Lotus Elan

On car propshaft balancing

PostPost by: JonB » Tue Jan 14, 2020 2:12 pm

OK, so I've sort of done it, using a Jubilee clip and trial and error. I didn't like the idea of climbing under the car with the drive train running so I put the chalk on the end of my jack lever and made the initial mark kneeling at the side of the car. I dispensed with the cup of water because I could feel the vibration sitting in the car.

So, start the engine, put it in 4th, raise revs to 70mph indicated, note vibration levels, stop, adjust, rinse and repeat. After around seven or eight iterations I had it reasonably good. On a test run in the horrible rain it is much improved though not perfect. I shall also try swapping front and rear wheels in case either of the rears are out of balance but that can wait for a nicer day. My garage is damp and cold right now.. :(

Meanwhile Dave Mac Propshafts came back to me regarding price. ?105+VAT including carriage both ways, which isn't bad at all. Hmmm...
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PostPost by: RichardHawkins » Tue Jan 14, 2020 7:55 pm

John,

The company I used was ims-Ltd.co.uk in Birmingham, I bought a complete prop shaft for ?180 3 years ago.

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PostPost by: 2cams70 » Tue Jan 14, 2020 10:01 pm

JonB wrote:. After around seven or eight iterations I had it reasonably good. On a test run in the horrible rain it is much improved though not perfec


Like I said propshafts are balanced at both ends and the balance weights are welded on. Don't waste your time with jubilee clips. If it's not properly balanced at the front the gearbox extension housing bush will wear excessively and the oil seal will leak.
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PostPost by: JonB » Wed Jan 15, 2020 9:58 am

Indeed. As I said, it?s not perfect, but it is improved. In particular a deep vibration at 40mph that was concerning me has gone and the high speed vibration is much less, though still there. So I won?t consider it a wasted exercise.

I think I will get it done right, once the weather clears up. It really is a time consuming job. I?d like to fit new nuts and bolts to the flanges too, as mine are getting a bit rounded.

Does anyone know what the size / specification is for the flange bolts? Heads are 1/2 inch and they have a fine thread. That?s all I know...
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PostPost by: nmauduit » Wed Jan 15, 2020 4:57 pm

JonB wrote:Indeed. As I said, it?s not perfect, but it is improved. In particular a deep vibration at 40mph that was concerning me has gone and the high speed vibration is much less, though still there. So I won?t consider it a wasted exercise.

it should be reasonably clear to distinguish wheel unbalance from propshaft unbalance du to the reduction ratio of the diff (wheel unbalance tend to occur at a certain speed where the rotation frequency corresponds to a natural resonnance of the car - on mine which used to lose wheel weights because of lack of clearance it was about 95 kph iirc or ~60mph, so considering the same body resonance frequency and 13" wheel rim diameter as well as comparable tire wall thickness - 70 in my case - I would guess that the low speed variation was induced at twice the propshaft rotationnal speed, possibly due to reassembly with a twist as was suggested above)
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PostPost by: mbell » Wed Jan 15, 2020 7:20 pm

JonB wrote:Does anyone know what the size / specification is for the flange bolts?


Not fully, I believe they are 5/16" fine thread, not sure on the length. I do remember you need bolts with extended shoulders to engage both flanges, so standard 5/16" bolts of the right length aren't correct.

I just got mine from one of the parts suppliers to save me the hassle of finding them myself.
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PostPost by: alan.barker » Fri Jan 17, 2020 4:55 pm

Hi JonB,
I feel sorry for you.
What a pity i see that when you are so close to getting your +2 to run correctly you have decided to throw in the Towel. You only need to balance the Prop Shaft by a professional and get 4 Tyres the original size.
Please don't make a bad decision after all the work.
best regards
Alan
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PostPost by: JonB » Fri Jan 17, 2020 6:11 pm

Hi Alan

The way the market is at the moment I doubt it?ll be leaving me any time soon.
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PostPost by: vincereynard » Fri Jan 17, 2020 10:53 pm

What's this! What's this! What's this!

Slipping away when so close. I recon its the summer that worries you.

You're afraid you might consider a sheepskin seat cover.
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PostPost by: gino1 » Thu Jan 23, 2020 12:50 pm

Change the nose on your propshaft and the bush inside the tail of your gearbox and you'll have probably fixed your problem...

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PostPost by: h20hamelan » Thu Jan 23, 2020 4:34 pm

If that doesn’t fix it.

viewtopic.php?f=37&t=37586&start=

Think you’ve got a real nice car. Can’t imagin how frustrated...

Do any local garages have the wireless (or wired) magnetic or other microphones.
I know the sound can travel/resonate throughout the chassis. I think with some testing, you will have it figured out. :wink:
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PostPost by: JonB » Wed Apr 01, 2020 10:38 am

OK, update: As we have a nice lockdown in progress I've mailed Dave Mac to see if they are still working. If so, I'll pull the shaft and send it.
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PostPost by: alan.barker » Wed Apr 01, 2020 11:10 am

Bravo Jon,
do the job correctly.
At last something positive from the shutdown
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PostPost by: JonB » Wed Apr 01, 2020 1:53 pm

Not quite:

davemac wrote:We are currently closed for the COVID-19 shutdown protection period.

The factory is fully closed and we are working from home where we can.

Further updates will be on our website :- davemacprops.co.uk

Dave Mac Propshafts



..dagnammit.
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PostPost by: h20hamelan » Wed Apr 01, 2020 2:55 pm

Betcha the lorry shops are open
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