Gearbox Maintenance

[Av8r3400]

I've been wanting to change the gear ratio in my gearbox from the 80 hp 2.27:1 to the 100 hp 2.43:1 in order to get a little more crankshaft RPM. Last Sunday I had the opportunity to finally do this.

I got a gear set from Hal Stockman and a slipper clutch from a parts engine a member of my EAA chapter had, so I proceeded to take the gearbox apart to re-shim it and change the ratio.


I found a little more than I was expecting...

[Av8r3400]

Photos of my surprise...

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The back of my prop had a "dry check" -- term used by Lonnie Prince, that make me a little concerned. I sent the prop back to Ohio for repair and they tell me it will be fine. It is from the wood core drying along the grain line.


Then, after getting it all apart I discover this damage to the prop shaft!

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Luckily I have the prop shaft from the parts engine. But I am now replacing the bearings and seals as long as I have it this far apart.

I have not had a prop strike or any other impact or vibration on this engine. All that I can think of is it was from an incident by the previous owner. The paperwork had a GSC prop listed but the plane had an IVO on it when I got it...

[efwd]

What kind of Cliff Hanger is that?. what did you find?:)

Oh, just needed to wait 1 more min.

[Av8r3400]

I needed to add photos from my phone... :D

[efwd]

wow, if you weren't a tinkerer Larry, this could have ended up with you landing off field sometime soon. Glad you found that and that scenario was averted.
Eddie

[Dave S]

Larry,

just out of curiosity, any idea how much time the engine with the damaged shaft had on it; or, if it had the rotax recommended mid time overhaul?

[Av8r3400]

The engine has about 350 TT on it. I was going to do the gearbox re-shim when I was assembling the plane but ran out of time. That was another reason for doing this now, I wanted to get that "mid time maintenance" done.

[Av8r_Sed]

It isn't because of all that extra HP you're carrying around from the Zipper?

-- Just me being jealous of the stupendous climb rate you get.

[avidflyer]

It isn't because of all that extra HP you're carrying around from the Zipper?

-- Just me being jealous of the stupendous climb rate you get.

How about that huge prop as well?? Maybe I'm just being jealous as well. :-) Maybe it doesn't put any more pressure on the gearbox than a heavy 3 blade Warp drive??? Hope you get it sorted out and back in the air soon. JImChuk

[Av8r3400]

I was worried about that during the build so I did the MOI test. The whole hang the prop from a string and swing it back and forth, deal.

My calculations showed something like 4900 cubic meters per lunar rotation or what ever the units are. 6000 is allowable.

Now the 400hp, plus nitrous mega-zipper 912 has nothing to do with it... :cool:

[TJay]

Well I hope you get it all fixed up. I do enjoy those Wisconsin videos.

[Av8r3400]

Update.

My gearbox parts (nose bearing and seals) have come in. I'm hoping to assemble the gearbox back together this weekend. If it works out I may try and video the assembly and shimming process for YouTube.

My prop is at the factory in Ohio, I have spoken with Lonnie Prince and they are routing out the crack for a new piece of wood and refinishing it. I have learned that he would like the back face of the prop, where the wood is exposed, to be re-sealed (varnish, urethane or similar) on an annual basis. That would have been nice to know from the start...

[DesertFox4]

Larry, it would be nice to see that process. I've had the gearbox on my model 4 done twice in 900+ hours but never saw what all was involved.

Good luck on the re-assembly. Hope she runs smooth again.

[little rocket]

I also would love to see a video of your reassembly of your gear box and the shimming process.
Good Luck

[Av8r3400]

Gearbox is assembled and video has been taken. I have not looked at the raw footage yet or started to edit. Hope to this week.

Tomorrow I need to order a bearing for the engine side of the prop shaft so more video of that assembly to come. Then put the whole works together. Hopefully my prop will show up, too...

Maybe I'll be able to fly this thing again before Oshkosh... :(

[little rocket]

I appreciate you taking the time to video the process and share it with us so that guys like me can learn from your experience.
THANKS Dale