Running at 0

"Cé hé sin" (michael-m-mouse)
09/30/2016 at 14:38 • Filed to: Hot bulb engine, Zero rpm

Here we have an engine running at 0 rpm.

“But”, pedants will say “it’s not running at 0 revs. It’s doing about 90% of a rev one way and then another 90% the other so overall it’s doing something like 60 rpm”.

Away with you, pedants. After running for a minute it still won’t have achieved a complete revolution.

Zero rpm.

What puzzles me is how an engine that fires so far ahead of TDC ever gets to run in one direction.

DISCUSSION (20)

Jcarr > Cé hé sin
09/30/2016 at 14:44

I had a lot of fun researching these things after your starting video yesterday. Fascinating machines.

jimz > Cé hé sin
09/30/2016 at 14:45

I’m assuming at the beginning and end he’s manually changing the spark advance.

Berang > Cé hé sin
09/30/2016 at 14:46

Momentum and power.

Cé hé sin > jimz
09/30/2016 at 14:50

Nope. No spark! They’re neither compression nor spark ignition. So far as I know the only adjustment is the amount of fuel flowing.

My theory is that as you add more fuel you’ll need more air to ignite so ignition will take place later in the cycle when more air has been compressed.

I’ve spent several minutes looking up hot bulb technology on the internet and now consider myself an authority thereon.

Cé hé sin > Berang
09/30/2016 at 14:53

Having ignition that early will defeat both though as the engine will be fighting against itself.

My theory is that as you add more fuel you need more air to ignite it so ignition will take place later when sufficient air has been compressed.

jimz > Cé hé sin
09/30/2016 at 14:59

more so than I am. though shortly after posting that I went to the YT page for that video and saw it’s a hot-bulb engine.

Berang > Cé hé sin
09/30/2016 at 14:59

It’s hot bulb though, so effectively the timing is fixed (well relatively speaking) you’ll notice it spins up when he gives it more fuel (priming lever by the flywheel).

Tekamul > Cé hé sin
09/30/2016 at 15:04

I like old motor designs. It’s a nice insight into how to solve a problem when existing state of the art is pretty minimal.

Jonee > Cé hé sin
09/30/2016 at 15:18

Two-stokes can run in both directions. Or, no directions, apparently. Amazing. My Fuldamobil uses one of these Sachs motors, and to go in reverse, you turn the engine off and restart it backwards.

Cé hé sin > Jonee
09/30/2016 at 16:16

Yes, that’s a two stroke thing. The Messerschmitt KR has the same arrangement, you just switch off and then turn the key in the other direction.

Want to reverse your really big ship? Same thing. Reversing a two stroke engine that could be 25,000 litres is a different process. They change the timing of the compressed air starting system so that it slows the engine down and then reverses it.

Interestingly they also build reversible four strokes which use a separate reverse camshaft.

Mercedes Streeter > Jonee
09/30/2016 at 16:31

Do you literally own nothing but awesome microcars? If so, can I move in? lol

Jonee > Cé hé sin
09/30/2016 at 16:54

Yeah, the Messerschmitt had the same drivetrain. Four reverse gears, technically.

I didn’t know that’s how they did it with a ship. Fascinating.

What are the reversible four-strokes used in? Also boats?

Jonee > Mercedes Streeter
09/30/2016 at 16:57

Yup!

http://jalopnik.com/267517/a-quartet-of-microcars

I actually don’t have all those cars any more, sadly. Ran out of room and started to pay back my student loans. But, the Fuldamobil will never leave me. It’s family at this point. I still don’t have the space for a roomie, but you’re welcome to visit any time, Miss M!

Cé hé sin > Jonee
09/30/2016 at 17:22

Yes, it saves the cost of reverse gearing.

Like this you use a camshaft with two sets of cams.

Jonee > Cé hé sin
09/30/2016 at 17:34

Exactly. Same reason Messerschmitt and Fulda did it.

That’s very cool. A clever solution.

torque > Cé hé sin
09/30/2016 at 19:01

Is there any practical purpose in the tractor (lead post video) running back & forth like this, or is it just a neat party trick?

Cé hé sin > torque
09/30/2016 at 19:04

No and yes, in that order!

Stephenson Valve Gear > Jonee
09/30/2016 at 23:12

I used to have a railroad “speeder” - the little four-wheeled car that the track maintenance guys used before they had pickups with the small railroad wheels. My speeder was made by Fairmont, and had a two stroke water cooled gas engine with a manual spark timing adjustment. The drive train consisted of a flat belt running between a pulley on the engine and a pulley on the axle with a tensioner in between that functioned as the clutch. To run in reverse, the engine was started backward and the timing lever advanced in the reverse direction. With a bit of practice, the engine could be reversed without cranking by shutting off the ignition, giving it a quick choke while the engine was slowing down, then kicking on the ignition just as the engine was approaching TDC for the last time... the timing lever was left in the “advanced” position the entire time, and at the ultra slow speed the engine would fire and kick off running in the opposite direction, the timing now becoming very late instead of a bit advanced. Let the engine speed up a bit, adjust the timing, tighten the clutch and off you go! Lots of fun...

Jonee > Stephenson Valve Gear
10/01/2016 at 00:10

That does sound like fun. And hilarious.

There was a company in Germany back after the War that made speeders that once tried making a road car. It didn’t go well.

http://oppositelock.kinja.com/wendax-possibly-the-worst-cars-ever-made-1754435831

Stephenson Valve Gear > Jonee
10/01/2016 at 21:01

Very interesting reading! I enjoy learning about oddball, underdog type machinery. Of course, with a name like Wendax, I would expect it to have perpetually clean windows...