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Connecting Rod Balancing


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#1 rogerguzzi

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Posted 28 July 2017 - 06:53 PM

Hello All

             I thought I would start this thread although I mentioned it in Pistons

 

I seem to be getting Nowhere in the con rod balancing? the first C***k up was I ordered the wrong scales(500g instead of 2000g!) but they are only about £7 so ordered 2000g ones.

 

My problem is I have roughly ground and polished all the rods and overall they are taking No2 as lightest 1 = +3g & 3&4 +5g so quite close

 

But when I put them on my Test rigs(yes plural!)  I can not get consistent  readings? (I am close to buying a set of those fancy ones in desperation!) and the readings are nothing like the total weight error?

 

These are photos of my 2? test rigs

 

So what am I doing wrong? and how close should I aim for?

 

Of course it could be these cheap scales?(they big are enough to balance rods on their own and end to end)

 

Plus I have weighed the big end caps on there own and that is were the difference is?

 

Very Frustrated Roger

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#2 Nick Jones

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Posted 29 July 2017 - 09:07 AM

I followed a similar path when doing the last lot of Vitesse ones (though your rigs are rather more nicely made) and had similar issues.  In the end they were finished off by the guy who did my other engine work (he did say they were very close though).

 

Other times I've just contented myself with matching the overall weight.

 

Seems to be rig design and solidity that determines accuracy / repeatability.  This is a nice one......

<iframe width="640" height="360" src="https://www.youtube....ed/QLpiF0E0EJU"frameborder="0" allowfullscreen></iframe>

 

......though I don't really see why your latest shouldn't work as well.

 

Nick



#3 oldtuckunder

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Posted 29 July 2017 - 10:47 AM

Looking good Roger, only comment would be that unless you know you have a set of identical weight bolts, you should be weighing with numbered bolts in situe. The set of ARP bolts that came new with my new rods were out over the set by over 0.5g actually as much as the promised difference in the rod weights.

 

A bit anal but I now ensure that when stripping engine I keep each pair of bolts with its respective cap.

 

Alan 



#4 rogerguzzi

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Posted 29 July 2017 - 12:12 PM

Hello Alan

                I have decided on a new set of standard bolts from Revingtons.

 

They came today and I have weighed them and they are very close max 32.09g min 31.92 so only 0.17g difference.

 

The old ones were about 0.5g difference.

 

I have had another go at my Mk2 jig and set it dead level and fixed the scales and the the bit that goes on them so it is exactly the same position each time and things seem a bit better.

 

So I will get them a close as I can! which has got to be better than they were?

 

When I take them for shot peening should I fit the new bolts or the old ones?

 

How is the drive shaft?

 

Roger



#5 oldtuckunder

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Posted 29 July 2017 - 02:22 PM

 

 

 

When I take them for shot peening should I fit the new bolts or the old ones?

 

How is the drive shaft?

 

 

 

Me I think I'd fit old ones

 

Just stripping rear end out this afternoon, some parts even turned up today after being ordered mid/late yesterday, including an unexpected pair of Seiko wheel bearings from non Triumph Spares supplier which came as part of a kit where I was expecting to throw the bearings away. According to a Friend who ran a bearing company until a couple of years ago, Seiko and Yoko are about as good as it gets, couldn't track down any Seiko but have a pair of Yoko's on the way, so looks like I will have two good bearing sets!

 

Alan



#6 JohnD

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Posted 30 July 2017 - 08:52 AM

All the weighing rigs Ive seen (online) use chain, not wire, to suspend the free end. This should allow it more freedom to assume the same angle.
John

#7 JohnD

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Posted 30 July 2017 - 12:25 PM

All the rigs I've seen (online) have suspended the free end on a chain.
Maybe this allows the free end more, er, freedom an doesn't bias its position.

#8 triumphlux

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Posted 30 July 2017 - 01:45 PM

I also spend some time balancing conrods ....... and my fancy setup was also unstable :unsure:

 

This is what turned out to work fine in the end, I marked the inner diameters accurately on the balances and I was able to get the same weights :yes:

 

Very simple setup, BUT it worked.

