[Fot] TR4 axle shafts

[John Styduhar]

My "copycat" Southwick conversion on a TR3 rear axle uses the 9" small Ford
housing ends (the housing ID for the sealed bearing is 2.835").  The last
step on the housing end is removed and then fit perfectly over the axle
tube (2.25"OD) for welding.  The Ford axle housing fits right up against
the small locating tab which located the outer leaf spring u-bolt, so
orientation for track width is easy.  Moser engineering sells the 24-spline
axles for $370.00, bearings and wedding band retainers installed for
$75.00, and they can drill the stud holes on a 4x4.5 pattern for whatever
wheel stud knurl diameter you are using.  Make sure to have them drill an
access hole in the flange to make it easy to install and remove the axle
without taking the brakes apart.  Same setup for TR4 but longer axles as
you TR4 guys and gals already know.  Like Tony mentioned, the brake backing
plates will need to be modified for the 4-bolt bearing retainer (backing
plate ID needs to be enlarged slightly to slip over the bearing and the 4
mounting holes for the C-shaped retainer need to be drilled).  As another
patron mentioned, you can mock everything up and do your welding in situ.
While your welding, go ahead and weld the axle tubes to the pumpkin for
stiffening.


On Sun, Jan 19, 2014 at 8:54 PM, Tony Drews <tony at tonydrews.com> wrote:

> The stock design solid axle will flex in the tapered portion where the hub
> is pressed on.  The car I rolled had stock design axles but made out of
> very good steel and stock design hubs also made out of very good steel.
>  They were manufactured so that the "stress risers" were removed, but under
> load the axle, about 1/3 of the way inboard of the outer nut, starts to
> flex.  You can see the fretting inside the hub where that happens.  It
> bends over and over until it breaks.
>
> The "Southwick Rear Axle Conversion" uses Ford 8" axles that are cut down
> in length and re-splined for the TR-differential.  The outer end of the
> axle tube is cut off and the outboard end of a Ford 8" axle tube is welded
> on.  It is possible that someone sells just that outer end of the axle
> tube.  The backing plates are machined in the center to have a larger
> diameter hole and holes are drilled for the 4 bolts which hold the axle
> bearing into the housing.
>
> These axles are a one piece design - the hub / flange is part of the axle
> shaft.  The outer bearing is pressed on and an inner retainer is pressed on
> to hold the bearing in place.  It is a sealed bearing, so acts as the
> bearing AND the outer seal.  There is an o-ring which goes around the
> outside of the bearing to seal that area too.
>
> Those axles don't normally break.  Stock Car racers bounce them off of
> concrete walls and just bend them.  And, if they DO break, they break
> between the outer bearing and the differential so that the wheel stays on
> the car.
>
> I'm describing all of this so that it may help you or give you ideas.  It
> would be good for someone in Europe to do a similar axle conversion for the
> Triumphs.  I get occasional messages from someone overseas wondering how
> they can have that conversion done.  Right now it involves sending an axle
> housing to Southwick Machine and Design and having them send it back.
>  That's expensive in the US and TOO expensive for someone not in the US to
> do.
>
> We came to the conclusion that any design with a separate axle and hub
> comes with the possibility of having the hub and wheel separate from the
> car.  I'm sure that with beefy enough parts of a good design that this
> problem can be overcome though.
>
> Tony Drews
>
>
> At 04:29 PM 1/19/2014, MadMarx wrote:
>
>> To get more knowledge about the TR4 axle this weekend I did the
>> engineering
>> calculations about the axle shafts in search to solve the question:
>>
>> Why do they break?
>>
>> I found out that on a stock TR4 the axles don't meet the safety margin
>> required by German design rules.
>>
>> You need a safety margin on 1.5 and the axle with everything stock meets
>> only 1.32 which might count off some miles of that axle on heavy road use
>> or
>> trackdays.
>>
>> On a race car it gets worse. My TR4 can do 1.5Gs on low speed corners.
>> That
>> is  quite a lot more than for a road car.
>>
>> The safety maring should be at  a factor of 1.5.
>> On my racer it is 0.9 which means the axle WILL break! You need 1.0 to be
>> just on the edge with break from overload.
>> So the axle has very good reason to let go and the stock material must be
>> excellent to withstand racing for a while.
>>
>> I calculated with 42CrMo4 which is a superior steel for axles, the 2nd
>> best
>> available in ancient times.
>>
>> So the way to go for me is with an new design that fits plug and play into
>> the stock housings.
>>
>> I will take the TR2 shaft design as rough pattern but a lot stronger for
>> racing purpose.
>>
>> I tell you if I will be successful.
>>
>> Cheers
>> Chris
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