Springs

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Printed on: 20/07/2024

Topic:

Topic author: Cymber
Subject: Springs
Posted on: 18/12/2007 12:42:49
Message:

My P Type springs have the bolted clips as all the references I have suggest is correct. They need new spacer tubes but the remains of the originals suggest that they were only about .050" thick. With a tube of this thickness the spring leaves are not held in contact when the spring deflects, is this correct or should I make thicker ones? I have a feeling that I have seen a reference to making D shaped spacers but can't remember where.

Maurice Blakey.

Replies:

Reply author: Mike
Replied on: 18/12/2007 15:29:49
Message:

The spring clip spacers or rollers should just kiss the leaf spring when under load. I have seen many original springs where there is a pronounce groove in the leaf spring as the roller has seized and no longer rotates then wears through the spring.

The spacers were about "0.050 thick however new spring leaves are probably in metric thickness so you may have lost some meat in the pack but still have the spring rate.

Jan and Bruce could give you some old rocker shaft spacers for the job!!!!!!!!!!

M ELLIS

Reply author: David Allison
Replied on: 19/12/2007 09:19:42
Message:

Mike is quite right - the "spacers" are in fact rollers.
They should not grip the springs at all.
If the rollers sieze - the springs get damaged very easily causing a stress raiser and spring breakage.
However that said it is normally the spring leaf one or two leaves above the roller which breaks.
Hope this answers your question.
Regards David

Reply author: Bruce Sutherland
Replied on: 19/12/2007 18:17:56
Message:

This spring correspondence has set me searching for more detailed information and I've found the following:
Extracts from the Eaton Springs website: www.eatonsprings.com

1) Leaf Spring banding clamp/clip û function/purpose
ôThe bands are called "Rebound Clips". Normally a spring does not break while it is under load. It breaks when the load is released and the spring is rebounding.
When under load each leaf is supported by the leaf below it and the leaf above it. When the load is released and the spring is rebounding the leaves fan out.
This is where the clips come into play. The clips will hold the leaves together as the spring rebounds, allowing the leaves that are banded together to support each other.ö

2) Inter-leaf lubrication
ôThe idea behind lubing between the leaves was to reduce inter-leaf friction.
Then in the early 50's the type of steel used to manufacture springs was changed to SAE5160 and the practice of lubricating between the leaves stopped.
Grease has an adverse effect on 5160 steel. The chemicals in the grease react with the steel and causes the steel to breakdown.ö

3) Leaf end type (square or ædiamond pointingÆ)
ôSquare ends: Concentrations of interleaf pressures, friction, and stress result in a very poor acting spring for light weight vehicles.
Diamond pointed ends: are the same as square cut except that the excess material is cut off. Diamond pointing will result in a better-stressed spring.
Square ends, or constant thickness ends are great for trucksààààààààhowever for the smoothest riding spring, the ends must be tapered.
Tapered leaf ends move the friction area away from the leaf ends and spreads it over a much larger area, resulting in less force needed to flex the springö

www.eatonsprings.com/Spring%20Tech%20101.pdf

I found this interesting and may prompt further (hopefully informed) discussion.

Happy Christmas to all.





Bruce.

Reply author: Mike
Replied on: 19/12/2007 18:58:41
Message:

Bruce,

With a MMM road spring anchored at one end only you could hardly call them rebound clips as the up and down movement of the spring lengthens and shortens the length of the spring running back to the trunion box. The rollers reduce the friction as compared to a clamp clip to allow the spring to move fore and aft.

Hope this provides further (hopefully informed) discussion as requested by Bruce

Ask Eaton Springs if they have heard of trunnion boxes at the rear anchoridge point because there is nothing on their web site that is pertinent to a MMM car.

Reply author: Bruce Sutherland
Replied on: 20/12/2007 01:01:58
Message:

The last respondent would appear to be largely in violent agreement with Eaton Springs!

