Johansson´s Pocketbike

Johansson · Post by **Johansson** » Wed Jun 06, 2007 6:59 pm

I did the modification today and ran it only to find the rotor out of balance, I will have to rotate the compressor wheel 1/2 turn on the shaft and run it again to see if it gets any better. I have some pics of the hole before and after I opened it up, but I am using a borrowed computer at the moment so I will post them later this week.

...apply the same pressure into the tank you were running P2's at...

The problem is that there is a backpressure on the other side of the restrictor that is difficult to simulate, it is P2 minus the combustor and NGV pressure drop. The needle jet idea is interesting, but the amount of lube needed is so small that it will be difficult to do any fine adjusting with a needle jet without either closing the line or flooding the bearings.

//Anders

Ash Powers · Post by **Ash Powers** » Thu Jun 07, 2007 1:24 am

Anders,

Yes, I did overlook that element. :) However, you could still install a small needle valve in the feed line and simply adjust it such that it provides the proper quantity of flow to the bearings and simply leave the needle valve in the setup. I politely disagree in your comment that a needle valve lacks the resolution needed to obtain the proper oil metering. I used a small brass needle valve I got from ACE Hardware in their brass fittings section - it has 1/8" NPT male ports and the thread pitch for the needle shaft is quite fine. The needle shaft is only about 1/8" diameter and I can guarantee you it will work for your app. I used one of these in my T25 gas turbine to control the liquid fuel flow to the combustor - placed just after an automotive fuel pressure regulator which is fed by the fuel pump. It worked like a champ and I could very precisely control the fuel flow rate to the engine. You'll accomplish the same thing without having to go through the labors of any mathematical analysis/guesswork or labors of making restrictors with a trial and error approach (time consuming unless you get lucky).

You probably should source a turbocharger rebuilding shop and take your rotating group to them to have it balanced and indexed so you can properly orient the compressor wheel and nut to the turbine shaft.

Or, you could simply use the method described in Thomas Kamps book - it actually works pretty well; it is the method I used to balance my current T04 GT.

Johansson · Post by **Johansson** » Thu Jun 28, 2007 5:05 pm

It can also be a flooded rear bearing that is making the noice since I never milled the drain slot under the rear bearing as John suggested earlier.

I will just have to keep on testing different things until I find the cause of the vibrations and noice, since my goal is to have it running before I retire I have plenty of time for tweaking (~40 years or so...) *laughing*

//Anders

Johansson · Post by **Johansson** » Thu Jul 05, 2007 8:05 pm

I found some pics of the modification that I made.

racketmotorman · Post by **racketmotorman** » Fri Jul 06, 2007 6:14 am

Hi Anders

That'll let some cooling air flow thru :-))

Cheers
John

Johansson · Post by **Johansson** » Tue Jul 17, 2007 4:43 pm

I decided to do a couple of tests today to find out what is causing the vibrations.

First I tried to rotate the compressor wheel 180 degrees on the shaft and found the same bearing noice and vibrations when running the engine, so it is not likely that compressor wheel dislocation is the cause.

After that I disconnected the lube line and ran the engine without lubrication, first 10 seconds on idle so the remaining lube had time to exit the bearings and then a quick throttling which again caused a whining noice and vibration so I turned off the engine before the bearings could take damage from the loss of lubrication. The exhaust puffs disappeared quite naturally.

It is so strange, when I ran the engine this spring with less lubrication it ran perfectly until the rear bearing ball cage broke. I could hear a change in the engine noice instantly compared to previous runs and the engine throttled perfectly smooth with the exhaust jet as the only noice, nothing like it does now. I am very eager to find out what the problem is since I cannot figure out what I have done to the engine after the bearing change that made it run like this...

Bruno Ogorelec · Post by **Bruno Ogorelec** » Tue Jul 17, 2007 8:57 pm

Johansson, I have sent you a private message.

Johansson · Post by **Johansson** » Tue Jul 17, 2007 10:31 pm

I have replied to it now, took a bit of thinking before I wrote it...

