Tapering Axle Heads

[Gameday]

All, whenever one of you guys post a car pic I scrutinize every detail and I notice that it seems the axle heads usually retain their original convex shape.

We use the pro axle tool and after we straighten the axle we then taper the head by placing it in the guide and pounding it 4 or 5 times. As a result, the head it totally flat and is very tapered. Also, there is almost no bur left that has to be filed off.

Am I over-doing the tapering? Would I be better off gently hitting the head and then spending more time on filing a taper?

Thanks.

[PWD_addict]

I just use a file for the taper. Don't know if it matters but it's very easy to do and I think it looks better on both sides of the head!

[doct1010]

Would I be better off gently hitting the head and then spending more time on filing a taper?

Thanks.

That is the method we use. Small triangle file or needle file works well on the bevel. Careful not to score shaft, we have a very thin brass shim laid over axle to protect it during filing.

[PWD]

This is something our rules indicate is not allowed but it seems like most racers do it and are never called on it.

[derbster]

We have pretty average-to-strict rules, but there is never any inspection except

does the car weigh less than 5 oz
does it fit in a box of A x B x C inches
does it straddle a mock track (ie the 3/8" clearance)

The other rules are never checked (alter wheels, alter axles, use liquid lube, ebay cars, etc)

[Gameday]

I guess it never occurred to me that some Packs or District might have a rule against tapering the axle head. It's allowed in our Pack and District.

[PWD_addict]

This is something our rules indicate is not allowed but it seems like most racers do it and are never called on it.

PWD--you should volunteer to inspect next Derby! It's not fair if some unscrupulous boys/parents decide to break the rules because they know they won't be called on it. Even if it is difficult to inspect for. IMHO, if it is difficult or nearly impossible to inspect for, it should be allowed (within reason).

[parrot_racing]

Would reducing the circumference of the axle head elimate more friction than tapering of the head? Seems that tapering, if over done, will create a binding effect as the smallest part of the taper may slightly penetrate the wheel bore. Any physics lessons to be learned on this?

[doct1010]

Would reducing the circumference of the axle head elimate more friction than tapering of the head? Seems that tapering, if over done, will create a binding effect as the smallest part of the taper may slightly penetrate the wheel bore. Any physics lessons to be learned on this?

I'll leave the physics to those who actually know. I think the intent of the bevel is to reduce the surface area, so rather than having the entire underside of axle head contacting you reduce it to just the small band at it's base. That's the best I can do.

[parrot_racing]

Thanks doct1010, so the taper isn't so extreme that it is totally cone shaped, I guess.

[Stan Pope]

Would reducing the circumference of the axle head elimate more friction than tapering of the head? Seems that tapering, if over done, will create a binding effect as the smallest part of the taper may slightly penetrate the wheel bore. Any physics lessons to be learned on this?

Both actions can be effective to the same extent. The head diameter should not be small enough that part or all of the bore around it. The taper should not (and need not) be extreme enough to bind.

The purpose is to push the average radius of the contact patch as near the center of wheel rotation as possible so that the friction (which is pretty constant, regardless of area) is least effective.

Tapering is frequently allowed. Sufficient head diameter reduction to be useful would probably be rejected because it makes it difficult to recognize the axle as Original BSA Issue.

Grandson worked his axles this year on a lathe. Approximately 0.36" of axle shaft were affected and the shaft and head taper were addressed with the same tool in one continuous process. The process required a very light touch on a manual lathe, and I was impressed that a Bear-age Cub Scout could do 6 of them without ruining a nail AND without crashing the tool into my chuck! Of my first dozen, I ruined 2 of the axles... they climbed right up on top of the cutter! A ProAxle Press applied the the portion of the axle "point-ward of the ridges left the nail in good shape for turning! It was important to take small bites and to work from the chuck-end of the shaft out toward the nail head.

He did cone the entire underface of the nail head. But it was an exceedingly squat cone! And the junction between shaft and nail head was very "clean"... no gouges into the shaft