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Early Cooper 500 F3


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#1 rbm

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Posted 22 May 2007 - 08:41

The very first Cooper 500 cars had the JAP speedway engines mounted on 2 leaf springs bolted / clamped across the rear chassis legs.
Anyone any idea when this idea was dropped in favor of the solid metal plate mountings?

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#2 roadmap

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Posted 22 May 2007 - 11:29

I have three Amal 27/103 carbs that were used also on the speedway bikes. I think they were used on the cooper japs.

#3 Dutchy

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Posted 22 May 2007 - 11:42

Didn't they break at the first meeting they competed in, which would be Prescott in 1946? I don't have any information to hand but I remember reading they had to weld in solid mountings overnight to cure the problem

#4 rbm

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Posted 22 May 2007 - 12:09

the first prototype used hollow bar as the engine bearers and these snapped, a quick overnight repair saw bits of solid bar (cut from a plough handle so the story goes), these also broke fairly quickly and were replaced with 2 leaf springs.

Now the leaf spring were on the first batch of cars, up to our Cooper chassis number 10 at least as the pictures of ours when recovered in a scrap condition from Kenya has no cross members fitted to the cahssis to mount the engine too.

so the question is , was the leaf spring idea only used on the 1st batch of 12 ( I still think 11 and 1 modified prototype) cars or did it carry on longer, and what was the reason it was dropped (they didn't work?)



o/t James finally crossed a finish line ! VSCC Cadwell

#5 Dutchy

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Posted 22 May 2007 - 12:51

Congratulations Richard!
You must be chufffed after all the travails of last year

#6 HiRich

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Posted 22 May 2007 - 13:09

Richard,
This is quite an odd one.

The original design of T2 had solid mounts. But as James says, these failed completely on it's first run (Prescott, 27/06/48). These were replaced on the day. The design failed again (Prescott, August), and the leaf spring mounting was prepared for Brighton, a week later.

I can find no reference to T3's mounts. Given how late in 1946 the springs were applied, I would guess it was also fitted with them. However, as you know, detail pictures are rare indeed.

When we get to the production Mk IIs in 1948, information is still limited (though you have a better reference in your garage), but I believe the springs had now been ditched. I base this on:
- Every image I see seems to show substantial tubular crossmembers
- In Austen May's book he refers to the crossmembers failing (in 1950) on his ex-Moss Mk II. The initial fix was to ram a solid bar through the broken tube and weld it in place.
- There's a later reference (which I can't find) in the book to engine mounts - May (and possibly Coldham? Otherwise Dryden) being "the only original cars still fitted with the original mountings".
May makes several mentions of engine mounts, and everything suggests something like the plate-style design onto cross tube that you have now, and which developed through all the later models.
We know May/Moss' car was one of the earliest batch, but that appears to contradict what you see on 10. If your car did not have crossmembers, what did it have?

As to why the springs were deleted, I would suggest:
- Weight (probably John's instigation)
- Cost (probably Charles)
- Accommodating the 1,000s and Norton engines
- Keeping both chains tensioned properly.
As an aside, the only 500 I know that successfully suspended the engine was the Viking of Stuart Dane (a British ex-pat in California). He rigidly mounted the entire drivetrain in a subframe which was then mounted to the chassis with rubber plates. Somewhere I have an article on the car - both mounting and the car were successful, but chain tension was the main problem until the entire drivetrain was isolated.

#7 rbm

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Posted 22 May 2007 - 14:17

My thoughts on the spring engine mounts come from 1. the picture showing the Cooper mk2 and prototype line up, in the front of the cars is a JAP with 2 leaf springs fitted (which prompted this whole new line of questions).
my car had 2 extra tubula x-members fitted by "Tim" Cameron,which the engine mounts too. In the early pictures of the car when it came back there are 8 tubed (?) hole vertically through the main chassis rails, the front 2 pairs just behind the tubular x member behind the seat.
Now the pictures that "Tim" took showing the Spike car and mine as chassis, the spike car has the extra x members - which were coipied for mine car.
Posted Image
not the clearest picture, Banana split in front and kenya behind if you look at the rear end (left) you can see an extra x member (black tube)with a set of engine plates attached on the Banana Split.
Posted Image
this show the rear of the "kenya" showing the pairs of holes in the rear chassis rails behind the tubula x member (seat back x member).
Posted Image
"Kenya" in mock up stage showing the extra xmembers and later type engine mounts(2 tubes next to each other at the right hand end).

