Lotus Elan

Nasty noises (#34,978)

PostPost by: yandy » Wed Mar 04, 2009 2:06 pm

I suffered a sense of humour failure 100 miles from home last night when caught in all that monsoon rain we got in the Southwest. That followed an alternator failure which would have stopped me quicker if the wipers hadn't also failed earlier (possibly related).

All that however came on top of an infinately more worrying development, your solicited opinions of which, I court with dread.

I have a regular scraping noise (one per revolution of the wheel) coming from the rear LHS and more pronounced when cornering right. Jacking and turning the wheel by hand doesn't replicate the noise.

Please break it to me gently!

Thanks,

Andy
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PostPost by: tcsoar » Wed Mar 04, 2009 2:51 pm

Hi,

Have you looked at the back of the wheel to see if it is fouling the bolt heads on the a-frame, indication towards worn bushes or possible wheel bearing failure. Is the scraping a harsh metalic sound? If not while you are round the back of the wheel have a look at the drive shaft, maybe something caught there?

Chris.
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PostPost by: peterako » Wed Mar 04, 2009 3:03 pm

Could also be bearings{?}

But more likely wheel fouling on something.

How's your handbrake?

Remember, jacking the car up will have the suspension at a totally different angle/geometry to when it's on the road.

In either case, it should be easily recified once identified.

It tool me over a year to fix a clicking in my rear drive....checked the propshaft, driveshafts, cv joints, handbrake etc. etc. before it was tracked down to a broken top diff mount.....but I AM slow :)

Take care,
Peter
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PostPost by: yandy » Wed Mar 04, 2009 3:24 pm

Thanks Peter and Chris - so far, reasonably comforting.

Good point! I've seen and heard that wheel scraping effect before on a car that had recently had PM repro alloys fitted after having had steelies all its life, but hadn't considered (in my black mood) that the same could occur on my car by a progressive failure of something relatively obvious and straightforward as bushes.

It's definitely not the handbrake though. I've just replaced the linkage bolts with something beefier than the 1.5mm things PO had fitted and backed the brakes off a bit to take the extra diamater into account. They were my first suspect so I backed them off further to be sure until I had no functioning handbrake and still a nasty noise.

Anyway, I'm already feeling cheerier about it and unless anyone wants to propose anything much scarier and deep inside, then I'll remain hopeful until I can check it again tomorrow.

Cheers,

Andy
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Todays top tip: create a spooky lighting effect by forgetting to switch off and remove your torch from the nose area before refitting the grille.
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PostPost by: paddy » Wed Mar 04, 2009 3:57 pm

We had the same question come up about a week ago. As I recall the options we thought of were:

- bearing failure, causing wheel to move laterally (wobble), fouling A-frame bolts or wheelarch
- as above, fouling brake line (!)
- bearing failure, causing wheel to move axially (end float), brake disc fouling caliper
- A-frame bush failure, causing wheel to foul A-frame bolts
- wheel loose or incorrectly seating due to drive pegs
- hub loose on driveshaft

Apparently these were all things reported as having occurred previously.

Paddy
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PostPost by: msd1107 » Wed Mar 04, 2009 5:07 pm

I had an axle fail and the wheel come off while I was on the freeway at 75mph after hearing a small noise for a few days. There is a documented stress riser on the axle and it may take 40 years to propagate far enough to fail.

I believe the Dave Bean catalogue talks about this.

David
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PostPost by: gerrym » Thu Mar 05, 2009 8:51 am

David, as many of us on this side of the "pond" don't have and don't have any need to buy a Dave Been catalogue, is there an alternative source from where we can get a description of the stress raiser problem. Preferably on-line.

Regards

Gerry
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PostPost by: elj221c » Thu Mar 05, 2009 8:54 am

Andy,
Paddy forgot one. Doesn't sound likely in your case I'm afraid but do check the prop UJs for wear.
Gerry, there is a PDF somewhere of the page which relates to hub and shaft care.
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PostPost by: iain.hamilton » Thu Mar 05, 2009 11:00 am

I had this, and it turned out to be harmless. I had stick on balance weights that just touched the end of the Aframe...

best regards, iain
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PostPost by: yandy » Thu Mar 05, 2009 11:08 am

Thanks all - lots of good suggestions, and not many of them too disturbing. I'd be checking it now if the car hadn't disappeared under a pile of unscheduled snow. Will report back...

Andy
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PostPost by: RotoFlexible » Thu Mar 05, 2009 2:34 pm

gerrym wrote:David, as many of us on this side of the "pond" don't have and don't have any need to buy a Dave Been catalogue, is there an alternative source from where we can get a description of the stress raiser problem. Preferably on-line.


The Dave Bean catalog is worth obtaining even if you never buy anything from DB. It is full of reliable information that is hard to find anywhere else. (See the "Shims" discussion going on elsewhere.) It's one of the Pillars of Wisdom for Elan owners - others being the Buckland book, Miles Wilkins' Twin Cam book, this forum. (I don't know if there are seven total.) Dave Bean doesn't have much of a website (their latest "news" dates from Oct. '07, the "Specials" page was last updated a year ago) and the catalog is only available on paper.
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PostPost by: msd1107 » Thu Mar 05, 2009 7:41 pm

RE: Dave Bean catalogue not across the pond:

I can't post every thing in the Bean catalogue, because there is an illustration of the axle shaft and hub. All this is on page D3.

But summarizing what they say:

"If you are using your Lotus in competition you are in jeopardy of overstressing the outboard stub axles. The failure mode is to crack and eventually fail just outboard the outer bearing, underneath the hub. This is to be expected, as it is the confluence of the point of greatest bending moment (between hub and bearing), a stress riser caused by the axle key, and the taper corner."

And paraphrasing:

"Chamfer the corner of the hub where the shaft enters.

Polish the corner of the shaft where the taper changes to constant diameter section.This rounds the abrupt transition from constant diameter to taper.

The axle has a groove for the key. Taper or round the end of the key. Grind radius on groove edges past the end of the key."

They go on to say that doing this to a used axle may actually start the process, so don't pull your existing shafts to do this.

They recommend replacing existing shafts with high alloy heavy duty shafts that have been known to endure seasons of racing without a failure.

And, of course, you have to remove the shafts first, which is sure to brighten your Sunday morning!

David
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