Another Rupnow Air Hit n Miss Engine

[bmac2]

Hi Chuck
Well it’s running, and it hits, and it misses. . . . What it’s doing is about a 3 second run at high revs (I don’t have a tach) before the governor kicks in, then free spins for around 5 seconds dropping almost to a stop before the governor drops out. Everything appears to be moving smoothly with no binding. Having the governor kicking in late to me would be either the spring it too strong or the weights are too light. But wouldn’t it be the reverse for free running too long?
I was going to start to experiment with adding weight to the arms to get them to kick out at lower rpm.
Heaver weights and a stronger return spring?

 

[cfellows]

Seems to me there is something else going on. From your description, it sounds like the governor is having trouble engaging the cam. I suspect that the strong spring is making it rev pretty high, but the governor is having trouble engaging the cam when it slows down. I would suggest a weaker spring and maybe introducing more clearance on the cam engaging mechanism.

Are you running at maximum air pressure from your compressor? When the engine does hit, it needs to get a pretty good boost from the air source.

Chuck

 

[gus]

Hi Bob,

Congrats. You got the H&M going.

Taking a diversion break & building a 80mm RT..RT is straight forward project and very forgiving
if I goofed.

 

[Brian Rupnow]

I like your hemostat idea. I wrap a piece of masking tape around the cut off end and then it doesn't fly across into the parallel universe never to be seen again. They get too hot to just hang onto with bare fingers.---Brian

 

[bmac2]

I like your hemostat idea. I wrap a piece of masking tape around the cut off end and then it doesn't fly across into the parallel universe never to be seen again. They get too hot to just hang onto with bare fingers.---Brian

Thanks guys
I think that when we set up machinery in a room, something about the placement/mass/ magnetic field causes an intermittent vortex into another dimension to open. In my last Mensa Moment I was doing an autopsy on the head after bending the valve pin. The oil on the slave exhaust valve wouldn’t let it slide out. Then that little Murphy's Law voice in my head said “I know. I’ll just give it a little air” . . . . . It’s a simple piece. Only took a couple of minutes to make a new one.
I’m going to disassemble the governor and give everything a close look tonight.

 

[motoseeya]

That is a very nice engine you have their. I think I would like to try one I like air engines ic engines are to much $$$ for elec. parts for a model that will only run 1 or 2 times and then just look at. And this is not your first rodeo I think . Very nice work.

 

[Brian Rupnow]

Motoseeya--The electrics for a points style ignition which include points, condenser, and coil cost about $75 IF---you have a battery all ready.

 

[bmac2]

Seems to me there is something else going on. From your description, it sounds like the governor is having trouble engaging the cam. I suspect that the strong spring is making it rev pretty high, but the governor is having trouble engaging the cam when it slows down. I would suggest a weaker spring and maybe introducing more clearance on the cam engaging mechanism.

Are you running at maximum air pressure from your compressor? When the engine does hit, it needs to get a pretty good boost from the air source.

Chuck

Chuck! . . You where spot on Thm:. Thank you
Took a methodical approach to this, with a lot of disassembly/assembly going on. Used Brian’s trick from his build log and mounted the governor flywheel to a short shaft held in a cordless drill. Cleaned up and refitted the components trying one thing at a time. It reminded me of installing an old-school internal modem. Set the IRQ /DMA dip switches, install, boot up, and repeat.

In the end I think what made the difference was a small rough spot on the crank where the sliding cam rode. I polished it out with some emery. And reducing the return spring pressure.

It’s too cold in the garage to run the compressor today so I used the portable air tank in the shop. It wasn’t toped up but I gave it a try. I’m quite happy with the duty cycle and in the video it’s running on about 30lbs pressure. I still have to true up the flywheels, and it might be a while before I can paint it, but for me this video is 43 seconds of pure joy. I could watch this all day . . . . . apparently for my wife. Once is enough.
:redface2: Arrrgh. . . Photo Bucket is “currently conducting some unplanned maintenance”. Didn’t the Titanic experience “some unplanned maintenance”? I’ll try to get the video up later.

 

[cfellows]

Chuck! . . You where spot on Thm:. Thank you
Took a methodical approach to this, with a lot of disassembly/assembly going on. Used Brian’s trick from his build log and mounted the governor flywheel to a short shaft held in a cordless drill. Cleaned up and refitted the components trying one thing at a time. It reminded me of installing an old-school internal modem. Set the IRQ /DMA dip switches, install, boot up, and repeat.

In the end I think what made the difference was a small rough spot on the crank where the sliding cam rode. I polished it out with some emery. And reducing the return spring pressure.

It’s too cold in the garage to run the compressor today so I used the portable air tank in the shop. It wasn’t toped up but I gave it a try. I’m quite happy with the duty cycle and in the video it’s running on about 30lbs pressure. I still have to true up the flywheels, and it might be a while before I can paint it, but for me this video is 43 seconds of pure joy. I could watch this all day . . . . . apparently for my wife. Once is enough.
:redface2: Arrrgh. . . Photo Bucket is “currently conducting some unplanned maintenance”. Didn’t the Titanic experience “some unplanned maintenance”? I’ll try to get the video up later.

Glad you got it sorted, Bob. It's always a joy when things come together. Looking forward to the video...

Chuck

 

[bmac2]

Forget it. Photo Bucket has been down for more than 24 hours. The guy they sent to Radio Shack for parts must be on a bicycle without a light. Faster to just set up a YouTube account.
I have to think that after a couple of oscillating engines, and working from Brian’s plans, this would be an excellent build for people new to the hobby, especially if it was built without the governor. The machining is straight forward and relatively forgiving. The parts are small enough to be done on a small lathe, yet large enough to work with comfortably. The milling operations could be done in a 4 jaw, or with careful setup, clamped to the cross slide, or just filed. Chuck, thank you for an excellent design. Brian, thank you for all your work putting the drawings together. This was a fun build.

The “Chuck Fellows Horizontal Single with a Liney Halo Valve and hit and miss governor”. Now that’s a handle.

[ame="http://youtu.be/MCBzBgPmtik"]http://youtu.be/MCBzBgPmtik[/ame]

 

[Heffalump]

Wow such a great sound! I do love a hit and miss.

 

[wagnmkr]

Excellent Job!!! I also love the sound!

It looks well finished, and I agree that it is fun to watch it.

That one is on the to do list for sure.

Thanks for the show.

Cheers,

Tom

 

[Brian Rupnow]

Well Done--Excellent build documentation and results,---Brian Rupnow

 

[bmac2]

Hi Gus. Thanks
That’s something I’ve been thinking of myself. I have a Craftex CT133 mini mill, same as the Grizzly and Harbor Freight machines. It can be a challenge finding stuff that isn’t either bigger or costs more than the machine itself.

 

[cfellows]

Nice build, Bob. The engine runs good, but it sounds like the air flow is a bit restricted when it's freewheeling plus it seems like it should coast longer between "hits". Are you sure the slave valve is completely clearing the port into the cylinder during the exhaust cycles? You might try substituting a loose fitting ball bearing for the piston style slave valve. They seem to work a little smoother and don't require as much travel when moving from one side of the cylinder port to the other.

 

[bmac2]

Ya. It’s a little weesey. The hole at the bottom of that “stack” is only 1/8” and now that it’s running I’m going to open it up. I haven’t had a chance to try it on full pressure yet. The compressor isn’t happy under 0 celsius. Once I get it running above 30 lbs. I think the freewheeling will improve. The governor was still kicking in until the tank dropped below 15 lbs. Just stops at 5.