Discussion in 'A Work In Progress' started by sorveltaja, Sep 4, 2008.
Very nice so far, super ambitious....that's what we like
I'm very excited to see your progress and how this works out.
I'm particularly interested in the Piezo-Electric igniter. What kind is it and where are you getting it from?
Also, what are the bore and stroke of your scaled down engine?
Re: PTFE insulated Spark Plugs.
If you have access to it, there was a write up in Model Engineer 5 July 1991 on the subject.
Plug Thread was 5/32" x 40 tpi.
Might be interesting to you.
Great innovation with the coins and much food for thought :bow:
That looks like some very good work..... Keep those pictures coming!!!!!!
Very nice work, I am looking forward to see how the piezo works out, seems much simpler than coil/ battery.
I have been watching this unfold, but haven't chimed in until now. This is an interesting build. Thanks for taking us along on the journey!
BTW Hang in there, you'll figure out your ignition! When there's a will, there's a way.
W/E is right.....As a good friend said to me on a particularly tough build....keep going your doing fine, you'll figure it out.....And I did.
So will you.
Keep at it mate, what I know about electricity could be written on the back of a postage stamp ???
I'm sure you'll figure it out and when you do, perhaps I can make something other than a diesel, (assuming the one I'm making works). :
............... RIP faithful Multi Meter ....... look on the bright side, you are here to tell the tale, guys, please all be careful out there with electrickery, it can bite
sorveltaja, this is a good thread, please make sure you stick around to keep it going ;D
Good to hear, looking forward to seeing the completed version .............. gotta say it does seem incredibly small, very well done for working at that scale.
lol I like the idea of the spark plug
I am not to sure my self on what you were woundering what will happen to the PTFE in the part dirgram yo made, but I know that PTFE is great at high friction and high heats, well thats why they use the stuff on non-stick pans.
Great work! I didnt realise the scale of it until I saw that 9V battery, Cant wait to see it run.
How sure are you that you're piston isn't letting some air out around it?
I've built engines where I was pretty sure the piston was airtight only to find out that adding rings or o-rings greatly improved the compression.
Wow, that is on a small scale. I'm glad you've left the piezo ignition idea, I was keen to see how you got on with it however, I remember seeing some comments by Jan Ridders that it takes a lot of power to drive them. In fact, on his vertical 2 stroke engine with a much larger cylinder bore and stroke than yours he had to resort to a circuit with coils and a roller micro switch operated by a cam. It takes much less force to drive it and looks neater.
Love the spark plug idea, I would be aiming for a CR of at least 5:1.
I am just trying to throw a few things out to possibly look at, so if you have, then please ignore.
It the vlave timing right? In other words, is the intake valve opening when the piston is travelling away from the valves to let the air in the cylinder? If it isn't, you won't get much compression if at all because you aren't filling the cylinder with air. The exhaust valve must be closed during the compression stroke or the air will simply leave the cylinder. Another thing that seems to be a potential issue is the valve seats. Are the valves sealing on the seats? And the last item is the valve body and the cylinder... Is that connection air tight?
How much clearance do you have between the piston and the head at top dead center? If you have an abundance of space left over in the cylinder, the compression will certainly suffer.
If all of the valves seal, and the timing is right, the piston seals to the cylinder walls, and your compressed volume is narrow, then you should have compression. Somewhere there is a leak. You might be able to use some soapy water to find it.
What does the compression ratio of your version work out at? It's the swept volume / dead space I think! Or is it swept volume + dead space / dead space? Can't remember!
Very nice looking fuel tank. I am getting anxious on this one! Keep up the good work!
Reminds me of those boys in thier 1.1 litre Citroen Saxo's (compacts for our friends in the U.S) with 8" exhaust tail pipes! ;D Kind of suits this little one though, it's looking great.
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