she will very likely run better than she ever has before - at least, she has a much better chance this time around so long as the new bearing lube/cooling arrangement works out. At this point I am dedicated to fully ressurecting the T04GT and getting her to a point where I can enjoy some decent service life rather than a few good scooter runs followed by weeks of rebuilding. So, time to live up to the tag and get back to pimpin'. :)

Image

More to come soon - I can only hope this long post was worth the time to read, LOL! :wink:


More to come soon! :)

Mike Everman
Posts: 4928
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Mike Everman » Thu Aug 28, 2008 11:00 pm

As always, Ash, great read, and fantastic build notes for tools. You are having SOME FUN.
As to the toolpost grinder, I'd move the wave washer so the rear bearing is the moving race and the wheel end is the hard stopped one. Most motors are not made that way, unfortunately. I'd also shoot for the lowest RPM you can get on the lathe chuck, which you probably know, but it'll get you the best finish.
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Mon Sep 01, 2008 2:29 am

Thanks for the feedback, Mike!

I have more progress to report on the balancing rig - she is finished! :)

I was going to use the circuit I built for the optical tachometer but decided to leave that circuit alone and build a new one. I took a trip up to Radio Shack to pickup a few odds and ends and went through the component cases and actually found everything I needed to build the balancer - sweet score at the Rat Shack! So I picked up several piezo buzzers, an LM339 Quad Comparator IC, a few 10K panel mount POTs, some nice machined aluminum knobs, a few switches, a fuse holder, a fan, a few TIP120 darlongton transistors, and well, I picked up about $350 worth of stuff which also included a few packs of rechargeable batteries, a soldering station, and other misc items I use around here.

I put together the comparator circuit and linked in the piezo buzzer element to test its operation - was pretty interesting to see that even with just minimal tapping of the piezo, it would generate ~8V potential. I suspect that this transducer will work out very well in this application given that the LM339 is capable of seeing about a 2mV difference between inputs - I can only imagine what small amount of mass would be necessary to produce a 2mV output on the peizo. For kicks I blew a few pulses of air from my mouth onto the piezo and it would trigger the output on the comparator. :)

I took apart the extra timing light I had here to get the guts out and also picked up a different xenon bulb, one of the u-bend style as the timing light had a long straight tube that would have required a larger diameter mounting tube.

An aluminum plate was machined to hold the piezo element directly below the shaft center on the swingarm and I used 3M double-sided viscoelastic adhesive foam to mount the piezo, electrically isolated. In the bottom of the swingarm I drilled and tapped a hole for a small screw to act as the pin for transfering the load to the piezo. I left one of the small springs in place to provide support for the turbine/shaft so the piezo wouldn't have to bear the full force of the rotating part. At the other end of the swingarm I installed a small screw that can be tightened down to contact the rear baseplate and prevent the piezo from being damaged when installing/removing shafts and for storage. This screw backs the swingarm from the piezo and leaves about a 0.060" gap between the screw and piezo plate.

I also received the extruded aluminum case to put the guts into and got everything mounted up - using standoffs for teh electronic bits inside. I cut out an endplate for the housing and left a tab for mouting the strobe light housing. I turned down a piece of aluminum tube I had here so that I could install the lens that was on the timing light and cutout a backplate and installed a grommet for the wiring. A piece of teflon was used inside the case to electrically insulate it from the ~600V that the strobe receives from the strobe circuit.

I mounted up a shaft and started playing around with balancing one of the T04GT turbine/shafts. I have spent about an hour with it, adding some aluminum tape to the heavy side in intervals. There is a process to using this rig:

Start with low rotational speed and with the sensitivity set to the lowest setting. Increase the sensitivity until the strobe fires. The heavy side will be the lowest point.
Leave the rotational speed and sensitivity adjustments alone, turn off the balancer. Remove material on the heavy side. Reinstall the group and turn the balancer back on.

I have found that in running the shaft at the same speed, each time material is removed, the sensitivity has to be turned up a little more. I kept going like this until I was at the max sensitivity and then I increased the rotation speed a step at a time and left the sensitivity alone. I would just raise the rotation speed each time until the strobe began firing.

The way the electronics work is pretty simple. The comparator has two inputs, one is connected to the piezo and the other is connected to the adjustment knob. The adjustment knob allows you to set the voltage threshold that must be exceeded by the piezo at which the comparator will turn its output on. The output is connected to the strobe circuit. When the heavy side of the turbine/shaft is bottom dead center, the piezo will be at its maximum voltage output. The sensitivity adjustment allows the threshold to be adjusted to just a few millivolts below the peak output voltage of the piezo. It is interesting to see the response of the setup when you lower the threshold voltage - it will actually appear as though the heavy side is moving. The trick is to turn the sensitivity up just enough to where the strobe doesnt fire at all and then back it down just a hair until the strobe begins firing again. AT this point the sensitivity is set dead on and the strobe will be firing just when the heavy side is low.

