The "Chapman" strut.

[elansprint71]

In the Lotus Elan workshop manual, Section D- Rear Suspension, paragraph D1-General Description it says-

"The rear suspension is of the fully independent Chapman strut type, incorporating coil springs and dampers".

In Rob in Read's excellent book Colin Chapman's Lotus. The early years, the Elite and origins of the Elan (If you have not read this, why not?) it says, on page 156-

"Chapman finally abandoned his "own" (note the inverted commas, PJT) Strut in the Elan application and reverted to a purely MacPherson Strut system in which the drive shaft was relieved of any lateral location duties. A wide-based welded tubular wishbone now performed this function but also largely absorbed the torque load from the outboard mounted disc brakes.
Because this was the first road-going application of the MacPherson strut principle to the rear suspension of a car, there was no proprietary hub casting available for adaptation and the elan is fitted with an Armstrong-made Strut spring/damper unit shrunk into a Lotus-designed alluminium casting carrying the ball races supporting the hub We may assume that the rear suspension of the elan is as it is for purely technical reasons. In the form used it is certainly no cheaper to manufacture than the Series Two Elite Chapman Strut. Whilst retaining the camber-control qualities of its predecessor it offers lower roll-centre as a result of the positive lateral location by a wishbone well below the hub centre height.Lateral loads on the backbone chassis-mounted differential unit no longer exist and the drive shaft is purely that, now being equipped with doughnut joints to absorb any slight misalignment during suspension movement".

Everything I have read about the "Chapman" strut always pointed out that the drive-shaft was a lateral load-bearing component of this system. So, why did the error creep into the Workshop Manual?

We can discuss the provenance of the strut another time.

[RogerFrench]

I don't think Robin Read was always right- he's certainly wrong to imply that the Elan was the first with struts at the rear - the type 14 Elite was surely the first?

As I remember things, and I'm old enough to remember them from the time they happened, and at that time was keen enough to take notice, the term "Chapman Strut" applied to the simple structure as first seen in the Lotus 12 single-seater and the type 14 Elite. This had three locating member; the fixed-length driveshaft, the strut, and a radius arm.
Subsequent renditions in the 15, 16 and 17, for example, replaced the radius arm with a wishbone, more like a MacPherson strut and removing the location responsibility from the driveshaft. They were still called "Chapman Struts" even then. This change was made because of the geometric imperfections of the original design, often one of Colin's failings.

It is my belief that some at Lotus still found it expedient to call them "Chapman Struts", though they had lost some of the lightness and simplicity of the earlier design, and continued to do so with the Elan. I don't think that Lotus used the term in their own Elan advertising, though I could easily be wrong about that. I remember them only calling it Strut suspension.

Edit Just had a thought - Chapman patented his strut; it might be interesting to see what the patent says and whether the Elan complies.

[elansprint71]

Roger,
I think you have mis-read my post; Read says "Chapman finally abandoned his "own" Strut in the Elan application..."

He details how, as you point out, the first car with the "Chapman" strut was the 12, after the designed-in de Dion unit failed to work and a hasty alternative had to be found.

The Elan non-steering MacPherson strut is nothing like the Chapman patent, which really is the point of this thread.

[stugilmour]

The Elan non-steering MacPherson strut is nothing like the Chapman patent, which really is the point of this thread.

So Pete, have you located the patent for the "Chapman Strut"?

I came across this while searching the 'net...

The Telgraph
By Brian Stater
12:01AM GMT 14 Dec 2002

Yet Chapman retains his devotees, even among those who know about his darker side. Graham Arnold, a Lotus sales director in the 1960s, remains convinced of Chapman's genius and is organising a complex search of files at the Patent Office to prove it. Arnold said: "Colin was without any doubt one of the finest engineers ever produced by this country. He's way up there in the company of Brunel.

"He had the most amazing, restless mind and he turned it to all sorts of problems. There was nothing that he felt was beyond him. For example, for a long period Colin had a painful condition with his ears and he's known to have filed patents, which I hope to retrieve, for devices which controlled the acceleration and deceleration of things like lifts and railway locomotives, where he always had discomfort."

So why might these "lost patents" prove difficult to find? Arnold laughs. "Because you can be sure they would have been filed in such a way they would prove of much greater benefit to Colin than the Inland Revenue."

[elansprint71]

The Elan non-steering MacPherson strut is nothing like the Chapman patent, which really is the point of this thread.

So Pete, have you located the patent for the "Chapman Strut"?

