Run in stand/dyno build.

[Terry Keeley]

Terry your test stand/dyno is well constructed to run dead true. Your test motor is mounted to align perfectly with it and everything is rock solid. The only thing is, that any single cyld. 2 stroke engs.' crank, is trying to move all over the place. The motor should be constructed to have slight end play, they vibrate/harmonic at various RPM, and good RC engine brgs. have internal clearances that don't hold the crank at dead zero as they run; they are not suppose to. It's great to have everything within a tenth, but from the motor to the stand, you need to allow some "give". This will also allow the motor to operate closer to an "as in the boat" configuration, and not have it fighting the stand. Rubber isolation motor mounts, slightly flexible joiner, or both. I'm not sure that clutch is doing anything, as the fan seems to be rotating even as the starter motor is spinning over. I'm sure the idle RPM has that clutch fully locked up. You may be able to lighten the centrifical OD of the "shoes" to raise the engagement, or change to a more adjustable clutch if you need one.

You and Charles are right for sure, if I was running an electric motor my setup might work but I guess the crank whips around way more than I thought throwing that big clutch unit out of whack. I was thinking a tight fit between the male/female parts of the ball joint would support it but guess I was wrong. I'll need the clutch/one way bearing more when I run this as a dyno, it's not really needed now but I'm getting some good testing in with the fan.

I checked the shaft balance, seems pretty good. I'm not completely convinced if I just put a flex shaft or rubber mounts in there it will solve my problem, I think I might need another pillow block to support the other side of the clutch. Or another bearing in the clutch housing, the way it is now the shaft is only supported by the one way bearing.

Rome wasn't built in day I guess, lol.

 

[dave roach]

Terry
Watch the the last video at the end and the shaft is flexing at the one way clutch.

Dave

 

[Terry Keeley]

Terry
Watch the the last video at the end and the shaft is flexing at the one way clutch.

Dave

Yup, I set up the camera to look at the clutch and does it ever move around!

Been looking at it a bit and am thinking of putting a bearing/pillow block right on the OD of the female U-joint.

 

[Dennis Somers]

Terry please be VERY CAREFUL in regards to the clutch. At elevated RPM, the drum appears to be "bell-mouthing" at the motor end from the weights centrifical pressure. I don't believe this clutch is designed for the RPM of nitro, and I would hate to see it grenade itself. I don't want to sound negative, but it's not worth getting hurt over.

 

[Terry Keeley]

Terry please be VERY CAREFUL in regards to the clutch. At elevated RPM, the drum appears to be "bell-mouthing" at the motor end from the weights centrifical pressure. I don't believe this clutch is designed for the RPM of nitro, and I would hate to see it grenade itself. I don't want to sound negative, but it's not worth getting hurt over.

I hear ya, just wait til I swing 40 lbs of steel to 30K.

The video sure is telling, you don't see 10% of that standing above it while it's running. If you watch the second vid carefully it looks like the whole unit is going through several harmonic stages.

 

[Charles Perdue]

On one of my many trips to the K&B factory, Bill Wisniewski called me back to his little shop and told me he wanted to show me something.

He started an engine that he had on his test stand, turned out the lights and used a strobe light on the engine. If I had not seen it with my own eyes, it was almost unbelievable as to how much the engine case and front snout were distorting and moving around at full load and speed. You would not think that the engine would even run moving about that much.

Charles

 

[John Beardslee]

On one of my many trips to the K&B factory, Bill Wisniewski called me back to his little shop and told me he wanted to show me something.

He started an engine that he had on his test stand, turned out the lights and used a strobe light on the engine. If I had not seen it with my own eyes, it was almost unbelievable as to how much the engine case and front snout were distorting and moving around at full load and speed. You would not think that the engine would even run moving about that much.

Charles

For sure Charles! Back in 1970 or 71 I used a strobscope on a series 70 pylon engine in a test stand and the entire jug danced all over the place. I call John Brodbeck ( owner of K&B) about what I observed. His comment was: he didn’t care, the airplane guys love them and he sells a lot more to them than the boat guys. I switched to Super Tiger G40 abc as soon as it came out and never looked back. I continued to talk to John at the Toledo show for years and did many props for Bobby Tom who worked for K&B. John was sure slow to make changes, if Clarence Lee or Bill Wisniewski had been a model boater things might have changed.

 

[Terry Keeley]

My Consigliere came up with a simpler solution to support the other end of the clutch, that is to basically make a bell housing with a bearing to fit the U-joint and bolt it to the existing pillow block.

