Hi, Dave Bean used to have such a device available commercially but no longer
offer it, however, I have come up with a similar device which is easy to
fabricate. I have made one set for a Titan Formula B car and am ready to make
two for a sports racer. I will try to describe my technique in words although
a drawing would be easier.
There are two parts: like a hip joint, there is a ball and a socket; I put the
ball on the end of the half shaft and the socket on the diff side--both ball
and socket end up being inside the center of the rubber doughtnut.
The ball stands proud of the end of the half-shaft. It is mounted on a rod
which extends from the half-shaft into the center of the doughnut i.e about 1
1/4 in long. I used 9/16 drill rod for this mount and a ball which was 7/8 "
OD and 1/2" ID. Each end of the rod was turned to 1/2 in. In this way, each
end had a shoulder--on the outer end to locate the ball which was held onto
the rodby a circlip and on the inner end to go into a 1/2 hole drilled in the
center of the half-shaft three armed end. I did this operation (drilled the
hole) prior to assembling the half-shaft but I imagine it could still be done
in a half-shaft which is already welded together. Once everything checked
out, the rod was welded into the hole in the end of the half-shaft. The ball,
of course, was free to turn, but I don't think this is necessary.
For the socket, I made a triangular piece of metal with holes in the three
corners to interface with every other hole in the rubber doughnut. In the
center of this triangle, I welded a piece of tubing about 1.25 in long which
had an ID of about 1 in. This was mounted on top of the three eared axle
coming out of the diff so that the tube ended up inside the doughnut.
Note in my design, the ball is not used for locating the center of the half
shaft within the rotoflex joint. Its sole function is to be a failsafe device
to hold the shaft in in its normal position until the car can be stopped after
the rubber doughnut has broken. That is why I use a 7/8 ball in a 1 in.
hole--there is no attempt at precision. If indeed you did want to use the
device both for this purpose and for centering the shaft, then you would
require much more precision and the location of the ball would be much more
critical.
Hope this helps.
Dick Buckingham, Jr.
Brian Evans wrote:
> Does anybody have a source for the little gizmo's that can be set inside of
> the rotoflex joint on the drive shaft of small formula cars? I think they
> are a pin that attaches to the axle, and a bearing of some sort that
> attaches to the drive flange on the hewland, such that if the rotoflex
> disintegrates, the drive shaft is prevented from flailing.
>
> Thanks, Brian
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