Common engineering sense would point to the need for the leaf spring clamps/clips to allow:
(1) linear sliding motion between the spring leaves as the spring flexes and that a roller arrangement, properly dimensioned as previously described, should offer less friction in inter-leaf shear than a simple clamp.
(2) However the function of the 'rebound clips' in mitigating against leaf separation under spring load reversal is equally valid whether the design of the spring-end retention is by trunnion or shackle configurations.

Correct engineering analysis is valid from which-ever country it originates - so let us be more mature and NOT prompt apparent prejudices about the sources of well-reasoned information, please.

Bruce.

Reply author: Bob Stringfield
Replied on: 20/12/2007 11:39:08
Message:

Apropos of spring fitting - MG invoice No. R 4092 to J. E. Rushbrooke, original owner of PA 0603 - APP 186, subsequent to fitting a front-mounted Marshall supercharger.

' Fitting Vibrac axle side shafts.
Supplying and fitting extra leaves to front Road Springs'

Sadly, no mention is made of quantity or specification.

The original build sheets for our cars, obtainable, of course in photocopy form from the MGCC, are vital if re-building.

Get yours, if you haven't got them so far.

Is there any way of recognising a Vibrac half-shaft?

Merry Christmas to MMM Owners.

Reply author: Cymber
Replied on: 24/12/2007 21:45:42
Message:

I have the remains of what I believe to be original springs which have square ends.

Maurice.

Reply author: Mike
Replied on: 24/12/2007 22:12:39
Message:

Have a look at the service parts list either for a J2,PA/PB or NA/NB and the illustrations show the main leaf with one eye end at the front and the rear end square that goes into the trunnion box.

Makes sense really as you want a square end with maximum area in contact with the trunnion face, all other leaves are cropped at the end to spread the the edge distance in contact with the next spring to reduce contact stress.

M ELLIS

Reply author: Cymber
Replied on: 28/12/2007 21:38:03
Message:

Brian,
I can't be absolutely sure. They are well used springs removed in 1957 so could be original. They were replaced by new ones supplied by either Thompsons or Toulmins which had square ends, now, would these replacements be works or pattern parts?

Maurice.

Reply author: Mike
Replied on: 29/12/2007 19:36:12
Message:

Maurice,

I cannot see the works still supporting a car that went out of production 22 years from when you bought those springs. Indeed engine replacement parts etc were hard to come by in the 50`s / 60`s and often Thomsons or Toulmins struggled to get parts most of which were reworked old stuff.

The war also would have cleared stocks for scrap iron for the war effort. The Abingdon factory was cleared out to make room for the manufacture of aircraft nose sections, mini submarines etc.



M ELLIS

Reply author: tholden
Replied on: 29/12/2007 20:24:20
Message:

I can confirm that all original J springs were as Mike describes i.e.that the end of all leaves were tapered with the taper squared off at the end. The exception was the main leaf which for obvious reasons had a square end. Original springs were stamped sometimes on the inside and sometimes on the outside of the leaves with ( from memory since I am not crawling under the car to check !) BSG for I think British Spring Group and the date month and year.
I can also confirm that the spacers should revolve but the original spacers were made out of tube that was rolled and not seem welded so I dont think they lasted very long and are usually found to have jammed in one position with a flat worn on one side.
I always try to retain as many original leaves as possible when rebuilding springs since the original steel quality was vastly superior to any replacement springs I have seen. It is however usually necessary to have a new main leaf made.If you have any new intermediate leaves made the the ends should be tapered as per the originals for the reasons stated.
I make new clips and rollers where necessary and if you are running a supercharged car and need the front springs to be a little stiffer then this can easily be achieved by having a new main leaf made in the next metric thickness up and machining out the slots in your trunnions to suit. New bolts for the rollers can be made from standard coach bolts with the heads machined with a flat as per the originals if you so wish.

Terry Holden

Reply author: George Eagle
Replied on: 05/01/2008 20:35:50
Message:

I have checked the springs on L2023. They are stamped B.S.G. Mar 1933 which is also the date the car was manufactured. With the exception of the main leaf the ends are tapered.

As a matter of interest the springs on my NB are also tapered.

