More free plans: 40 pound Chinese

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metiz
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Re: More free plans: 40 pound Chinese

Post by metiz » Sat Jan 02, 2016 9:35 pm

https://www.youtube.com/watch?v=jkleN5x ... uscomments
New M40 build to celebrate the new year
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Re: More free plans: 40 pound Chinese

Post by Mike Everman » Sun Jan 03, 2016 2:55 am

Nice! That sucker is getting very hot. You may have to switch to titanium. :)
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Re: More free plans: 40 pound Chinese

Post by tufty » Sun Jan 03, 2016 4:52 pm

Niiiiice.

Happy new year.

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Re: More free plans: 40 pound Chinese

Post by metiz » Sun Jan 08, 2023 7:19 pm

Quantify the world.

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Re: More free plans: 40 pound Chinese

Post by Mike Everman » Mon Jan 16, 2023 5:32 pm

Great! Nice run to start a year that can only be better than last year!
I gotta get out and make some flame and noise. Thanks for the inspiration.

Hope all is well otherwise, Joost!
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Re: More free plans: 40 pound Chinese

Post by Redstone » Fri Nov 10, 2023 9:11 am

I have built this engine and over the past week have been trying to get it to start up, with no success.
The first obstacle I encountered was hooking up the engine to a propane cylinder. I couldn't find any POL fittings that adapt to 3/8 LH UNF, or any other common fuel hose fitting, and so the best I found was a high pressure (4.5 bar/65 psi) LPG regulator. However with the regulator and cylinder valves fully open the gauge only reads ~20-40 psi. I've seen people suggest that a regulator may hinder pulsating combustion by responding to pressure changes and lowering the output pressure.
Not using a spark plug for now, perhaps an ignition source in the chamber would be better than the intake/exhaust.
I am using two compressed air guns to shoot up each intake (to prevent the flame just shooting out one of them) as an air supply to get the engine started. Moving the air guns too far up the intake tends to result in flames spewing out the intake, combustion moving out of the chamber and to the exhaust pipe, or the engine flaming out.
Does anyone have any ideas on how this setup could be improved?
Video of startup attempt, I apologise for being in the way of the camera: https://youtu.be/AfBVAYxMX4c
Attachments
IMG_20231108_134721.jpg
Reads between 20 and 40 psi fully open during testing.
IMG_20231108_131531.jpg
Injectors are ~65mm deep. Soot is from acetylene torch.
IMG_20231107_131840.jpg
Coil to heat up the propane. Could this be working against me?
IMG_20231107_130353.jpg

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Re: More free plans: 40 pound Chinese

Post by tufty » Fri Nov 10, 2023 5:08 pm

That doesn't seem to be close, it's not barking, popping, or howling. When you're getting close, you should be getting the sort of bangs that make you soil yourself, especially with an engine of this size.

Regulators are usually a problem in terms of flow, not in terms of pressure. I think this may well be a major part of the problem you're having.

Next up, I know bugger all about running twin inlet engines, never done it. But apparently this will run from one inlet (see earlier in the thread), so I'd suggest blocking one inlet and then playing with a rosscojector to see if you can get it to start to resonate, at least. Take a piece of the copper tube you're using for fuelling, cut at 45° with side cutters and very slightly opened up use this as a "fire wand" - turn on the gas, light it up (be aware that this will give you a very big agressive flame, do not do this indoors), and feed it in and out of the inlet to play with fuel positioning.

Also, the flares on the inlets look, to me, horrible. It is, in my experience, quite important that inlet flares are smooth, but on the other hand I've never played with ones like you have.

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Re: More free plans: 40 pound Chinese

Post by metiz » Fri Nov 10, 2023 8:11 pm

Hi Redstone, welcome to the forum

I have some notes:
1: Lose the regulator. You will never get this engine to run without full flow from your propane tank
2: Looks like you MIG welded your engine. Try spot-welding the slits you have at the end of your intakes closed and then file the welds smooth on the inside
3: Figure out a way to make your injectors adjustable. I do this with a sliding rail (see image). You may need to fiddle with the depth and you can't do that now
4: Although not necessary, it helps if you ignite the engine from the combustion chamber. Light a firework sparkler and throw it through an intake into the combustion chamber