Bruno Ogorelec · Post by **Bruno Ogorelec** » Tue Jul 17, 2007 10:46 pm

Johansson wrote:I have replied to it now, took a bit of thinking before I wrote it...

Thank you very much!

Johansson · Post by **Johansson** » Fri Jul 20, 2007 3:47 pm

At last some progress with the bike.

I hooked the oil line up to a container to see how much oil it would flow at idle and just above and it looked ok even though the vibrations were the same as before. When the engine had cooled down a bit I removed the jet pipe and turned the compressor wheel 90 degrees to confirm that the rotor wasn´t out of balance since it didn´t do any difference when I turned it 180 degrees earlier, fortunately I was wrong about that.

I only ran the engine up to 6 psi since I had a rear bearing failure at 10 psi during the last successful run, much less vibrations now which proves that the rotor needs to be balanced again and marked on the shaft and compressor wheel so it can be perfectly aligned after it has been apart. The flame out on the end of clip could have been caused by one of the syringe needles dropping out, they are only soldered in place at the moment.

I am very satisfied with the relatively cool turbine wheel which shows that the combustor is working like it should.

http://www.youtube.com/watch?v=2dGOcpvrB_w

Edit: I took the engine apart this evening to send the shaft and compressor wheel for balancing, and the rear bearing has been running much cooler since I fitted the larger bleed air tube. The inner race is slightly discoloured but the ball cage and outer race still looks like new. It came out freely with preload working which is an improvement since the bearing has sometimes been found stuck in the shaft tunnel earlier during disassembly, probably caused by excessive heat.

Johansson · Post by **Johansson** » Sun Sep 09, 2007 7:35 am

I have been busy moving lately so I haven´t had time to work on the bike for a while, but a couple of weeks ago I found a garage just a few blocks away from my new apartment so next time I visit the village I will take the bike with me.

The shaft has not returned from balancing yet, I will have to call him up to find out what´s the problem...

Johansson · Post by **Johansson** » Fri Oct 05, 2007 2:47 pm

After some waiting I got the shaft back from balancing, this time every rotating part is marked so they can be fitted together correctly later.

I think that I will fit the cheramic bearings before I run it next time, then I won´t have to disassemble the engine core again for a while if the vibrations are gone. If so I can do some tests at higher case pressures and start to build the rev counter, fun fun fun! =)

Sorry by the way for the slow updates, I had hoped to finish the bike this summer but some other interesting projects came in the way...

Johansson · Post by **Johansson** » Mon Oct 08, 2007 8:45 pm

I assembled the engine this evening with the new cheramic bearings, let´s see if they survive longer than the steel bearings did at 10 psi P2.

Since the bearing fit on the shaft is pretty tight it is really annoying to find that every single bearing I have used has a slightly different inner diameter, not more than a few .001´s but enough to make the difference between a sliding fit and a bearing stuck halfway on the shaft...

Next weekend I might have time to run the bike, I´ll try to tape it and put it on Youtube.

Johansson · Post by **Johansson** » Sun Nov 04, 2007 2:19 pm

I ran the bike today, it is vibrating more than ever and flames out above 10 psi P2. I am getting pretty tired of these problems so I am thinking of building a new engine for the bike with lighter parts and a design that is tried before.

Since I´ve spent a fair bit of work on this engine it can seem a bit stupid to put it aside, but it feels better to start from zero with a new engine than to keep struggling with a crappy designed engine (rear preload, steel housings with low tolerances and so on).

//A very disappointed Anders...

Viv · Post by **Viv** » Sun Nov 04, 2007 6:53 pm

Hi Anders

Sorry to hear your having a rough time with this part of the engine, although I am not a turbine guy I and probably a lot of the other pulse guys have been following this project from the edge of our seats since you started.

I have probably learned more practical turbine stuff reading your threads than any other.

If you cant fix this engine or come up with a solution you like I can assure you we will all be waiting to read about the next engine to go on this bike.

Good luck

Viv

www.pulse-jets.com

Johansson´s Pocketbike

Finally!

Edge of the seat!