Redrive Problem with the Bulldozer

jcarleto

Aluminum Supporter
Joined
Jun 5, 2007
Messages
3,571
Location
Taylorsville, GA
Aircraft
Beech Bonanza G-35 N4638D/"The Bulldozer" 2-Place Gyroplane N575EE
Total Flight Time
Several
This is a quote from another thread, but the answer belongs here:

animal said:
Did you fly the Bulldozer? how many hours do ya have on it now?

how did the new muffler system turn out?

Yes. I flew the Bulldozer to RMG last weekend. It now has 2.6 hours with the longest flight being .7 and the last flight .5 to RMG. It is now parked and apart in the PRA #56 hangar. All the flights were excellent, including the one to RMG...right up to the point that Lewis asked me, "what's that dust on the starter there." It was dust from Gates belt wear.

The muffler system worked out fine.

I have modified or rebuilt almost all of the machine from the original kit. The one thing I didn't touch was the reduction drive. I have been checking it religiously before every flight, and it had been looking fine. After landing at RMG, it was clear something had changed. The pulleys were out of line and it was wearing the belt at the edges.

My first thought was that the bearings in the prop side had failed. It uses a trailer hub and axle shaft to connect the prop hub. After a complete rebuild and fairly exhaustive examination of the prop hub assembly, it was clear that wasn't the issue...but that's now rebuilt and what is inside is solid and correct.

It took only a second of spinning the motor over to locate the real problem. The lower Gates pulley was off. The root cause is a combination of 3/8 bolts instead of 10mm securing the pulley to the crankshaft...close but not close enough....and some aluminum spacers for the ring gear that should have been made to tighter tolerances.

This is all being replaced/repaired. I'm really pretty satisfied with the trailer hub mechanism, even if it is a bit "hardware-ish." If the crankshaft Gates pulley had been stable, I wouldn't have had a problem. I didn't expect that, and should have taken it apart and checked as I did with everything else.

On a positive note, I have found a pretty good source for Gates belts. I had a very good experience with http://vbeltsupply.com in getting a replacement belt. Prices on Gates poly-chain belts are never good, but theirs was better than most and their service was excellent.

The belt I removed was only slightly damaged, but I cut it up so it could not be used by me or anyone else by accident.
 
It may have been useful if I took pictures prior to the state the machine is in at this time. Unfortunately, I was consumed by troubleshooting and repair and not photos. Once the new parts are completed, I may try to shoot some before/after shots.

*JC*
 
Wayne To The Rescue

Wayne To The Rescue

I had Wayne Stargell make me some new spacing (and now, alignment) plates for the Bulldozer after finding the problem with my re-drive.

The first picture below shows the original parts. The holes in the spacer plates are too large and there is no boss or key for alignment, and the bolts were wrong. These are 3/4" SAE 24 thread and the Subaru engine uses 10MM by 1.0 pitch bolts on the crankshaft.

The second picture shows the parts made by Wayne. Notice the stepped boss on the rear (crankshaft side) flywheel spacer. When together, everything sandwiches nicely and there is no chance of a misalignment failure as before. Wayne also trued up all the bolt holes and balanced the setup. Thanks Wayne!

I could not find a source for 10MMx1.0x150MM bolts, so I had to go with A193 B7 threaded rod. Perhaps that is why SAE bolts were substituted. They were not a good substitute.

*JC*
 

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Oops! Wrong Picture

Oops! Wrong Picture

OK...perhaps you can see the stepped boss in this shot.

*JC*
 

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Looks good Now,
That should fix it Jon,

Can't wait for more video of it flying.
 
Back In The Saddle Again!

Back In The Saddle Again!

Thanks to a lot of help from Lewis Gulley and Wayne Stargell, the new, improved Bulldozer re-drive is together and I flew a very pleasant and uneventful test flight at RMG this afternoon. It was 95 degrees F (and at least 100F on the runway) and 84% humidity. The density altitude was over 3000 feet. Still, I was able to climb out at 500 ft/minute.

The sad thing was I had to stop after only 2 laps around the pattern. It was the "right thing to do" after such a major modification. I was having a blast and the machine was humming along nicely, but I landed and dutifully taxied back to the hanger for the test flight post examination. No issues. All seems to be working well.

I guess I'll just HAVE to get out there and fly more to make sure. :D

*JC*
 
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