In the DCN cooper book there is a picture of the first batch being asssembled on the jigs and these cars do not have the extra x-members and one seams to show the leaf springs.

#8 HiRich

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Posted 23 May 2007 - 12:05

Intriguing. Clearly the Mk IIs started with some form of bolt-in assembly (though perhaps solid mounting rather than leaves?).

I'll take a closer look at May's first-hand account and see what clues it can give us. The other good sources would be the 1948 Iota magazines (I don't have any that early), and perhaps Woody might have a clue?

#9 hodsonaj

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Posted 23 May 2007 - 20:27

Richard
Could I add my two penn'orth here. As you know I have chassis no 20 also acquired from the Camerons. The engine in mine is mounted on two substantial cross members which are bolted to the top of the chassis rails through the 8 tubed holes you mention. There is nothing on my chassis to suggest that the motor was mounted in any other way, although there has been plenty of welding in the general area!! The cross members are slotted to allow a certain amount of movement for chain adjustment. Am I right in thinking that Banana Split was a V Twin and maybe had a different mounting?

As to Austen May, he acquired the Moss car in late 1948/early 1949 and the comment about only two cars still having the original leaf spring mounting refers to his ex-Moss car and that owned by Peter Collins at the time of their entries for 1949 Easter Monday Goodwood. He goes on to say that a set of solid mountings were received from Coopers which he fitted just prior to the Silverstone Meeting in May 1949 - so he did not delay too long in getting rid of the springs!

BTW we started ours for the first time last week and it went under its own steam for the first time since 1963 - brilliant
Tony Hodson

#10 rbm

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Posted 24 May 2007 - 09:01

Hi Tony,

good to see another mk2 up and running (in time for Anglsey ?).
Yes Banana Split was a V twin from day 1, The thing that got me thinking about this is the mk2 line up picture in DCN Cooper book, the JAP infont of the cars is fitted with leaf springs, but as it says in May's most of them were dropped fairly early, which may help me as the "kenya" was still on the leaf spring in the late 50's - or so the story goes.
Posted Image
no.20 on the left and no.10 "kenya" mk2's

could you post a picture of your engine mounting system?

#11 HiRich

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Posted 24 May 2007 - 12:40

Thanks for the tip, Tony. May's exact words are:
"Collins and I discovered that we were the only two Cooper drivers with the engine of our cars still mounted on leaf springs in the chassis, all the other cars, except Brandon's prototype, using the "solid" mountings we had heard about. These consisted of a cradle of light steel plate welded to angle iron transverse members having T-plates for the actual attachment to the chassis side-members" (pp86).

This was the Goodwood Easter Meeting, 18/04/49. I know of a good half dozen Mk IIs in the race, plus Abecassis with the Twin. It was Collins' first race, in a Mk II (and the evidence is that he was the first owner). It's possible these weren't the "last two", rather the last of the regular racers (there's at least one car that barely saw action until 1950).

So:
- T3 retained springs through its time with Brandon
- Springs were used on at least the early Mk IIs, at least for the 500s. Whilst Twins might have had a different installation from the start, it still seems possible that all the 500s had at least the same chassis mount/holes.
- The upgrade came in probably at some point in 1948 (May-December). I would suggest the Grand Prix (October) as a key moment, as Cooper supplied modifications (large scuttle fuel tank, cooling ears) - except Moss appeared at this race and clearly didn't have the engine mount upgrade. I find it strange that customers would have such a risky upgrade in the off-season without it having been well-proven through 1948.

It happened (sorry for doubting you Richard). And we have an idea of how, thanks to May. Exactly when and why we're unsure, and I think only Iota (or a Cooper staffer) will ever give us those answers.