Prop Shaft

[78Southwind]

Interesting. I've had several say good things and several say bad things about Whip Struts.

[HotWater]

Two different style's of machines and tooling used to cut the keyway's pictured. Is one of them less prone to develop a crack at the end of the cut?

[HotWater]

I don't like either one of those slots. Both have zero fillet radius. My opinion, they should have .040 minimum fillets. But between the two, I would take the shaft cut with the endmill(bottom) less work hardening with this process. I feel the slots on the prop shafts should be cut with a ball endmill and the key should have the same full radius shape.

Thank you for the response. I've never seen key stock radiused on one side to match a ball endmill slot. Is that common stock? Can you explain to me what fillet radius is and the benefit of it?

[sangermike]

the only thing I've got to add on the whip strut is I have one on my Sanger mini both burgeon and Wilkes recommended it on that style boat

[HotWater]

You would need to make or modify the one side of the key.
See pics for fillet and no fillet.
Attachment 33610Attachment 33611

Another issue I have with cutting slots with a keyway saw is, you have a longer runout of the slot. Reducing the cross section thickness over a longer distance of the shaft. Making it weaker for a longer distance.

Got it, thanks!

[JusTrouble]

Know anyone around Fresno/Clovis that does ball endmill cuts? Im about to need that done on my Belmont when I put a shaft release on it.
Thanks for the explanation and diagrams. Now I understand what Ive been told before.

[gn7]

I don't know if I would ball mill, but I totally agree with the radius in the bottom cut Westernaero posted.
Look a square stock Craftsman screw driver and you get the idea of what the key slot should look like.

[gn7]

You use the slot you like, I'll use the one that works for me.
I have seen the full radius slots try to roll the key under a lot less force than a boat prop. Might be the kick ass set up if the key is precision fitted, and the depth is dead nuts on, but most props and shafts don't get the attention to detail that a rocker shaft is afforded. Specially in the pits of a race.

Used a radius bottom end mill, and a craftsman screwdriver shank for close to forty years and not broken a shaft yet. So I think I'll stick with it until I am making at least 2500HP. Then I'll switch to this.

[HotWater]

Don't argue with me Bob.
Look at the circled area, this is why I say ball endmill and full radius on the key. Notice the pinched pressure area, there already cranks in there, in you can bet on it.
Attachment 33792

That circled area is the end of the old slot. We cut the shaft and extended the slot. It shows that the key rolled or tilted a little in the slot. Would a ball end mill slot with matching key eliminate that or be worse?

[gn7]

That circled area is the end of the old slot. We cut the shaft and extended the slot. It shows that the key rolled or tilted a little in the slot. Would a ball end mill slot with matching key eliminate that or be worse?

Well, you may have extended the life of the shaft. Like Westernaero said, that slot has seen some stress. Being it WAS the end of the slot makes a lot more sense. Now that its in the middle of the prop, its not nearly as likely to fail there. Not say it can't, but I have never seen a shaft that didn't fail right in front of the prop.