What is the diameter of your fuel lines?
What kind of injectors do you use? (Rosscojector, GRIMjector, straight line etc)
Personally, I have never gotten this engine to start with an air compressor. The medium speed and high volume air from a leaf blower works best. That doesn't mean you can't start it with an air compressor, but it definitely helps.
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Re: More free plans: 40 pound Chinese

Post by Redstone » Wed Nov 15, 2023 8:24 am

Thanks for the suggestions. I have made an unregulated LPG adaptor, added a spark plug to the back of the combustion chamber, and welded the gaps in the intake flares and filed them relatively smooth. I'm still having some trouble getting it to start. In metiz's videos the pops and bangs sound a lot sharper than what I'm getting. Not sure if I need to modify the engine any further, or if I just need to get better at my starting technique. Any feedback is much appreciated. My injectors just feed gaseous LPG through straight pipes (single exit holes) into the intakes.
https://youtu.be/jgKyDbYWOjg
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IMG_20231115_155516.jpg

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Re: More free plans: 40 pound Chinese

Post by metiz » Wed Nov 15, 2023 2:45 pm

Good job on the flares. It looks like you are still not getting nearly enough fuel to your engine. Are you using a full, or fairly full propane tank? What's the temperature over there? If it's freezing, you might not be able to start the engine even with a full propane tank. Something I would not advise doing, and something I have definitely never done myself, is heating up your propane tank with some fire. Definitely never do that *cough*

Try popping off the extension from your leaf blower so you can one-hand it. Then you can regulate the gas yourself with the other hand and get a feel for it. I usually let it gurgle a bit to heat it up and then close and quickly fully open the gas valve while applying air to start it. I can't emphasize enough how much gas you need. When you think "surely this is enough", it definitely isn't.

My engine has 5mm internal fuel lines, with Rosscojectors at the end, 92mm down the intakes.
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Re: More free plans: 40 pound Chinese

Post by Redstone » Thu Nov 16, 2023 2:16 am

I have the propane valve fully open during these tests. One thing I'm curious about is the ratio of propane to butane other people who have successfully started this thing use. Here they sell 60:40, meaning the mixture only has a vapour pressure of about 70 psi at 20c, whereas 100% propane has a vapour pressure of over 100psi at 20c. It's summer here so it isn't very cold.

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Re: More free plans: 40 pound Chinese

Post by tufty » Thu Nov 16, 2023 11:43 am

Over here in communist frenchystan, if they sell it to you as propane, it's 100% propane (I checked the MSDS for my supplier, nothing special, this is supermarket forecourt stuff). There are small bottles of propane / butane mix sold for eg blowtorches, but they are marked as such. If you're running mix, that might not be helping you, you will almost certainly be needing more gas.

My guess as to your problems, though, are that you're not getting good mixing. a straight nozzle mixes horribly (well, mostly, it doesn't mix very much at all), and if you're running 60:40 that won't help either. How the gas mixes is also very much dependent on where your nozzle(s) are placed, and there's no real good rule of thumb I know of to determine that - you have to be able to adjust that position.

Even with 60:40 you should be able to get it to bark even if it won't run; it's not doing that on the video clips you've shown so far.

Mark would probably suggest chucking some methanol in the chamber, swilling it about a bit, and lighting it off :)

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Re: More free plans: 40 pound Chinese

Post by Mark » Sat Nov 18, 2023 4:42 pm

tufty wrote:
Thu Nov 16, 2023 11:43 am
Over here in communist frenchystan, if they sell it to you as propane, it's 100% propane (I checked the MSDS for my supplier, nothing special, this is supermarket forecourt stuff). There are small bottles of propane / butane mix sold for eg blowtorches, but they are marked as such. If you're running mix, that might not be helping you, you will almost certainly be needing more gas.

My guess as to your problems, though, are that you're not getting good mixing. a straight nozzle mixes horribly (well, mostly, it doesn't mix very much at all), and if you're running 60:40 that won't help either. How the gas mixes is also very much dependent on where your nozzle(s) are placed, and there's no real good rule of thumb I know of to determine that - you have to be able to adjust that position.

Even with 60:40 you should be able to get it to bark even if it won't run; it's not doing that on the video clips you've shown so far.

Mark would probably suggest chucking some methanol in the chamber, swilling it about a bit, and lighting it off :)
Ah, the simplicity of a meager spark and no starting air.
https://www.youtube.com/watch?v=NU3cQ8_upWk
But I can only guess it would be a long shot with something of size.
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