Wanted: 2.25" prop flange extension

[Yamma-Fox 403]

Looking for a 2.25 or 2.5" extension for my C box (75mm circle - 6 bolt).

Anyone have one on a shelf collecting dust?

If not then any recommendations that wont break the bank?

Thanks.

[1avidflyer 1983]

Are you not going to clear the cowl with the prop?  Some how the idea of an extension bothers me as I would imagine they exaggerate any imperfections that exist.  I know they are used at times, and I have no hard evidence for not using one, just my gut feeling.  How hard to shorten up the cowl if that's the problem?  JImChuk

[Yamma-Fox 403]

Yep need it to get the prop clear of the cowl.  Cowl has to go that far forward in this case for a couple other reasons.

[1avidflyer 1983]

Just googled it and found this one.  Made for a 912 to 75 MM, but it may give you some ideas.  I would imagine one could be turned down on a lathe fairly easy, as long as you could get the bolts all drilled through exactly right without any creep to the side.  JImChuk

 

flymicro.alphaoutdoors.co.nz/for-sale/rotax-prop-extension-spacer/

 

[Cloud Dancer 69]

I'd suggest you buy it. I don't think your going to get one any cheaper. You can't buy the material to make one any cheaper. If you got a chunk of metal the right size then making one might be an option. I've got a lathe and a mill and for $90 bucks I'd buy it before killing a half a day to round up the tooling and make it myself.

Here's a link to material prices. https://www.grainger.com/category/raw-materials/aluminum/aluminum-rod-stock

You going to pay more for the material alone if your trying to make it.

[Yamma-Fox 403]

Totally agree.  That perticular one goes from the 75mm to the 912 pattern  (4"?) So I have to see how Id manage that but since my propeller has both patterns I think I'll get it to work but I'd need some bushings for those large holes on that spacer Jim found.

[1avidflyer 1983]

That spacer is in New Zealand.  As far as it goes, I would think you could drill the 75 MM set of holes all the way through, and bolt it onto your prop flange.  Probably machine the extra larger ring off, but maybe just leave it as is.  JImChuk 

PS  now that I copied the picture, I see the center is meant to fit on a larger boss then the 1" boss on a C gearbox.  Probably the bottom side of the spacer has that same size boss, like on a 912.  It's about 1 3/4".  Using a prop that is made for the 912 would take care of the outside, maybe have to machine a ring that goes from the 1" boss on the gear box to the 1 3/4" hole that was meant to fit over the 912 boss.  Just to confuse it a bit more, real early 912s had a boss that is smaller than the later (after about 1993) 912 engines.

Edited 1 May 2019 by 1avidflyer

[TJay 1041]

Is it not possible to just chop a few inches off the back of the cowl Then re glass the to fit the windshield?  It doesn't take long at all.

[Yamma-Fox 403]

Is it not possible to just chop a few inches off the back of the cowl Then re glass the to fit the windshield?  It doesn't take long at all.

Unfortunately no in this case because of the airbox and oil tank which would really interfere if I moved the cowl back because of the cowl taper to the nose.  Keeping  the cowl forward to the windshield flare that is on it gives just enough room for those to snugly fit.

 

 

Edited 1 May 2019 by Yamma-Fox

[Yamma-Fox 403]

That spacer is in New Zealand.  As far as it goes, I would think you could drill the 75 MM set of holes all the way through, and bolt it onto your prop flange.  Probably machine the extra larger ring off, but maybe just leave it as is.  JImChuk 

PS  now that I copied the picture, I see the center is meant to fit on a larger boss then the 1" boss on a C gearbox.  Probably the bottom side of the spacer has that same size boss, like on a 912.  It's about 1 3/4".  Using a prop that is made for the 912 would take care of the outside, maybe have to machine a ring that goes from the 1" boss on the gear box to the 1 3/4" hole that was meant to fit over the 912 boss.  Just to confuse it a bit more, real early 912s had a boss that is smaller than the later (after about 1993) 912 engines.

Yeah the only idea I had here was to mill off the center hole "lip" seen on the top in this pic.

then mount it backwards  with the 75mm side on the c gearbox and the 4" side on the prop.

Doing it that way would require bushing inserts in the larger holes on the prop and the spacer in the picture.  Those bushings must be a standard part of 912 prop mounting?

Below is pics of outer side of my prop hub.  The wider hole pattern has larger diam holes on the inside part of the hub, kinda like on that spacer.

Edited 1 May 2019 by Yamma-Fox

[1avidflyer 1983]

Not able to see the picture that you posted.  Is it a C gear box?  JImChuk

PS  here is a picture of my early 912.  It has the smaller boss on the prop flange that I mentioned.  You can see the prop bushings there.  C box also.

Edited 1 May 2019 by 1avidflyer

[Yamma-Fox 403]

Yep this is a luga prop on the yamaha with c-box.

I think I'll see if he will sell that spacer.  With some bushings I think I'll get it to work.

Jim thanks for the find.  I missed it on my Google"ing"

[1avidflyer 1983]

Yes, one way or the other, I think you could get it to work with this spacer.  What does the back of your prop hub look like?  Does it have a larger 1 3/4" or smaller 1" hole  to fit on the prop flange boss?  JImChuk

[Yamma-Fox 403]

I am away from it right now. But it has a larger Center hole, and then the holes on the Outer Circle are larger to except the bushings.

[1avidflyer 1983]

There is a Wood Comp propeller on barnstormers with a 4.25" long extention on it for a real low price.  I would be tempted to say you take the extention for $100 and I'll take the rest of the stuff.  Not sure what shape the prop is in though, cause it's a pretty cheap price, and they don't go cheap when they are new.  JImChuk

[Yamma-Fox 403]

There is a Wood Comp propeller on barnstormers with a 4.25" long extention on it for a real low price.  I would be tempted to say you take the extention for $100 and I'll take the rest of the stuff.  Not sure what shape the prop is in though, cause it's a pretty cheap price, and they don't go cheap when they are new.  JImChuk

I checked on that one in New Zealand and he had sold it (forgot to pull the ad).

And yeah I'll want to be in the 2.25 or 2.5" length so I should probably just drop $250 for a new one the right length with 75mm on both sides. 

Mostly I thought I'd post it up here in case someone had one collecting dust and would rather have $100 collecting dust.  

Jim, hope to be flying this summer and look forward to joining your wing somewhere soon!