Direct drive SBC

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Toobuilder

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Jan 19, 2010
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4,781
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Mojave, Ca
If you're going through the trouble of an indirect drive, might as well gear it properly to make the HP. A 1:1 drive is all the hell of a PSRU (TV, weight, inefficiency) without any of the benefits.

I'd wager that running the engine inverted ends up significantly easier and lighter than engineering a jackshaft.
 

Erik Snyman

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Joined
Oct 9, 2019
Messages
55
1. By making the engine sprocket bigger than the shaft sprocket, you will have a reduction in engine revs for any given prop blade length.
2. Make the shaft hollow, devise a way to feed engine oil into it, and you can fit a hydrolic c/s prop.
3. By lifting the thrust line of the prop, you can run a larger, more efficient propeller at reduced revs.

Erik in Oz.
 

Bill Welter

Member
Joined
Jun 10, 2019
Messages
21
A direct drive auto conversion always scares me, I keep wondering when the prop gyrations are going to finally break the crank or chew up the thrust bearing. Besides, auto engines are don't make enough power at 2700 RPM. I'd go with a redrive just to keep from breaking the crank. Folks have used airboat redrives that have spur gears in order to increase the RPM and raise the prop shaft
 

Jay Kempf

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Apr 13, 2009
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Warren, VT USA
No one saying direct drive without mods to the output end of the crank. Most have a secondary bearing assy at least. Some quill shafts. Pushrod engines are light and simple.
 
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