Wooden props and Belleville washers

SMOF

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My new/old Bensen has a wooden prop on a Revmaster 2100-D engine.

What it DOESN'T have are Belleville washers.

Another thing I discovered that it has is a little charring on the hub-plate side of the prop. Gee, I wonder how THAT could have happened???

I recall from back when I was young (and dinosaurs ruled the Earth) that the plans set included a sheet showing the entire engine engine and prop mounted -- including a sketch and note about Belleville washers. However, looking at what I got from the former owner, I don't have that sheet (the "power conversion" sheets I have are 1 and 3).

Could someone please check their plan set and let me know A), how many Belleville washers are supposed to be there (6 per bolt?) and B), any specs given for them?

I've got a Warp Drive that I could put on this, but really, the wooden prop has CHARACTER . . .I'd just as soon keep it.
 

gyrojake

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They are not a necessity but here is an example.
This is an installation on the Cozy airplane.
 

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Chris Burgess

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My books show 4 per bolt for a total of 24 needed. Only number is the Bensen number, 1000-50, 24ea, 1/2 ID, Belleville Spring Washers. They are stacked in pairs cupped to each other. These would show "light" between them indicating a "shrinking" wooden propeller and a re-torque being in order. That "charring" you say you have is a sign the bolts needed to be re-torqued.
 

eddie

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i have seen wood props actually catch fire from the friction when loose.




Best regards,
 

SMOF

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Thanks, everyone!

Yes, I know about how Bellevilles work, from before, and about hub charring. That's why I want to get them, but needed to know how many to get. Gonna have to get new prop bolts, too, for the added length.

The former owner had castle nuts with cotter pins, and a skullcap spinner over the hub bolts. I'm going to skip the skullcap, so I can see the bolts.

Hmmm . . .looking at the link that Jeff posted, I see various thicknesses of washer. Anyone have a guess which I want?
 

bryancobb

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Thanks, everyone!

Yes, I know about how Bellevilles work, from before, and about hub charring. That's why I want to get them, but needed to know how many to get. Gonna have to get new prop bolts, too, for the added length.

The former owner had castle nuts with cotter pins, and a skullcap spinner over the hub bolts. I'm going to skip the skullcap, so I can see the bolts.

Hmmm . . .looking at the link that Jeff posted, I see various thicknesses of washer. Anyone have a guess which I want?

Start from the proper torque for the bolt size used. Determine the tension in the shank that creates. Then use enqineerinq data on Bellville washers to determine stack confiquration to create that amount of tension.

The coefficient of expansion of the type wood used (from prop mfq.) is a factor in determininq how many washers to use.

Stackinq them and measurinq how much force it takes to compress the stack is a qood way too.
 

gyrojake

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I've flown my V.W. for 600 hours with a wooden prop and only used a crush plate and no Bellville washers.
I never had a problem with the prop coming loose or charing the wood.
 

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SMOF

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Jake, I love your tail art.

Mine has a Revmaster on it. Crush plate, no washers, moderate charring of the varnish on a B&J prop.
 

SMOF

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Start from the proper torque for the bolt size used. Determine the tension in the shank that creates. Then use enqineerinq data on Bellville washers to determine stack confiquration to create that amount of tension.

The coefficient of expansion of the type wood used (from prop mfq.) is a factor in determininq how many washers to use.

Stackinq them and measurinq how much force it takes to compress the stack is a qood way too.

Dr Igor already worked all that out for the Mac with a wooden prop that is pretty much the same size as the VW with a wooden prop. I figure that doing the same thing now that we were doing back then should work, I just don't remember the thickness or configuration.
 

HobbyCAD

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How we do it, is we have an external cup over the belleville washers. When tightened up to the correct crush, the space between the cup and end cap is 0.8mm. During inspections, we use a U-shaped feeler gauge of 0.8mm thick to check the gap. If the gap increases, the crush is diminishing due to either the bolt loosening or the wood shrinking. This method is a quick and easy way to ensure your wooden prop remains correctly installed.
 

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SMOF

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Is that from the Bensen sheets? I don't remember using cups, but I like that idea a lot.

Where are you getting the cup and cap? Do you have part numbers for anything?
 

HobbyCAD

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Is that from the Bensen sheets? I don't remember using cups, but I like that idea a lot.

Where are you getting the cup and cap? Do you have part numbers for anything?

SMOF, it's not from a Bensen. We make them for our Seabird Seeker's wooden pusher props.

Cheers,

Francois
 

mgk

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A PDF copy of "8-109-100 - Sheet No. 3, Power Conversion Model B-8" is attached. Hope it helps.
 

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eddie

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I never have used the washers,just a crush plate. Check the torque once in a while and at

inspection time.






Best regards,
 

Roundwing

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I've flown my V.W. for 600 hours with a wooden prop and only used a crush plate and no Bellville washers.
I never had a problem with the prop coming loose or charing the wood.

Jake,

I cannot tell from the picture but what do you use for a carb on your VW?

Single?

Dual?

Thanks,

Rick
 
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