Actually my source was the same as yours, I had several long telephone conversations with Graham Arnold (probably around the time of the Telegraph piece) amongst other things one was about suspension design, another about Moonrakers and one about flying old aircraft. Arnold said that there had been confusion "in the press" over exactly what constituted the "Chapman" strut and he said that the unit used on the Twelve thro' to the Elite was and the unit on the Elan most definitely was not! He also alluded to the fact that the design had been cribbed from Gogomobile (who were rumoured to have stolen the design from Da Vinci!).

[GrUmPyBoDgEr]

The Elan non-steering MacPherson strut is nothing like the Chapman patent, which really is the point of this thread.

So Pete, have you located the patent for the "Chapman Strut"?

Actually my source was the same as yours, I had several long telephone conversations with Graham Arnold (probably around the time of the Telegraph piece) amongst other things one was about suspension design, another about Moonrakers and one about flying old aircraft. Arnold said that there had been confusion "in the press" over exactly what constituted the "Chapman" strut and he said that the unit used on the Twelve thro' to the Elite was and the unit on the Elan most definitely was not! He also alluded to the fact that the design had been cribbed from Gogomobile (who were rumoured to have stolen the design from Da Vinci!).

Karl Ludvigsen's mythbusting book "Colin Chapman--Inside the innovator"
Covers this subject quite well & shows that the "Chapman Strut" was cribbed from other car makers.
Assuming that to be the case; would Chapman/Lotus have been able to register the idea for patent?

I think that Da Vinci would feel quite proud about being credited with aspects of car designs; that really is visionary thinking

Cheers
John

[elansprint71]

Karl Ludvigsen's mythbusting book "Colin Chapman--Inside the innovator"
Covers this subject quite well & shows that the "Chapman Strut" was cribbed from other car makers.
Assuming that to be the case; would Chapman/Lotus have been able to register the idea for patent?

I think that Da Vinci would feel quite proud about being credited with aspects of car designs; that really is visionary thinking

Cheers
John

Reading what folks who were there at the time have said, the boss of Lotus seems to think that he could do whatever he wanted with other folks designs. Robin Read's book notes that Lotus had a "provisional patent" protecting the design. I'm not sure what that means.

I'm reasonably sure that Da Vinci used the strut design for the undercarriage of his steam-powered helicopter/wallpaper stripper.

[RogerFrench]

Roger,
I think you have mis-read my post; Read says "Chapman finally abandoned his "own" Strut in the Elan application..."

He details how, as you point out, the first car with the "Chapman" strut was the 12, after the designed-in de Dion unit failed to work and a hasty alternative had to be found.

The Elan non-steering MacPherson strut is nothing like the Chapman patent, which really is the point of this thread.

No, I didn't mis-read it, and in fact dug out my own copy of Read's book to see if he said anything pertinent elsewhere.

The point I'm getting at is that he'd already "abandoned his own Strut", some time before the Elan. Even in the Elite S2 the control problems had been recognised, and in 1959 Sixteen's rear suspension was pretty much like an Elan with a lower wishbone replacing the radius rod. Well, I suppose strictly speaking Len Terry abandoned it for him, since he did much of the work on those cars. But it was still, wrongly in my opinion, called a Chapman Strut. I agree with you, it's not like the original 1957 rendition, but is like the Elan.

The simple Goggomobil no doubt influenced the early design, but wasn't that swing-axle, with only one UJ in the halfshaft?

Oh, and by the way, "confusion in the press"? About things emanating from Lotus and Chapman? Surely not!

[elansprint71]

.........
The simple Goggomobil no doubt influenced the early design, but wasn't that swing-axle, with only one UJ in the halfshaft?

Oh, and by the way, "confusion in the press"? About things emanating from Lotus and Chapman? Surely not!

Yes- is it possible to have a more simple system? I think not.

Confusion: ?Confusion is a word we have invented for an order which is not yet understood?. Henry Miller.

I think that there was an unusual car back in the 30's, which had a rear engine, and huge coil-over struts not unlike the ones patented by our wayward genius. I'll have to rummage thro' books to find it because I can't remember the name.

[GrUmPyBoDgEr]

.........
The simple Goggomobil no doubt influenced the early design, but wasn't that swing-axle, with only one UJ in the halfshaft?

Oh, and by the way, "confusion in the press"? About things emanating from Lotus and Chapman? Surely not!

Yes- is it possible to have a more simple system? I think not.

Confusion: ?Confusion is a word we have invented for an order which is not yet understood?. Henry Miller.

I think that there was an unusual car back in the 30's, which had a rear engine, and huge coil-over struts not unlike the ones patented by our wayward genius. I'll have to rummage thro' books to find it because I can't remember the name.