George

Reply author: Bob Stringfield
Replied on: 05/01/2008 21:58:27
Message:

When I owned L2023 I had those springs re-tempered and reset by the good craftsmen (sorry, craftspersons) at Jones Springs of Wolverhampton. I resisted their willingness to make new ones.

Reply author: David Allison
Replied on: 08/01/2008 15:22:20
Message:

The springs were originally sourced from a number of manufacturers - some of these supplied tapered ends and others square ends.

The majority of springs were sourced from a manufacturer in the West Midlands (they used still to be in business in the 1980's) after the war they renamed themselves GME springs and I think they are still in business now.
They always supplied square ends to the intemediate leaves - unless you paid an extra amount (probably only a few pennies) to cover the labour.

At the time you could specify things to suit your pocket in the same way I suppose you can now when you buy a car.
There was not real accepted "standard" because the cars were all supplied to very individual first owners.
Cars sold through the dealers were more standardised - but you could get non standard specifications on these cars too.
University Motors, Bellvue and Parade Motors were all suppliers of special in-house minor mods to make the car more individual.

Tapering the intemediate leaf's does not make the spring any better or worse than the square edges.
To some eyes it might appear more pleasing.

Like everything else - you pays yer money and takes yer choice!

Hope this helps
Regards David

Reply author: tholden
Replied on: 08/01/2008 21:47:27
Message:

David I dont all together agree with what you say.
As far as the J's are concerned I have seen and rebuilt lots of original springs as identified by the manufacturer and date stampings already mentioned. I still have plenty of them kicking around here and each and every one has tapered ends to the all the leaves except the main one.
When I rebuilt my first J2 back in the early 60's I had the benefit of a neighbour who had worked at MG's in the early 30's. He was a mind of information. When I was rebuilding the springs and had some new leaves made with straight ends he explained to me why I needed to taper them as per the originals for the very same reasons as Bruce has extracted from the Eaton web site.
I dont think your statement that tapering intermediary leaves is neither better or worse than straight ends is therefore correct.

It is of course true that MG changed suppliers on many items very frequently and in the difficult times of the early thirties they did all they could to source parts at the most competitive prices they could. I have no doubt that different manufacturers supplied road springs to MG in this period and that the specification could have been changed from model to model and as time moved along.

I cannot speak with certainty for other models but I reckon it is likely that the majority if not all the J's and possibly the L's had leaves with tapered ends originally fitted by the factory. I have some original works photos from early 33 which clearly show a J chassis with springs with tapered ends but these do not of course prove that every car had these fitted.

However many of these could have been changed very early in the cars life. Broken springs were quite common in the thirties when roads were not exactly up to todays standards and it is highly likely that replacement springs from the local garage or blacksmith would have had straight cut ends.

I doubt if we will ever know for sure unless someone can come up with some factory records to prove the point one way or the other but to me the balance of probability is that the leaves were tapered as standard and that this was done for good engineering reasons.


Terry Holden

Reply author: Gordon
Replied on: 09/01/2008 14:29:23
Message:

I am not wholly persuaded by the Eaton explanation. I have seen "diamond" shaped leaves that have worn their shape quite deeply into its mate. If you want to reduce the load at this point wouldn't it make more sense to taper the thickness at the end?

Gordon

Reply author: Oz34
Replied on: 20/03/2008 15:58:08
Message:

I've just been looking at one of the rear springs from my PA. They were on it & definitely looking rather old in 1966 & have square ends to intermediate leaves.

The trailing end of the bottom leaf is stamped "MG 505" & "BERRY". 505 is the MG part number for a P Type rear spring which I can see a manufacturer using when the cars were fairly current. Would they still be doing so after the war though? On the other hand the illustration in my parts list seems to show tapered ends so who knows; it looks as though it was indeed a question of different suppliers.

I tend to agree with Gordon that tapering in thickness must be useful. each leaf of my springs, with a sharp edge at its end, has cut its way into the one above. If that edge had been rounded off that effect must be lessened.

Dave

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