Calculating top speed on ice...

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Johansson
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Re: Calculating top speed on ice...

Post by Johansson » Fri Jul 31, 2009 9:23 am

GRIM: Ok, good to know that I am not the only one having problems with this. Fortunately the race is 6 months from now so I´ll be damned if I can´t get it sorted out until then.

M: I haven´t changed anything from the last run, what the video clips showed was our only successful starts so the truth is that we struggled very hard to get it running even that time. The reason why I didn´t want to run it on liquid propane now was to keep the vapour coil hot, with liquid propane the coil freeze and wont be able to vapourise any fuel at all.

So there is a modification on its way? This engine is supposed to be used up during the testing anyway so I´ll build a stainless version later when everything is sorted out.

Eric: Interesting injectors! Until the engine mods are published I will make the dual nozzle for the leaf blower and a couple of different injectors to try starting with M´s injector, the aerospike and SR-71 injector both look interesting and doable on my lathe (without my mill the tornadic injector will be hard to make) so if you would send me the drawings I would be thankful.

milisavljevic
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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 9:43 am

Hejsan Anders!
Johansson wrote:I will build a pair of M´s superdeluxe injectors before the next test...
If you do not have a 3,5 mm drill bit, then I suggest that you start off with MFI injectors sized to ID 3 mm.
You can always bore the channels out to ID 4 mm, provided the channel lengths are approx. 20 mm (5x ID).

If you have any questions about the plans, just let me know. Meanwhile...have a nice weekend in Norway! :D

Cheers,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by Johansson » Fri Jul 31, 2009 9:53 am

milisavljevic wrote: If you do not have a 3,5 mm drill bit, then I suggest that you start off with MFI injectors sized to ID 3 mm.
A 3.5mm drill I have so no problem there. No more work on the engine for a week or so, I figure that it by then will be quite ashamed of itself and behave better the next time I take it out of the workshop. :mrgreen:
milisavljevic wrote:Meanwhile...have a nice weekend in Norway! :D
Vielen dank! 8)

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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 10:03 am

Hej!
Johansson wrote: The reason why I didn´t want to run it on liquid propane now was to keep the vapour coil hot.
If it will not start from vapour feed, then for sure the injector area is too small. I have seen this before.
The starting behaviors you described match to undersized injectors...what is the ID of the supply lines?
Johansson wrote: So there is a modification on its way? This engine is supposed to be used up during the testing anyway so I´ll build a stainless version later when everything is sorted out.
You bet. I will close the loop with GRIM and get a drawing off to you. If you want to modify the existing
engine first, I could work out a different drawing showing how to mod the engine in place (not difficult).
Ideally, the transition cone should be replaced, but the change is small enough to work around for yours.

Before making changes, you should try larger injectors. Why not use GRIM's three-pointers*? They work.

Cheers,
M.

*Check GRIM's thread, or send him a PM for details. Each fuel probe has three (3) ID 2 mm orifice ports.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 10:07 am

.
Johansson wrote:Vielen dank!
Gern geschehen!

M.

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Re: Calculating top speed on ice...

Post by Johansson » Fri Jul 31, 2009 10:41 am

milisavljevic wrote: If it will not start from vapour feed, then for sure the injector area is too small.
Exactly our thought, with the bottle inverted the injectors could flow massive amounts of propane but with gas feed the injector area might not be large enough. The ID of the fuel lines is 5mm.

The blower mod should also improve starting since half of the injected fuel is blowed right out of the intake, if not it will keep the holder happy since there will be no more murderous flames coming from the intakes. After all, we do have our beloved beards to think about. 8)
milisavljevic wrote:Before making changes, you should try larger injectors. Why not use GRIM's three-pointers*? They work.
I will build new injector lines from hydraulic tubing with threaded ends so I can try different injectors at the test place, I´ll figure out what designs to try and order some material.

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Re: Calculating top speed on ice...

Post by Johansson » Fri Jul 31, 2009 11:04 am

Eric wrote:Holy crap, I'll get working on drawing up those injectors for you right now. What is the fuel tube ID and OD?
Forgot to answer this, the copper tubes are 5mm ID and 8mm OD but I can change them if needed.

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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 2:10 pm

Hejsan Anders!
Johansson wrote:The ID of the fuel lines is 5mm.
Ummm...Okay. That is a bit on the too small side. After the "T" (ie., supply line splitter), as you move back
towards the bottle, what is the supply line ID? Please do not tell me that it is also ID 5 mm. This is too small.

Tim ("wakmat") had this exact same problem. The injectors were smallish, but not pathetically so, but they
were being fed by way too small a feed line. No point in wasting another minute on starting attempts, mate.

Once we changed out to larger supply lines...his Thunderlite started on the first try. It can be done, Anders. :D

What have you got that is bigger than ID 5 mm?

Cheers,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 2:19 pm

Anders,

Please confirm with GRIM, but I am pretty sure he modified his blower to feed both intakes simultaneously.
Without success. The ginormous flames, etc., are more a symptom of the restrictive fuel delivery system.