You might be thinking of the 1932 Scarab, designed by William Stout?
Once again a swing axle design using a coil spring over dampers.
However from the sketch shown in Ludwigsen's book the dampers appear to have a pivot point where they attach via a rigid tubular extension to the swing axle & a wishbone attached at the lower end of the damper.
The 1957 Goggomobil certainly has the closest resemblance to the system used in the Mk14 Elite etc. but here again a swing axle with just 1 UJ on the inner ends of the drive shafts.

Cheers
John

[Peter Ross]

I have only just come across this thread, so apologise for the late comment.

I am glad that you eventually reached the right conclusion that the Elan does NOT have the Chapman Strut.

I also am glad that the truth about the Chapman patent was correctly stated. The Goggomobil design was not "stolen" by Chapman because it is a swing axle design, which the Chapman Strut most emphatically is not.

He details how, as you point out, the first car with the "Chapman" strut was the 12, after the designed-in de Dion unit failed to work and a hasty alternative had to be found.

I would like to take issue with this statement. The de Dion suspension on the first Lotus Twelve to run was by no means a failure, and was raced in that form and gained the only podium finish by a Twelve for a long time (mainly because it didn't have the dreaded "queerbox" and so was enabled actually to finish a race!).

Chapman produced both the de Dion and the Chapman Strut versions and let his drivers try them out and decide which was best. The Chapman Strut won.

I should know - I did the detail drawings for both installations.

Peter Ross

Editor of "Historic Lotus" magazine

[elansprint71]

I have only just come across this thread, so apologise for the late comment.

I am glad that you eventually reached the right conclusion that the Elan does NOT have the Chapman Strut.

I also am glad that the truth about the Chapman patent was correctly stated. The Goggomobil design was not "stolen" by Chapman because it is a swing axle design, which the Chapman Strut most emphatically is not.

He details how, as you point out, the first car with the "Chapman" strut was the 12, after the designed-in de Dion unit failed to work and a hasty alternative had to be found.

I would like to take issue with this statement. The de Dion suspension on the first Lotus Twelve to run was by no means a failure, and was raced in that form and gained the only podium finish by a Twelve for a long time (mainly because it didn't have the dreaded "queerbox" and so was enabled actually to finish a race!).

Chapman produced both the de Dion and the Chapman Strut versions and let his drivers try them out and decide which was best. The Chapman Strut won.

I should know - I did the detail drawings for both installations.

Peter Ross

Editor of "Historic Lotus" magazine

Peter- great to have you on here!
Can I give a plug to your superb book LOTUS THE EARLY YEARS.

This book is unlike many other Lotus books because it was written by someone who was there at the time, rather than someone who was not there at the time.

[RogerFrench]

Welcome indeed, and another plug for your book. It's great to have a voice of authority on a forum like this.

[garyeanderson]

I have only just come across this thread, so apologise for the late comment.

I am glad that you eventually reached the right conclusion that the Elan does NOT have the Chapman Strut.

I also am glad that the truth about the Chapman patent was correctly stated. The Goggomobil design was not "stolen" by Chapman because it is a swing axle design, which the Chapman Strut most emphatically is not.

He details how, as you point out, the first car with the "Chapman" strut was the 12, after the designed-in de Dion unit failed to work and a hasty alternative had to be found.

I would like to take issue with this statement. The de Dion suspension on the first Lotus Twelve to run was by no means a failure, and was raced in that form and gained the only podium finish by a Twelve for a long time (mainly because it didn't have the dreaded "queerbox" and so was enabled actually to finish a race!).

Chapman produced both the de Dion and the Chapman Strut versions and let his drivers try them out and decide which was best. The Chapman Strut won.

I should know - I did the detail drawings for both installations.

Peter Ross

Editor of "Historic Lotus" magazine

I took these two photos at Lime Rock probably sometime in the previous century, I don't recall what year but maybe 1995. I think its a Twelve, maybe the number helped me out a bit.

This one was in Brookline at the Museum of Transportation in 2001, I think I heard that it was less than real but it is still cool to look at. Parked next to the nineteen on the left is Russ Newtons Plus2. My S2 is next to Russ's Plus2 and Carl's red Elite is to the right of the nineteen.

Peter welcome to the forum

Gary

[Elan45]

Gary,
I think that is Gary Ford's 12. He used to run it at various VSCCA events. I have a series of photos I took at the Pittsburgh Vintage GP years ago. I haven't seen it lately.

Peter, Welcome to the forum. Always good to see someone cross over various older Lotus models. You will remember my ex-Keith Hall Eleven 4DTN.

Roger