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Lotus 7 series 2 rear axle housing-free


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Hello Chris,

 

   I have a 62 7A with a 948cc engine and that rear axle.  Mine already has a crack and I would be interested in your spare axle.  I live in California.  Would it be possible for you to shIp?  Of course I will pay expenses.  

 

Thank you,

Dann Shively

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3 hours ago, Heloman said:

Hello Chris,

 

   I have a 62 7A with a 948cc engine and that rear axle.  Mine already has a crack and I would be interested in your spare axle.  I live in California.  Would it be possible for you to shIp?  Of course I will pay expenses.  

 

Thank you,

Dann Shively

Assume this is the bottom center mount on the diff, I think converting the lower arm trailing bush to a 1/2 inch spherical and spreading the diff mount over a larger area would prevent future cracking. Making a new arm and modding the diff, while keeping the originals sounds reasonable.

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If you think about it, the spherical bushing will produce the same fore/aft load as the original transverse bolt through bushings... The 'Stegosaurus plate' is the way to keep the axle flexing at the diff.

 

Dann - I had the same crack which was 'fixed' once by brazing - this did not hold up. Be sure it's properly welded.

 

My 1961 Seven America has a 948 now but had a twincam in a previous life, plus extra wide rear tires. This is what causes axle failure -- over-powering and over-tiring the car. All repaired, my 948cc Seven runs on original spec 3 1/2 Triumph Herald rims with 155 series tires. It drifts perfectly in rain and dry pavement, and I know that the axle is not being over-stressed.

 

Check here for details on options for the axle: https://www.simplesevens.org/history/t10axle/t10axle.htm

 

Cheers!

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Great info for any series 2 owner. I had not seen it before. I guess I should be very happy that my car has retained the series 1 suspension design, unaltered, in my series 1, 1959 # 475. It has the original A40 axle ( seems to be the same as AH Sprite Bugeye), modified by Lotus for attachment points according to my receipts from Lotus dated 1959. So it has no central diff pick-up point like series 2 and therefore no twisting of the housing as described for series 2. Not sure why they changed that when they went with the TR10 axle. The original design for lateral axle location has the right lower arm with a welded additional diagonal tube (making a wishbone) that connects from just inboard of the right brake area to a  square vertical central tubing member and pivots just a few cm back behind your left hip bone (they were all right hand drive).

Anyway, back when I was gathering parts such as the 1500 non-crossflow and dual 40DCOE set-up, I sort of recall the ex-racer saying he had no use for the bare TR10 housing but that I would certainly need it if mine broke. But of course it has been of no use on a series 1 so needs a new home.

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I think the original bush in new condition would actually be better for traction loads than a spherical since it would provide some compliance to absorb the peak load, but once it gets oily and/or deteriorates a bit, it could be worse as DSK indicated in the link you provided. A spherical would be unaffected less affected by a leak or the twisting of the original type rubber from roll or one wheel bump.

Here is a cortina axle which could be further reinforced, but it already looks much better. I guess the cortina has a much longer arm with less angular change so the bush can be rotated 90 for no bind in roll, plus the flanges are further apart. The steg seems a bit extreme if you are not racing and just want better reliability.cortina.thumb.JPG.1f4ce24db52439955b6d2b7adaead71f.JPG

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15 hours ago, SevenAmerica said:

If you think about it, the spherical bushing will produce the same fore/aft load as the original transverse bolt through bushings... The 'Stegosaurus plate' is the way to keep the axle flexing at the diff.

 

Dann - I had the same crack which was 'fixed' once by brazing - this did not hold up. Be sure it's properly welded.

 

My 1961 Seven America has a 948 now but had a twincam in a previous life, plus extra wide rear tires. This is what causes axle failure -- over-powering and over-tiring the car. All repaired, my 948cc Seven runs on original spec 3 1/2 Triumph Herald rims with 155 series tires. It drifts perfectly in rain and dry pavement, and I know that the axle is not being over-stressed.

 

Check here for details on options for the axle: https://www.simplesevens.org/history/t10axle/t10axle.htm

 

Cheers!

Thanks, John.   Way back when the crack in mine was brazed as well and started seeping.  The previous owner applied epoxy which stopped the seeping for awhile but is leaking a little now.  Will have it properly welded or replaced.

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If a crack has been brazed it will be very difficult to weld. If it was brazed well it will have spread deep into the crack making it very difficult to clean the area before welding. Welding rod a brazing rod do not mix.  Talk to your favorite welder for his opinion. 

 

Graham 

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Graham-yes- we were just discussing that. An extreme cleaning and then a small, thin mild steel plate bent as precisely as possible to fit over the crack and re-brazed ( not welded, as you correctly caution) might work. I recall from "Welding and heat treating"class  in the engineering department at Penn State just how strong a lap joint can be if brazed properly. Without a plate it would essentially be a butt joint and might just fail again. That all assumes future use in low to medium stress conditions so no slicks or high torque applied.

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Brazing is high temp soldering. The parts have to be clean and a good fit, but if the surface area is good the joint will be very strong. The two surfaces have to touch, then as the braze flows it creates an alloy between the 2 surfaces.  When you solder something it not the solder that creates the joint. Solder is a soft as butter but can make some amazingly strong joints. If the joint fits well and the right temperature is used an allow is created that bridges the 2 metals creating the joint. 

 

Graham  

Edited by fastg
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The engineer who welded mine (after I ground out all the brazing), built up a weld on the inside and on the outside of the vertical crack on the backside of the diff cover. He's successfully raced his 1500-powered Seven (Tom Robertson's "lightest Seven ever built - ref back to DSK story on SimpleSevens: https://www.simplesevens.org/dsk/index.htm) across the country in SCCA, running with the T10 axle, so I trust him :-) Anyhow, he knows I'm running the original spec skinny wheels and tires, so I trust that he's comfortable with his work and my screamin' 37bhp (at the wheels, but that's another story soon SimpleSevens you'll have to find by yourself!).

 

Cheers!

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