I am in the midst of a few minor changes to the Beast, after the last crash i revamped the frame
and made a few necessary adjustments. At the race last June at Bedford, In. i broke an axle
and a CV. The Cv has been replaced, and i am in the designing stage of axle repairs. The axles
are too long and need shortening. With the old 600 and 80+ HP they worked great ,,,,,,, now
with 154 HP, they don't hold up so well. I have broken 3 welds so far. The only thing that i have
done so far is to sleeve them and reweld. Jan did a slot and "matching extension" welded fit, with
a sleeve. To save on parts, i am looking at doing a slot in both axle halves, and welding a 1/2"
wide shim inbetween them, and them sleeve.
I am still running a bit rich and still am in need of a Power commander IIIR, to adjust my mixture
The radiator is running hot, water temp is staying above 225 degrees. I am working on a "roof"
and ram air design to get more air flow towards the radiator. A trial setup, brought my temps
down to 210 degrees, Better, but no medals ,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,, tom

Tom, there is a guy near me that has built several buggies. On his most recent, and most highly developed and refined, he is running a Yamaha R1, he says that no matter what they try, it runs in the 220 range. I suspect that the greater weight and rolling resistance compared to a street bike is causing the Engine to work harder, and thus hotter.

Years ago I was talking to Bob Briggs the guy that built the Briggsbuilt stadium lites
he said the axles should be design to twist and flex becuase that is what they are
trying to do every time your on the gas or breaks, I don't think I would expect
the welds to hold up on your axle if it is twisting and flexing as he indicated, perhaps
a post weld heat treatment would help? He also said the axles he was using was from
swa-a-way and they were actually torsion bars with the corect splines on the ends
guess the spring steel of the torsion bars made them better?

Post that picture of your tire and rim again or send it by email I resized the pics and
messed that one up, sorry...

Shifter, first I’m sorry to hear about your Dad. Your comments about getting to spend some time with him recently remind me that I need to do the same.

I have debated whether I should comment on your axle situation. The bottom line is this is the type of part that falls on my desk so I know something. There is not much I can help you with at this point but I thought I would say something for the benefit of others who may be contemplating building a car. Please don’t take any of this as a criticism, just a suggestion for next time.

First off axles are high stress things that tend to be more complex than they seam. Most people assume the strength for an axle is decided by the max power of the motor (( Internal Combustion Engine ? )). However this is only indirectly true. The max torque event is more likely landing a jump. When you land one wheel hits first and tries to accelerate the other wheel instantly. If you jammed on the brakes to level the nose out mid air this can put a lot of stress in the rear drive line.

Second thing is that the half shafts of a car are a well engineered unit (at least I hope they are). The strength of the CV’s and the axle are matched. If the CV is strong enough for you application then the axle should be about the same strength.

So my recommendation would be to use the half shaft as a unit with out alteration, if possible. This takes measuring axles to find something close to what you want then fabricating around them. VW water cooled cars and Audi’s from the late ’70 to mid ’90 are good candidates. Also if you use air cooled VW parts there are many axles intended for off road buggies that should work. The air cooled VW parts are well known in off road circles and there is a lot of information on the web. ATV’s also have neat half shafts but they tend to be short and expensive.

Axles tend to be very notch sensitive. I would imagine that they do not like welds. You could try grinding the welds but the difference in heat treat and the different weld material will still cause a stress riser in the axle. If you stress relive the axle (heat it up red hot and let it cool slowly) it may improve the situation but most axles are heat treated to improve there strength (I have heard that the water cooled VWs did not heat treat there axle but I don’t know this for a fact).

I do have experience with modified CVs. A new stub shaft was put on by cutting off the cup but leaving the base on the stub. The new cup was welded on but the weld was at the OD of the CV cup. So the weld length was much longer than if we just welded on a new stub. This reduces the stress at the weld. The part was stress relived, the weld ground off and then the part was re heat treated but this is not practical for home application. I guess what I am trying to say is that do every thing you can but don’t expect perfection if you can’t do it all.

Well, this has gotten a little long winded. The bottom line is that you want the axle to be as strong as practical for a home built (barn job) buggy.

Here are a few pics of the Fox alterations,,,,,,,,,, 4" spacers, new shafts, new valving