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TOPIC: Not Tamiya or RC, but very cool!

Not Tamiya or RC, but very cool! 7 years 5 months ago #10189









Ok, not Tamiya or even RC, but I thought some of you might be interested..... (S'pose I could claim that some of the parts have been made from reclaimed Tamiya bits & that's what makes them relevent...)
The green engine is a 4-stroke, spark ignition petrol engine, with a hit-n-miss governor (To regulate its speed). The inlet valve is automatic (Not cam operated) & opens against spring pressure when there's a vacuum in the cylinder (Piston going down, exhaust valve shut). The spring strength is critical to allowing the right quantity of fuel/air in. The exhaust valve is operated by camshaft & pushrod.
The hit-n-miss governor works like this: When the engine is going too fast, the brass weights on the flywheel fly out, & by way of a pair of levers & a sliding collar, operate a latch that holds the exhaust valve open (& disables the ignition points). The engine then freewheels until it slows down. Once it's going slow enough, springs pull the weights back in & unlatch the exhaust mechanism, allowing the valve to close & the engine to start firing again.
The ignition is a battery powered Total-loss electronic unit & lives in the wooden box. I bought it in only because I was struggling to find an ignition coil small enough to not look daft, otherwise I would've made that as well. Spark plug was a bought in too, purely cos it was so cheap it wasn't worth the effort to make.
Lubrication is splash/drip type, via the home-made brass/glass cylinder oiler & the 2x bought-in flip-top main bearing oilers. The crankshaft is hollow with an internal wick, to feed oil from the main bearing oilers to the big-end bearing.
Carburettor is a simple venturi, with a needle valve made from an M2 cap screw with a sewing needle mounted in the end of it.
I built it about 3 years ago, from March to August (Stuck at home on chemo), & EVERYTHING is handmade, except most of the fasteners, the 2x flip-top main bearing oilers, the spark plug & the ignition unit. Yes, I made the springs, valves, piston & rings, bearings, points, gears, camshaft, everything!

Other silver/black engine is a low-differential Stirling engine. Again, all handmade except for fasteners & bearings (Tamiya 1150s). The brass bits started life as the prongs from a 13A domestic plug....
Works like this: The bottom bit is a sealed chamber with heat-conductive top (Cold) & bottom (Hot) plates. Inside the chamber is a wodge of loose-fitting styrene foam (The Displacer) that is connected to the crankshaft by way of a pushrod. The Displacer wafts air about inside the chamber to bring it in contact with either the hot bottom plate, or the cold top plate, depending on the position of the crank. Connected to the bottom chamber is a small glass cylinder with a PTFE piston, which is connected via a pushrod to the other end of the crank.
When the bottom plate is heated, (Or rather, made a higher temperature than the top plate), the air in the chamber is also heated & expands, forcing the PTFE piston up. This in turn rotates the crank, which in turn forces the displacer down. This wafts the hot air from the bottom of the chamber up against the cooler top plate. As the air cools, it contracts & pulls the PTFE piston back down. Crank turns some more & the displacer wafts the now cool air back down against the hot plate for re-heating, & the process continues.
If you plonk the engine on a cup of hot tea, there is enough energy there to run it. It'll also run if you put ice on the top plate instead of heating the bottom plate. The missus has a smaller, more efficient one that she built from a kit, & that one will run from just the heat of your hand, or sat on top of the TV!
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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10191

B) Cool!

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10196

Very cool engineering. A video of it would be great. B)

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10199

I'll see what I can do later - not sure if my new cam does video & my phone cam quality is very poor.
Always tickles me the expression on people's faces when you tell them you ran an engine up in the kitchen!

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10200

Video is a non-event I'm afraid, it appears the new cam's video function is just about as pants as my phone

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10202

I'm sure you could put that IC engine in a car - it's way more advanced than the diesels that pass for RC engines ;)

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10203

Wouldn't work in a car cos it's only got fixed ignition timing & a fixed speed carb. It would probably work in a slow boat though.
It's a design loosely based on the old engines they used to use to drive farm machinery, hence the need to keep a constant speed

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10204

eddrick wrote: Wouldn't work in a car cos it's only got fixed ignition timing & a fixed speed carb. ...


It'd be fine for the Playstation generation - my nephew seems to think there are only two throttle positions on my cars - flat out & crashed :whistle: :S

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Re: Not Tamiya or RC, but very cool! 7 years 5 months ago #10208

Hahaha, yep sounds like my driving too!
Speaking of which, I'm just charging the HSP for some back garden bashing, finally getting around to testing a gearbox mod I did a year & a half ago....

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