Im going to continue playing with it and I Will build a calibration tool to double check the accuracy of the machine. I will turn a shaft and intentionally install a small straight piece of wire sticking out of the side of the shaft. I will be able to spin this up and see in closer detail how accurate the machine is. :) I will also be able to do this with a known amount of mass to determine empirically just what kind of precision I can balance down to.

So, enough with the chitty chat, here's the pics!

Image

Image

Image

Image

Image

Image

Image

These last two shots were taken without the camera flash and with the balancer running. You can clearly see the stroboscopic effect here even without motion video! :)

Image

Image

So now Im going to get these two turbines/shafts balanced up and then make an additional shaft for balancing the compressor wheels. Unfortunately although this process is considered dynamic balancing, it isn't truly a fully dynamic balancing rig as I would need to have two piezo sensors on both journals and spin the assembly with everything connected. I have plenty of the extruded casing left over and the comparator circuit actually has four comparators (I'm only using one), so perhaps sometime down the road I could make the balancer v.2 with twin piezo, twin strobe, etc etc.. But for now I think this will work out sufficiently. I'll just have to get the T04GT back together and see if I Really am getting good balance! :lol:

I'm pretty happy with how this balancer project has turned out so far - it has come together relatively easily, although there were a few hiccups here and there, but I dont give up very easily and I've been prett determined to do this and there isn't much going to stop me when I have my mind set on something. :)

I'll report back once I have balanced one of the wheels and also tried spinning up a known off-weighted shaft for calibration.

Mike Everman
Posts: 4928
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Mike Everman » Mon Sep 01, 2008 3:40 am

I'll say you don't give up easily. You are an amazing guy, Ash. One of these days I'm going to offer you a job that I'm sure you'll decline, but I'll do it anyway! ha
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Mon Sep 01, 2008 9:25 am

Hi Mike,

It is rather interesting that my father, as of the past few years, has been dropping "hints", if you will, for me to "get involved in robotics". The other day, while mulling away on the lathe, it occurred to me that what he is suggesting is exactly what I am doing, LOL! I think a lot of people, when the word "robotics" comes up, think of eletro-mechanical contraptions like the no-name robot in "Lost In Space", or "Rosie" from "The Jetsons", or perhaps even as sophisticated as "Data" from "Star Trek - The Next Generation". What intrigued me the most about this was the simple fact that it appears most people over-generalize this particular category and utterly lose touch with the finer defining aspects of what "robotics" is all about - shocking to me because I felt that my father would have identified this long ago, LOL. When it comes down to it, I am already "in" robotics! :) By definition, "Robot" or "Robotic", does fundamentally require that the machine possess some human-like structure. However, my dad never said "robotic", he added that "s", which makes all the world of difference, LOL. By definition, "roboticS" classifies any electronically controlled mechanical device. :)

I know this may sound like splitting hairs, trivia ad nauseum, or perhaps some mediocre exercise of semantics. But on the same token, for those who have actually built a "jet engine" in whatever shape or form, in the time(s) you have carried conversation with someone about you "building a jet engine", you can clearly relate to exactly what it is I am getting at here (in the flip-side, "other side" of the token). :) They look at you as if you're talking about building some Gemini or Apollo powerplant, LOL! They aren't ROCKET engines! ROFL!

Fortunately for those of us who have an affinity towards gas turbines, there is a common forum of which to exchange our ideas and our experiences (And you should gravitate yourself to offering up even just a small donation to the site from the home page to support Mike's hard work to keep this forum). (BTW, Mike, you might want to check the code for that donation link, it isnt' working for me and you're making me put my foot in my mouth here! ROFL!) Everyone else "out there" probably thinks we are building engines that will take a man to the moon and will likely blow ourselves up in the process, ROFL!!! :lol:

For what it is worth, Mike, I would be honored to receive an offer to work with you. From what I saw of the items you brought by the house during your visit, I could easily see myself diving head-long into it. :) The only issue I see that would likely become a "deal-breaker" is the fact that I thrive on autonomy and diversity. The business I own consists of the abilities of one, fed from the variety and opportunity to do as I please. The sales, word-of-mouth, the income, all reciprocate the opportunity to do a wide variety of "things" I can choose from. Some of those efforts have proven uneconomical to pursue and others have succeeded by leaps and bounds. In short, and simply by experience, I must state that I work much better alone and humbly decline the offer in advance. It is more "my problem" than anything else and I'm not hesitant to admit it. We are the way we are and it is what it is, right? :)