 



#9 triumphlux

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Posted 30 July 2017 - 01:47 PM

Picture to go with previous post

 

1300_Pleuel_300307_FORUM.jpg

 

JC

 

 



#10 rogerguzzi

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Posted 31 July 2017 - 07:44 AM

Hello JC

             I have a second set of scales on the way so I will try that method as it looks so easy.

 

I could use the plastic bungs I have made to fit the big and little ends to locate the con rods on the scales(a bit if double sided tape)

 

Roger

 

ps A chap was telling me on Saturday how the old boys used to balance con rods they would hang them on 2 nails on the wall by 2 elastic bands and make a line under each one to compare them!



#11 rogerguzzi

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Posted 01 August 2017 - 06:33 PM

Hello All

             I have finally finished polishing and balancing the con rods!

 

I recon I have got them within 0.6gm of each other! and after weighting the pistons on the new scales I think if I mix and match weights I can get the total weight within 0.3gm for the set.

 

I think the total weight reduction is as near as dam it 35gms which I recon to be just about 5%

 

Not that will make much difference but they will all be the same.

 

Now what shall I do next? I am still undecided whether to deck the block as there is a bit of water damage which I think would take about 0.010" to remove which would bugger the recesses up? so its either get them re cut(which would mean the head would have to be skimmed as well to get to 9.5 to 1) or remove them completely? then the head may be close to 9.5 to 1(need to do a bit of measuring and head scratching!)

 

I may just have a go at the new pump and face the ends down and pin the end plate so it is central not wobbling about on the oversize holes!!!!!!

 

My piece of aluminium bronze tube has arrived so I could have a go at making some thrusts(enough for about 15 complete circles)depending how much I scrap?

 

I started to make a jig to bore the rockers to fit bushes and reface them!

 

Or I could start clean the NOS cylinder head ports up(perhaps not yet fed up with grinding dust for now)or machine chambers as Kas Kastner shows?

 

Roger

 

 

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#12 triumphlux

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Posted 01 August 2017 - 07:56 PM

Good job :yes: 

JC



#13 rogerguzzi

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Posted 01 August 2017 - 08:19 PM

Hello All

             How do I mark them now they are polished? I do not want to put centre dot marks or my number punches?

 

I suppose I could do with a etching pen? any ideas?

 

Roger



#14 nang

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Posted 02 August 2017 - 02:30 AM

Permanent marker ? One to four strokes.

Tony.



#15 JohnD

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Posted 02 August 2017 - 08:59 AM

Why mark them?   No need - they are identical.

John


Edited by JohnD, 02 August 2017 - 08:59 AM.


#16 rogerguzzi

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Posted 02 August 2017 - 10:36 AM

Why mark them?   No need - they are identical.

John

Hello John

                 The end caps would probably not fit as I thought they were machined as a pair?(not checked but will look)

 

Roger



#17 thebrookster

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Posted 02 August 2017 - 10:59 AM

Hello All

             How do I mark them now they are polished? I do not want to put centre dot marks or my number punches?

 

I suppose I could do with a etching pen? any ideas?

 

Roger

Permanent Marker or Paint Marker, this is how we mark such things on ships.

 

Don't number them per sae, rather do as Tony suggests and use strokes, ACROSS the cap and rod (so when fitted they match). Do each rod in a separate location, as this then provides a very simply visual reference when re-installing. (I like white or yellow paint marker myself, I find this is the easiest colour to spot on polished metal.)

 

Cheers,

 

Phil



#18 JohnD

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Posted 02 August 2017 - 01:12 PM

Why would you need to take more than one rod apart at the same time?

John



#19 GT6MK3

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Posted 02 August 2017 - 03:51 PM

I'd Dremel dot them all with the finest possible burr, on the caps and rods, all on a high side so I knew how they go back together.  Avoids stress risers from punching, but lives through ball peening.

 

C. 



#20 thebrookster

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Posted 03 August 2017 - 09:05 PM

Why would you need to take more than one rod apart at the same time?

John

 

Normally you don't, but it covers your rear end nicely for that one time you have over enthusiastic assistance. I learned this from experience, and generally find that forming "good" habits at work transfer well to home stuff. Less chance of over-enthusiastic assistance maybe at home, but blonde/senior moments can and do still occur :P :P

 

Phil






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