Cheers,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by Johansson » Fri Jul 31, 2009 2:27 pm

Yup, the same 5mm ID propane tubing all the way back to the bottle. I can easily change this to a tube with larger diameter from the local plumbing store, it is 8-10mm ID if not even larger but I don´t remember exactly.

It would be great if the problem is so easily solved, I´ll do the injector test anyway since the crimped copper tube injector is a pretty lousy design considering the alternatives discussed here in the thread.

Ok, if I remember it right he wrote something about his blower in his thread so I´ll read through it. I still need to make a new nozzle for the blower since the regular plastic one is partially melted...

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Re: Calculating top speed on ice...

Post by milisavljevic » Fri Jul 31, 2009 3:00 pm

Hej!
Johansson wrote:I can easily change this to a tube with larger diameter...it is 8-10mm ID if not even larger.
Anything in that diameter range will do nicely, mate.
Johansson wrote:It would be great if the problem is so easily solved.
And it sure will feel good when it starts up next time! :D


"A pulsejet without an adequate fuel delivery system is but a poor excuse for a doorstop.
. A fuel delivery system without a decent pulsejet is but an excuse away from pyromania."

--- As translated from the original Pirate by Cap'n M.'s yeoman, who was sober at the time.


Have a safe trip. Catch you on the flip side.

Cheers!
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by Johansson » Thu Aug 06, 2009 7:55 pm

A pair of MFI injectors are made and fitted to the engine, they are made with a 3.5mm bore and close to specs except for the inner radiuses (is that really a word?) which I didn´t have tools to make on my lathe. some different angled cuts will have to do. I won´t post any pics of it with respect to M´s wishes.

I fitted a threaded injector mount on the copper tubes (I measured them today and found that they were 6mm ID, not 5mm as I earlier wrote. I will keep them for now, will get back to them if the injector change won´t get the engine running.) so before I do another test I will make at least one more pair of injectors so I can try different designs at the test location, I have to borrow a trailer and drive the kick 20km away from the workshop to test it so I would like to try as much as possible while I am there.
Sparken 120.jpg

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Re: Calculating top speed on ice...

Post by milisavljevic » Thu Aug 06, 2009 10:30 pm

Hejsan Anders!

Welcome back.
Johansson wrote: They are made with a 3.5mm bore and close to specs except for the inner [radii]
...some different angled cuts will have to do.
If possible, please try to grind down (smooth out) the angles with a suitable hand tool (eg., a Dremel link).
Johansson wrote: I found that they were 6mm ID, not 5mm. I will keep them for now.
I think you are skating on very thin ice with your supply lines (even ID 6 mm), but it is your time to waste.
If you would at least consider having a replacement set of fuel lines handy, while you are out in the field... :?


When insufficient fuel is available (eg., due to line restrictions), the tendency is to jet it into the intakes
at higher velocities (an intuitively reasonable, but mistaken idea). The jets excite an open-pipe acoustic
mode in this duct between the intakes and tailpipe (bypassing the combustor, much like a "short circuit").

The new tail-couple (dims are ready now) will suppress the mode, to allow much easier starting attempts.
This has been tested and proven with Tim's ("wakmat") Thunderlite, so it's a straightfoward replacement.

You will be able to implement this revision on your stainless pulsejet. :D

Cheers,
M.
no safe haven for merchant scum


for ye merchants who do the prop'r t'ing only if
ye be haul'd-up on charges b'fore ye ship-mates
an' threat'nd wit' forfeiture of all ye precious loot
hear this - so-called stand-up guys YE BE NOT

avast!
Cap'n M.

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Re: Calculating top speed on ice...

Post by Johansson » Fri Aug 07, 2009 8:31 pm

I did another test this evening with much better results, as long as the propane bottle was hot enough the engine started pretty easy with M´s MFI injectors 6cm down the intakes.

I used gasoline for the test and almost got it to run on liquid fuel alone, some gas flow was needed for the engine to run but it wasn´t much so I am confident that I will have it running on 100% gasoline soon. I opened up the 1mm restrictor a bit since I couldn´t get it to flame out even at full throttle, but at that time the bottle pressure had dropped so much that I couldn´t get it started. That marked the end of test no.3. :wink:

Pics and videos might be posted as soon as possible, my friend will upload the files to a memory stick and hopefully remember to bring it to me tomorrow. The weather was great so we had a good time making noice today. 8)

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Re: Calculating top speed on ice...

Post by Johansson » Sat Aug 08, 2009 7:12 pm

Mike Everman wrote:I look forward to seeing that, Anders! I hope the pissing match is overnow and we can get on to watching your tests and progress.
I hope so too.

At least I have gained some experience running this engine now so hopefully there won´t be any unsuccessful runs from now on, the next time I hope that I can get the engine to sustain on liquid fuel and take a thrust reading so I know how much of its potential I am reaching.

When I ran it yesterday on both propane and gasoline it pushed really hard against the tiedowns so with some more tuning it should prove to be a kick-ass engine! 8)

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