The way I see it, money is just a means. It is not the end goal. The money simply affords opportunities, but at the same time, the money is not a necessary element for opportunity. We, as intellectual human beings, are afforded invaluable opportunity by the possession of mind. "Getting Rich", the concept of such, completely lacks context. Life is like the flow of water through a pipe. Sometimes the pipe will widen and slow the water, sometimes it will tighten and speed up the water, sometimes it will come to a junction and split the water. Through the process, you are just one particle of water in that stream, trying to do what you want to do and having to work with all the elements at play to achieve your goals. In perfect context, "getting rich" is simply a "pipe dream".

So long as my efforts continue to afford me the opportunity of pursuing the goals of which I lay out to achieve, then I am making all the money I need to make. While there is room to question the validity in my abject (LOL) philosophical post here, I'll end with a perfect quote from Baz Luhrman, "Sometimes you are ahead, sometimes you are behind - but in the end, you are only in a race against yourself." and just leave it at that for you to contemplate. :)

Mike Everman
Posts: 4928
Joined: Fri Oct 31, 2003 7:25 am
Antipspambot question: 0
Location: santa barbara, CA
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Mike Everman » Mon Sep 01, 2008 3:28 pm

The way I see it, money is just a means. It is not the end goal. The money simply affords opportunities, but at the same time, the money is not a necessary element for opportunity. We, as intellectual human beings, are afforded invaluable opportunity by the possession of mind. "Getting Rich", the concept of such, completely lacks context. Life is like the flow of water through a pipe. Sometimes the pipe will widen and slow the water, sometimes it will tighten and speed up the water, sometimes it will come to a junction and split the water. Through the process, you are just one particle of water in that stream, trying to do what you want to do and having to work with all the elements at play to achieve your goals. In perfect context, "getting rich" is simply a "pipe dream".
Ha ha, Ash, no need to quote anyone else. That was it in a nutshell. I just read it aloud to my wife.

My great late mentor and partner, Max Benton, taught me by example how to harness an entrepreneurial spirit, which I was, too. I actually could have stayed and invented for him indefinitely if the corporate direction had embraced the robotic aspect of the spacecraft mechanisms we were doing (to not just deploy the thing, but to be responsible for pointing it as well). The company did eventually, but still not yet to the level I wanted to take it.
He often said to me "I only expect ONE good idea from you a year." Otherwise, he let me play, and opened the door just long enough to feed in software and materials and support. What I have learned is that there is honor in serving the right master, if one is given the resources not easily had, the credit where it is due, and ownership enough that one's entrepreneurial spirit is satisfied.
While I'm still not finished exploring commercial robotics, the time will come that my need to build something that flies in an altogether different way will alter the course of my company, or drive the need to let that one go and create one that will be dedicated to this.

Let's revisit this some other time, as it is not yet the time, and I don't want to dilute this wonderful thread any more than I have!
Mike
__________________________
Follow my technical science blog at: http://mikeeverman.com/
Get alerts for the above on twitter at: http://twitter.com/mikeeverman

fastnova
Posts: 55
Joined: Sat Sep 06, 2008 8:14 pm
Antipspambot question: 0
Location: Sussex

Re: Been a while - new project, T04 Gas Turbine.

Post by fastnova » Fri Sep 12, 2008 10:42 pm

It’s a shame you don’t live near me, I would have stuck that shaft on our centre-less grinder for ya and had it done in seconds. Seems like such hard work for something so simple. Shame the carbide tools didn’t work, you do need to spend series money on tips if you want quality, has anyone ever tried to machine duplex with cheep carbide, good luck to you!
Same with hard machining, the results can be very impressive but you need the tooling.
We might have some old ones floating around at work if you want them; we used to do loads of hard machining, but not any more so are kinda superfluous.

Wow, using words like that makes my head hurt.

Ps.
I like your work, took me fricking ages to read the whole topic. I am looking to do something similar but on a much smaller scale.
I don’t see problems, only opportunities.

