Drive Train Horsepower Capacity

PostPost by: rodney » Thu Aug 19, 1999 10:53 pm

At 12:03 PM 8/19/99 -0500, you wrote:


Tom

The Elan sprint was supposed to have 130 HP and the only modification was
beefed up donuts. Most people have replaced their original donuts with the
sprint ones as they give better service.


Rodney Stevens
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PostPost by: rodbean » Thu Aug 19, 1999 11:48 pm

"SMITH, THOMAS B. (JSC-SP)" wrote:


I wouldn't go more than about 150 hp with donuts, even the Sprint donuts in
common use now. Aside from the donuts, the weak links are the stub axles.
Either the original ones should be removed and heat treated (they are 4340
steel) or new replacement competition stub axles from Tony Thompson, Dave Bean,
etc. should be installed.

Both the inside and outside stub axles should at least be heat treated if a lot
of horsepower is planned (assuming sticky rubber too). The insides go first
and are generally considered the weaker of the two types but I've seen outside
stub axles break too and the driver was very lucky both times. Both times it
was the same car (opposite sides) and in fast turns on race courses (Riverside
and Pomona). When that happens, the wheel comes off! It has the potential for
disaster but fortunately wasn't in these cases.

The integrity of the outside stub axles can be helped quite a bit by doing some
judicious grinding at the ends of the keyways. They fail just where the keys
ends and this area can be relieved and smoothed (see tech manuals from Golden
Gate Lotus Club, Lotus West, Lotus Ltd. and Dave Bean's catalog.. etc. for
instructions).

With the good stub axles and CV or universal (Spicer-type) joints, everything
might be good for about 275-290 horsepower. I'd start getting nervous after
that.

Rod






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PostPost by: ozone.breath » Fri Aug 20, 1999 1:23 am

Tom Smith asked:

Rod Bean commented:

<much additional, interesting detail about stub axles snipped>

Yeah, Rod, I seem to remember Fred McClung saying somethin' about
the original stub axles being UN-heat-treated 4340... which seems
pretty surprising, eh? Based on Caroll Smith's wisdom, UN-heat-
treated 4340 isn't really much stronger than mild steel. Getting
the stub axles heat treated properly would seem a very effective
tweak, and might be a lot cheaper than ordering new ones... but
get them crack checked first. No point in heat treating cracked
stub axles!

What material is being used for the modern, unbrako stub axles?
Anyone know?


I agree. In fact horsepower probably isn't even the main issue!
In low gears, tire adhesion is a safety valve that would preclude
loading the rear "axle" to anywhere near that torque level.

Even in top gear, with the distinct possibility of putting Moby
horsepower on the ground, the differential and rear suspension will
have less than the maximum (tire adhesion limited) torque loading
that would be attainable from a standing start.

I would be more worried about the kinds of things that cause impact
and cyclical loading on the differential and the stub axles. Clutch
engagement, for example. Tires significantly out of balance, which
is probably more likely to happen on a race car, and which is probably
about 4X more worrisome at 120MPH than at 60MPH. Driving styles are
obviously a key factor too.

What about the gearbox? Stock gearboxes have been known to have
significant reliability problems on racing Elans... but is this
because of high input shaft RPM, or plain old torque loading, or
something else? Anyone know?

Regards,
Erik Berg






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PostPost by: "SMITH, THOMAS B. (J » Fri Aug 20, 1999 3:27 am

Thanks Rodney. How can I tell if I have the beefed up donuts?

Tom






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PostPost by: types26/36 » Fri Aug 20, 1999 3:34 am

The last of the breed, the (non-Federal) Elan Sprint and Plus 2S 130 had
about 130 bhp. They had the stiffer rotoflexes as others mentioned, and a
very important reinforcing bar across the top of the diff upper mount lugs.

Randall





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PostPost by: rodbean » Fri Aug 20, 1999 11:31 am

"Erik V. Berg" wrote:


Well since Fred was the driver when the wheels came off, he ought to know. Just
so everyone knows, this was a slalom car with a Hewland cam and pawl limited
slip, about 130 hp and race tires on 6" wide magnesium Minilites. The driveline
components saw a lot of shock loads as both Fred and I drove his car in every
slalom we could all year.

The stub axle failures occurred on race courses because we had started to run
Solo I events on open road courses. Actually, we had at least one inboard stub
axle break on a slalom course too.

Fred's was the fastest car of many Elans running slaloms at the time. The fix of
replacement stub axles for competition was not available then so I'd guess that
we were among the first to find the limits of those components. These days,
Elans are in demand for vintage racing as well as slaloming and these needs have
been addressed by Tony Thompson and others.


I have heard stories about limitations of the Ford gearbox but I haven't seen
it. I'm sure there are limits but, as you've implied Erik, the tire adhesion
would probably be the safety valve.

John Clark's slalom car would be a good example of both stub axle and gearbox
durability. He had 10" wide Revolution wheels with comparable race tires and
huge flares to accommodate. The car had about 175 horsepower and received
regular use of many many runs at many many practice slaloms (unlimited runs) as
well as championships (three runs) and also some Solo Is.

Chris O'Donnell's Elan has a 2xx hp BD engine and is used exclusively for
slaloming.... also large flares and race tires on wide wheels. Chris' driving
style is perhaps the most violent I have seen and the car takes it.

Rod






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PostPost by: markvo at home.com » Sat Aug 21, 1999 3:24 am

The sprint also got a stiffening angle bracket which mounted between the
differential housing upper arms (Al) and the chassis and was also bolted
to the uppermost bolt of the same housing and differential nose piece by
way of a small sleeve welded to the bracken. This required a longer
replacement bolt to pass through the sleeve, then through the nosepiece
nd into the aluminum housing. This bracket helped stiffened the
aluminum differential housing and keep it from twisted as much under
torque.

I am restoring an Elan with well over the sprint's 126 hp. and have read
about differential output shafts along with the outer shaft that runs
through the hub being twisted by modified engines.

What is the most ecinomical way to upgrade the entire rear-end,
especially the mentioned shafts. I would also probably like to use
u-joints or cv-joints as well.

Mark VanOsdel

Rodney Stevens wrote:






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PostPost by: abstamaria » Sat Aug 21, 1999 1:26 pm

Hello Mark,

You might want to look at the "Glide-coated" sliding-spline set that Tony
Thompson sells. This is not quite the ball-bearing spline set that the 26R
used, but is at least similar in principle of operation. It looks like the
original item and should be acceptable to most vintage racing bodies,
including the FIA. If this is not a concern, of course CV joints are the
way to go.

TT also has inner and outer billet steel output shafts, but these are not
inexpensive. If you want lighter weight, he has aluminum diff nose pieces
as well in the correct shape (as well as magnesium back covers).

Regards,

Andres
45/8439








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PostPost by: "SMITH, THOMAS B. (J » Mon Aug 23, 1999 1:58 pm

Just wanted to thank everyone for the excellent information provided on the
Elan horsepower question (rear end). Great stuff...I can't wait to put it
to use!

Tom





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PostPost by: davidcroft » Thu Sep 02, 1999 8:55 am

Thanks to everyone with all your tips about my little timing chain
noise.

Too many good ideas to respond to every one individually, but I will be
trying out all your thoughts.

This list is great isn't it? As a real novice, your collective responses
stop me from getting discouraged.

I was expecting the car to need a lot of attention, but maybe not this
much.

The overwhelming impression I get from the list is that no problem can't
be fixed, and that I'm not unduly unlucky with my car's faults - and
above all I've joined a great bunch of real enthuiasts.

To the non-lotus owning listers - buy one.

Thanks again


David






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