We think it's the clutch being out of balance when it locks up that's causing it and just too much weight hanging off the shaft unsupported. Possibly also some movement from the motor.

If the can still moves around it'll prolly be time for a flex cable/rubber mounts etc. or a re-think of the whole clutch unit.

Gonna take a little break from this and run a boat or two, been pretty solid on it for three months.

 

[Charles Perdue]

Hello Terry, sometimes I also do my best thinking when I step away from a project for a short time.

Just to clear things up a little about the cable drive, It acts like a spring or torsion bar in the driveline to absorb the ROTATIONAL pulses that are caused by the power and compression parts of one revolution of a two stroke engine.

There are two pulses to each revolution in the two stroke engine. One is the positive pulse formed when the fuel mixture fires. This pushes down on the piston and accelerates the crankshaft. This pulse last until the exhaust port opens then the crank, with the help of the flywheel, coast through the rest of the rotation until the exhaust port closes and then the second pulse begins. This is the negative pulse, the compression part of the stroke that slows the crankshaft. If the engine did not have this negative pulse it would continue to accelerate in RPM. These back and forth pulses are the ones that are causing you a lot of problems with the driveline couplings.

These pulses are very short in duration but are also strong. Even though they are using four stroke engines, these are the same pulses counted by the computer (or ECM) in the later model car and truck engines to determine when an engine is running smooth or is misfiring. (causing the check engine light to come on).

Charles

 

[LohringMiller]

The big difference between our dyno and yours is the long distance between the engine and the flywheel. In that span there are two flexible couplings and four bearings in two blocks. This means the clutch and flywheel are very well insulated from the engine. I always thought the Lovejoy coupling was overkill, but seeing your problems, I'm beginning to be glad we included it.

Lohring Miller

 

[Terry Keeley]

The big difference between our dyno and yours is the long distance between the engine and the flywheel. In that span there are two flexible couplings and four bearings in two blocks. This means the clutch and flywheel are very well insulated from the engine. I always thought the Lovejoy coupling was overkill, but seeing your problems, I'm beginning to be glad we included it.

Lohring Miller

Ya, been thinking about it some more and I may havta separate the one way bearing and the clutch instead of having it as a single unit.

Or move it down stream like you guys did.

 

[Terry Keeley]

Got the motor end supported with a big ceramic hybrid R12. Thanks again to my Consigliere for the simple solution, I was thinking of adding another pillow block.

Should get out and try it again in a couple days. Think it'll work? Or am I gonna havta soften things up?

 

[Dennis Somers]

Impressive work for sure! Think it needs a little shock absorber. I just hope the crank or case doesn't fracture as the weak link. All the best testing.

 

[Terry Keeley]

Think I got it. Very little vibration this time. Breaking in another new piston/sleeve so only went to 20K rich but so far so good.

On the second run the motor coughed as I was shutting it down and the collet came loose, I forgot to loctite it, no damage to the motor.

 

[Terry Keeley]

I got it!

Made four good runs around 22K, nothing got hot or broke and the vibs are good. Funny, I don't hear that "clanking" sound anymore. It was 95* today and that CPU cooler had no problem keeping up.

Next stop, dyno wheel...

 

[Jim Allen]

Terry,

You will be amazed at how easy tuned pipe development becomes once you have a working test stant. Keep up the effort!

Jim Allen

 

[LohringMiller]

Amen, brother Jim. I loved developing pipes on our dyno.

Lohring Miller

 

[Notter Dean]

Very Nice Terry. I have been following your thread. The fuel consumption rate is impressive.

deano

 

[Terry Keeley]

Very Nice Terry. I have been following your thread. The fuel consumption rate is impressive.

deano

Thanks buddy.

Ya, that's a 24 oz. tank so from the video it looks like about 6oz/min. at full throttle. If that .67 ci motor were 500 ci it would translate to about 0.6 gal/sec. A TF dragster burns about 1.5 gal/sec at full throttle so our little motors are similar.

I've found over the years most running problems are caused by fuel delivery issues, ie: crap in the needle, lines too small/long, pressure lines pinched, leaking exhaust system etc. etc. Any little hickup in the fuel flow can cause a lean condition and either blow the plug and/or hurt the motor.

ps: Tell that kid of you're to remember the Matrix!!!

 

[Tim Kish]

Always impressed with the projects you take on but even more impressed with your willingness to share, great stuffTerry!