Lotus Elan

Differential - washers

PostPost by: jono » Tue Sep 20, 2011 4:18 pm

I am a bit worried about the washers on my differential mountings as it seems I may have missed one out :roll:

What I would like to know is if it is critical before I fit the petrol tank. I do have the opportunity to change it now but it will still be a bu66er and I only want to do it if it really presents a failure risk in use.

It's a plus 2 with a Sypder spaceframe chassis and I have fitted TTR uprated diff mounts and tie rod mounts. New Mick Miller shafts are fitted and I have also fitted a diff brace. The engine is around 135bhp and I will not be thrashing her. It has the later, stronger, diff casing.

I have fitted new diff mounting bolts and installed one large washer between the top of the diff brace and the TTR mounts. I have installed the bolts through the lower diff ears and a further large washer on the top of the TTR mounts before the nyloc.

I have installed the 2 thick standard diamater washers between the bolt heads and the lower diff ears but I have not fitted the larger washer between those 2 thick std washers and the diff ears.

It's all very solid and looks 'right' but will the ommission of the larger washer to the lower diff ears cause a problem?

I would welcome any views.

Cheers

Jon
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PostPost by: 512BB » Tue Sep 20, 2011 6:58 pm

Jon,

Having deciphered what I think you have described, I am sure that you do not need one of the large dia washers under the bolt heads. In fact, I am not sure why you even need 2 of the smaller plain washers under the bolt head, I have only ever used one, albeit a very thick one. Does the workshop manual show 2 of those?, its been quite a while since I last refered to it.

Leslie
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PostPost by: jono » Tue Sep 20, 2011 9:01 pm

Leslie,

I have followed the sequence shown in the attached but have omitted the large washer on the bottom (but fitted the 2 smaller ones) and have only used 1 very large washer on the top (only 1 is permitted if you fit the diff brace).

Jon
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Section R Page 4.pdf
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PostPost by: 512BB » Wed Sep 21, 2011 6:34 pm

Jon,

I follow that sequence as well, but with the bolt the other way up, I only have Elans, not +2s, and omitting one of the smaller dia washers under the head of the bolt, as I said, I cannot for the life of me see a need for 2 there.

Atb,

Leslie

Oh, and by the way, who painted your +2, it looks fabulous, and are you 100% happy with it?
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PostPost by: jono » Mon Apr 23, 2012 9:35 am

I am returning to this thread being at a critical stage of my build.

Leslie - thank you for your comments. I am still worried though, perhaps irrationally so :shock:

I suppose what I am concerned about is unless a large spreading washer is used beneath the diff ear (and it is after all machined to accept such a washer) the torque reaction will not be spread across the full mounting face of the diff ear and will hence be concentrated through the bolt head and standard size washers over a smaller area.

Should this be a concern?

All comments appreciated. I don't want to have to undo everything but I will do if there is any doubt. Don't want it to fail half way up the Stelvio :oops:

Best regards

Jon
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PostPost by: 512BB » Mon Apr 23, 2012 10:29 am

Jon,

Still stand by what I posted before. Cannot see the need for the 2 smaller washers under the bolt head, or nut, depending on which way up, or down, you fit the bolt. So long as you have a nice thick, approx 1" dia load spreading washer against the underside of the diff ear, that is correct.

Out of interest, are you using an early alloy housing, or the later type, with the strengthened ears, and a recessed part underneath the ears, that a nice thick and wide washer fits into?

Leslie
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PostPost by: jono » Mon Apr 23, 2012 10:59 am

Leslie,

You have confirmed my suspicions! I only have 2 std dia washers under the bottom diff ear (my poor explanation originally I think)

Yes, it is the later diff housing with the larger ears I have which, as you say, is machined to take a large thick washer.

I have ordered new bolts and thick washers from Sue this morning.

Regards

Jon
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PostPost by: garyeanderson » Mon Apr 23, 2012 11:03 am

Jon

This is how I install the bolts. I think that it's close to what the folks that designed and built them were trying to accomplish. This is for the Elan chassis (Sows Ear Chassis topic in Elans) not the plus2 but I really don't think there is a lot of difference in the thoughts behind the installation. The (2) small washers are to either make of the distance due to a longer than needed bolt or just a doubler to give the washer some thickness. "My guess" is they wanted to give it some thickness without going to a special washer, I found a thick and fairly large diameter washer for just under the head of the bolt. then a even larger diameter washer that covers the entire ear of the alloy lug of the case. I don't have the Sprint type brace over the diff so I use a pair of the 1/8 inch thick 2 inch diameter spacer washers. these are important in that the space the diff down the correct distance so the diff case ear doesn't hit the chassis at the back (see picture),
diff hanger bolt.JPG and

The bolts are not done up at all, currently finger tight only now. Its a tight fit in there and the diff needs to be located properly as when driven as it should to enjoy it will move some and if it hits the chassis you will either hear it or have to deal with it ,
diff hanger bolt1.JPG and


Gary

There are more photos on page 3, post twelve of the Sows Ear Chassis topic
elan-f14/sows-ear-chassis-t24752-30.html
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