Ash Powers
Posts: 176
Joined: Sat Sep 04, 2004 7:17 am
Antipspambot question: 0
Location: Edgewater, FL
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by Ash Powers » Sat Sep 13, 2008 5:29 pm

Hi Fastnova,

Thanks for the feedback! Building the toolpost grinder wasn't terribly difficult to do and I already had everything here to put it together- just took a little bit of time to sit down and think of how I could build it and then find the pieces here in the shop to make it happen. The results so far have been positive and I recently got ahold of a diamond dressing tool which has allowed me to get the stone perfectly round. I ground on a shaft the other day just to see the results with a properly dressed wheel and there is a 100% difference in finish now - it finishes the shaft with the same kind of surface you see on a valve face when it is ground in the same manner and no more feathering is seen on the shaft face. The one other thing I will be doing though is building a speed controller for the motor to put the finishing touch on the setup. The one thing I really like about the grinding technique is that it doesn't appear to place as much load on the shaft as cutting tools do. In machining the shaft extensions for this engine I have found that you need to be really careful about the last few thousandths for each of the bearing seats and compressor quill. You want to get all of the heavy cutting done for all of the surfaces before you do the final cuts to get it down to the exact size as the heavy cutting places loads on the shaft that actually bend it a little.

I dont forsee myself using the toolpost grinder all that much in the future though - the TV94 turbine shaft actually cut very well with carbide tools and wont require the use of the grinder. It seems that only the smaller turbocharger turbine/shafts have been hardened and I'm not sure how much work I will ever be doing with those.. I do have one project I will eventually be getting to where I will be grinding a pair of Garrett T28 class turbine shafts for fitment into ballbearing races in a garrett BB turbocharger cartridge but I dont have any intentions on getting into the turbo building business.

I'm relatively new to the whole machining field and am not all that well versed in the variety of processes or tooling - a lot of the time I've spent on the machine has been actually learning and devising the processes needed to fabricate the pieces I've made and all of it has been trial and error. I would love the opportunity to learn from someone as experienced as yourself when it comes to this kind of equipment! :)

Thanks again for the feedback - looking forward to seeing some of your work as well!

-Ash

fastnova
Posts: 55
Joined: Sat Sep 06, 2008 8:14 pm
Antipspambot question: 0
Location: Sussex

Re: Been a while - new project, T04 Gas Turbine.

Post by fastnova » Sat Sep 13, 2008 8:23 pm

I wouldn’t go as far as saying I am greatly experienced, I have only been in engineering since I left school 7 years ago. I have experience in most areas of engineering, especially manual machining. I find this gives me a good background to cnc, for example, I actually know why the tool cuts the metal rather than it just does and that’s it.
The company I work for is trying to employ a new setter operator. We have had a few guys in strait from university with engineering degrees and all sorts, they think they are the dogs danglers when in fact all they have is book knowledge which I useless. My boss was showing this one bloke round, he handed him a drill pointed him towards the off hand grinder and asked him to sharpen it, the guy just stood there with this “is that even possible” look on his face. I haven’t laughed like that in a long while. :lol:
Back to the point. Whatever you want to know just ask, if you got something you want to make but not sure how to go about it, just send me a pic, drawing or whatever and I will do what I can to help.
I may even be able to knock up a little part here or there if you haven’t got the means and post it to you.

I will be starting a kinda build log of my first project a bit later so if you have any advice or constructive criticism then please feel free, I may know a thing or two about cutting metal but other than how/why they work gas turbines are rather new to me.

Keep up the good work.
I don’t see problems, only opportunities.

fastnova
Posts: 55
Joined: Sat Sep 06, 2008 8:14 pm
Antipspambot question: 0
Location: Sussex

Re: Been a while - new project, T04 Gas Turbine.

Post by fastnova » Sat Sep 13, 2008 8:31 pm

Ash Powers wrote: The one other thing I will be doing though is building a speed controller for the motor to put the finishing touch on the setup.
Talking of speed controllers, I used to work in the toolroom for a company manufacturing potentiometers; I have loads of the dammed things some ware. Let me know what kind of resistance your after and I will see what I have.
I don’t see problems, only opportunities.

larry cottrill
Posts: 4140
Joined: Sun Oct 05, 2003 1:17 am
Antipspambot question: 0
Location: Mingo, Iowa USA
Contact:

Re: Been a while - new project, T04 Gas Turbine.

Post by larry cottrill » Mon Sep 15, 2008 11:53 am

Ash -

Man, I have to agree with the others (who were more prompt in their comments) -- the balancer is a beautifully wrought instrument! Your comments about the sensitivity of the piezoelectric device were extremely interesting!

Nice work, as usual.

L Cottrill

Ainis
Posts: 30
Joined: Mon Aug 25, 2008 10:51 am
Antipspambot question: 125
Location: Lithuania

Re: Been a while - new project, T04 Gas Turbine.

Post by Ainis » Thu Oct 02, 2008 4:00 pm

Ash, I cant understand how you can find heavy side with your balances? Maybe you can tell me?

Post Reply