Lotus Elan

Elan 26r

PostPost by: boxer » Sun Apr 03, 2005 6:40 am

Am building a replacement gearbox for a circuit elan.
Using a mag bellhousing,tailcasing & a billet gearlever is a well trodden & trouble free path so i am happy to go that route.
My concerns are with the gearcasing-should I use the cast iron casing which is
tough,stiff but heavy,the weight is ,though,relatively central & low down.
Should I use a magnesium casing which is the lightest,but can suffer torsional distortion beyond 170 b.h.p leading to power loss & reduced reliability/rebuild frequency.

Which leaves the aluminium casing. Is this the best ???

Has anyone run all three & if so what are your experiences?

Thank you in anticipation B)
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PostPost by: garyeanderson » Sun Apr 03, 2005 11:02 am

I have a light weight S2 (just a stripped out, non factory Elan - 1280 Lbs.) that had Ali Bell, Gear case, tails haft and diff nose. My biggest problem was putting power down. It always seemed to accelerate harder with a passenger in the Elan. At the moment I have the Elan apart. I have replaced the ali cased 3.9 diff with Quaife limited slip with an iron case open 3.55. The gearbox will switch from an ultra close (2.51 first) with all ali case parts to a semi-close cast iron gear case and tail shaft housing, the ali bell housing will remain. This is just to get the 30 or so pounds back on the rear of the light end of the Elan. If I were to do it again (this mean buying the parts), I would go with the magnesium bell and gear case and use a Iron tail shaft housing and diff nose with some kind of limited slip (quaife, tranX, etc). It is difficult to remove weight off the front of the Elan, the only thing left of any heft are the vacuum operated headlights. This is a street driven car so I have a kit to replace them but haven?t gotten around to this yet. I would guess that would remove an additional 15 Lbs.
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PostPost by: steveww » Sun Apr 03, 2005 8:14 pm

You could loose weight off the front with an ally block from Burton if the rules allow it ;)
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PostPost by: rgh0 » Mon Apr 04, 2005 9:59 am

Biggest challenges with a 170hp plus engine is stopping shedding gear teeth off the standard gears and stopping the layshaft spinning in the casing. New quaiffe straight cut gears stops the first problem. Stopping the layshaft spinning requires a tighter fit than standard and blue printed assembly of the box with a specially manufactured layshaft to achieve the right press fit. TT in his alloy cases uses a bronze bush to locate the layshaft to ensure a tight enough fit can be achieved compared to mounting the layshaft direct in the relatively soft alloy.

I have only run the Iron case as local racing rules dont allow the lightweight components. I have enough trouble stopping the layshaft spining in the iron case the alloy cases can only be worse given the greater thermal expansion of the alloy and/or bronze. The Elan Factory in Australia has developed a layshaft with an additional locating pin also to help prevent the shaft working loose, fretting and then spinning

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PostPost by: twincamman » Thu Apr 14, 2005 12:56 am

then again pushing AWAY from the table earlier could save 30 pounds --and save large dollars ------ 230 lb ed :lol:
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PostPost by: rgh0 » Thu Apr 14, 2005 12:03 pm

Gary

Why did you replace the Quaiffe LSD centre with an open centre in your diff changes if you are trying to ensure you get the power down? The Quaiffe centre fits the standard diff components and in my experience very beneficial for traction especially off the line and out of slow corners.

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PostPost by: garyeanderson » Thu Apr 14, 2005 1:47 pm

Hi Rohan
The basic fact is I was just to lazy to tear down both diffs and swap the quaife with the open diff. I also plan on using the Ali gearcase, tailshaft, and 3.9 diff with the quaife in my Lotus Cortina project where the reduced weight will be more bennificial. I got the S2 Elan running on Monday, I was able to get in a short ride and as I shifted through all 4 speeds the change was basicly un-noticable until I shifted into 4th. I live on a street that is a 40 mph zone that changes to 45 mph, normally I put it in 4th and its quite comfortable, this time I felt like I was geared too high (which is what I wanted). I haven't had it on the highway yet but I feel that I may be able to drive more than an hour at a time and enjoy it. I may yet get the headlights with the associated vacuum pods and buckets replaced this year with the 26r type kit I have and still keep the weight down, or loose some as I think the stock seats will go (one is currently remove so my 100 lb Yellow Lab "Beauregard" can ride in the Elan). As long as we have hijacked this thread, what are you using for synchro rings and synchro hubs? at the moment Dave Bean is selling Semi-close synchro rings for $106 USD, have you found the later rings and hubs to be suitable, they seem to be some what less expensive.

Gary

PS Steveww
I have the Ali block in stock but need the rest of the components to finish it.

PPS Ed At 145lbs, I can't give up the 30 lbs that you are speaking of, might be able to do 10 though.
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PostPost by: rgh0 » Fri Apr 15, 2005 10:16 am

Gary

I use the standard later post 66 syncro rings and hubs in my Elan box with Quaiffe close ratio internals which are designed to go with these. I have not been able to find these syncro components new in recent years and get second hand ones from old cortina boxes of the same vintage. These used the same syncro components but different gear ratios and gear change arrangements.

I have seen new steel syncro rings advertised lately but have not tried these so dont know how they compare with the original bronze ones or if anyone is making the bronze ones again.

The earlier pre 66 Lotus / Ford boxes used different syncro rings and hubs compared to the later ones reagardless whether close or semi close ratio. They are not interchangeable with the later semi close ratio ones without changing the rest of the box internals as well. The DB manual has a good discussion on all these issues.

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