Adding extra keyways in banjo axles

John Kennedy

John Kennedy

Senior Member
Has it been done? If not, why not?
I was reading a thread and the broken axle key situation came up, and was thinking why not have 3 evenly spaced key slots per axle? Seems like most any machine shop could do that.

Good idea? Bad idea? :confused:
 
Is that the design then? The key is a "driveline fuse"? I'm not going drag racing, just wanting a reliable daily driver with a flathead.
My rear end is a '48 truck.
 
I would think as long as your Flathead is not too hot, and you don't drive it hard, it should be fine the way it is.
 
The real hold is the taper, not the key. When a key shears I believe that indicates tapered contact area failed to hold...causes would be low torque on nut or damaged surfaces, likely caused by running loose. I do not have torque figure here...Ford actually released one in the '46-8 period. It is VERY high, and results in a serious grip, along with serious work with proper puller when it has to come back off!
 
Tapered key ways are one of the strongest. the weak spot is when you don't tighten the axle nut enough. I believe the torque spec is in the neighborhood of 150 ft lbs. most folks give up around 70.
 
A torque spec was previously published here on the 'Barn. As a sufferer of CRS disease, I can only tell you it was North of 200 ft.lbs. REALLY tight. Locking tapers are hard to beat if done properly.
 
I weigh about 175, and have a wrench that's about a foot long... And I jump on it... I put my A-V8 together with less than perfect parts, I tightened them up a LOT when first on the road... Karl
 
Need to look this up...V8 times published a Service letter that Ford sent out around '46-48 giving what I think was the first published torque spec for this...it was 200 or a little over, then they almost immediately sent out a second letter backing off to a bit under 200. Do not have exact figures here...
At any rate, it needs to be tight, tighter than most folks would go if working without a spec. Axle ends, nut, etc. are the same exactly back to 1928, and Model T's used the samr thread size there.
 
Back in the 40's and 50's a lot of guys were using Ford rear ends in their circle track cars. They ran saftey hubs but were breaking axles at the base of the keyway.
We experimented on a stock model A first and lapped the axle to the hub to get 100% bearing surface.
Cleaned the surfaces off with acetone and assembled it dry at 150 ft lb
with a heat treated high nut and NO KEY. We drove that car like it was stolen and never had the tapers slip so we tried it on the race car with a key. We broke axles once in awhile but never had a taper slip or a keyway mushroom out.
 
My dad worked at a Ford dealership in 1932 and he told me to tighten the axle nuts as tight as you can get them and then "one more round" LOL
 
my grand father always had a spare axle set aside and let it rust up at the taper and used the key,he said it'll never slip and I do remember he tightened it up with a cheater pipe,and never had a problem, in later years I called the rust process poor mans locktite !
 
I have lapped in the axle to the hub to the point you push them on by hand and have to use the tool to pull them off, never had any trouble after that so long as you have a good keyway, then they break behind the keyway if your going hard on them.
 
The Ford Bulletin specified 200-220lbs and then a bit more to line up with the next cotter pin hole, but not to exceed 275lbs.
I did mine to 200lbs and I tell you I was scared witless I was going to snap the axle! :D
The crucial point is to lap the hub taper to the axle taper with valve lapping compound until you have a nice even dull grey finish. This ensures the taper, which as Bruce pointed out is the thing that locks it on, is getting maximum purchase. Its like the Morse taper used in serious drills and lathes.
The key is really irrelevant if all other factors are right, its only a backup system and should not be regarded as the main locating feature.
 
All good to know, thanks! I like the valve lapping idea. Guess this is best done after I get the axle located in the frame.
 
Many years ago, a very knowledgable John Deats explained to me that IF the nuts are not tight, very tight, that the taper won't hold and the the hub will
"work" on the key and over time, the keyway in the axle will spread and a crack will develop at the inner end of the keyway, and eventually the axle will
break at that location. Accordingly, the nut needs to be tight enough that the
hub cannot rotate on the axle. If one depends on the key alone to transmit the driving force, one is destined for disaster... If you don't need a (KRW) puller to remove the hub, check the keyway...

We see alot of axles with damaged threads, which causes concern that they may fully strip if alot of torque is applied to the nut, so usually they are not tight enough.
 
I talked to an old dirt tracker and they would use cut down screwdrivers as key stock because they were hardened. That's the story he told me.
 
If tightening does not scare you and removal does not terrify you, they are not tight enough. I always feel like one more touch on the puller is going to lead to high-velocity shrapnel before the thing pops!
 
I think the automobile manufacturer's back in that time frame always tried to sell service with their products and FoMoCo was no exception. If the car was serviced every 2000 miles and the tapered axles were retorqued at least that often then there would have been less problems with looseness and fretting. Most customers are not all that keen on going back to their dealer any more often than they have to so consiquently, the axle get loose & the joint has problems. The only way they could rectify that was to just torque the hell out of them to start with. No telling how long it would be till it was retorqued.

On the main rotor hub nuts for a helicopter or "Jesus nuts" as they are sometimes refered to, we retorque 25-hours after install to make sure it is reseated. Nobody forgets to retorque a Jesus nut though for some reason!

Kerby
 
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I'm sure that someone, somewhere in time has cut an extra keyway or two in an EFV8 axle. I don't think Henry would have done this because it may have added an extra operation, extra cost for time and cutters. I'm not a mechanical engineer or a metallurgist but I would also believe the addional keyway cuts would weaken the axel. JMO
 
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