32 replies to this topic

[mariner]

All the dicussions in the spaceframe thread about the gain in torsional rigidity realised when monocoques replaced spaceframes made me think again about something I have never really understood but which I assume FEA can now answer.

When the Lotus 25 monocoque was introduced Chapman was careful not to claim it as a full monocoque, rather he referred to it as two torsion boxes tied togeher by the bulkheads. That would suggest that in his mind it was clear that each torsion box twisted on its own and the stiffness came from two tubes each about 300mm*150mm. Sort of a big grown up twin tube chassis with very well designed bulkheads. So he was replacing a spaceframe which acted (poorly ) as a single torsion box with two much smaller boxes which worked much better so that the smaller total cross section out performed the single big "box".

When "full" monocoques came along the were seen as a one big tube , say 400mm*650mm but with a big weak hole in the middle to let the driver in. Nonetheless there were still side torsion boxes for fuel storage around the weak cockpit area.

Today the monocoques have very small side boxes as the fuel is all behind the driver and the cockpit area is kept narrow to allow big radiators and air flow etc.

I know that the carbon fibre is very strong and stiff but I cannot visualise the load paths, I would guess that the whole cockpit area twists as one big tube with the weakness of the regulation sized opening being overcome by very heavy reinforcement all around the opening edges ( as with an aircraft window design).


It may be a silly question but as cross section is the biggest single thing in getting torsional stiffness it just seems to me that the detail design which makes the chassis twist as one tube, and not two smaller l tubes either side of the driver is important.

Has anybody seen any FEA/visualisation on this?

[Greg Locock]

I know that the carbon fibre is very strong and stiff but I cannot visualise the load paths, I would guess that the whole cockpit area twists as one big tube with the weakness of the regulation sized opening being overcome by very heavy reinforcement all around the opening edges ( as with an aircraft window design).


It may be a silly question but as cross section is the biggest single thing in getting torsional stiffness it just seems to me that the detail design which makes the chassis twist as one tube, and not two smaller l tubes either side of the driver is important.

Has anybody seen any FEA/visualisation on this?

cross section is not the biggest factor. If you take a tube and twist it you get a stiffness k. Slit the same tube along its length and it will twist a hundred times as much for a given torque , if you let the ends move as they wish, with the same cross section. Even if you close the ends off with a bulkhead you still get an enormous(length dependent) reduction in stiffness.

So, the twin tube approach -or something more complex- is the only way of getting an open cockpit reasonably stiff without using a ludicrous amount of material. The Atom uses four tubes, as did many spaceframes. Their success or otherwise is dependent on how well they are tied together in front of and behind the driver. This is the big problem with the Lotus spine chassis-all the torsional stiffness was contributed by one rectangular box (I think it had some tubes in as well)- OK when 4000 was a good number, but embarassing when you wanted more.

The same actually occurs with tin tops, that's why A pillars look like fence posts and you bang your head when you get in the back seat(it's not just because you are drunk).

I'm sure some FSAEers have written papers on this.

Edited by Greg Locock, 22 September 2009 - 23:02.

[NRoshier]

The Lotus 25 was typical Chapman in that he found/adapted/borrowed an idea from somewhere else and used it in his cars. The idea was suggested to him by Frank Costin at the 1960 motorsport show, where Costin was showing his 'ugly duckling' plywood monocoque clubman style car made for Marcos. Costin said that Chapman told him that it would never work and Costin spent 15 minutes explaining that it was just two D Box sections tied together by bulkheads and that the practise was usual is aircraft....Costin having worked for Bristol. The Bristol connection goes deeper, because on the Rochdale Motor Panels stand was the Rochdale Olympic designed by a young Bristol trained engineer called Richard Parker. Costin spent some time inspecting the Olympic and offered Parker a job on the spot (at a substantial pay cut). The Olympic was a Fibreglass monocoque that was moulded in virtually one piece doing away with Chapman's idiosyncratic treatment of a FG monocoque with the Elite...which had an unfortunate reputation for falling to bits and almost sent Lotus broke. I spoke to Richard Parker about his experiences at Lotus at the time and he said it was a great place to learn and try things. He did not think much of Chapman as an engineer, but he was not as scathing as Len Terry. Parker said that Chapman had a real skill in motivating people, but he could be a real bastard the next day to the same person. Anyway I digress - Parker went to work one day and the racing team was standing around the first or second 25 monocoque looking unhappy as it had not performed as well as the 24 on the test rig. In short it was a flop. Parker related that none there had an aircraft background but him and he tentatively suggested that he might be able to help, with Chapman telling him to 'get on with it then'. After a week the issues were solved.
Much is made of Chapman's design prowess, but it is fair to say that he did not really design much in the way of whole cars after the 14, apart from the 30/40 sports cars which were not good. What Chapman had was a group of talented people behind the scenes such as Terry, Hickman, Parker etc who did the real engineering whilst Chapman set the overall direction...and claimed the credit. This latter part was certainly one of Chapman's personality foibles, but it also was good marketing in the sense that the 'aura' flowed across to the road cars...after all you could hardly read any road test of a Lotus that did not mention Chapman as a genius.
Current single seat cars do still have the 'twin tubes' in one sense in that there is two skins separated by honeycomb each side.

[dosco]

What Chapman had was a group of talented people behind the scenes such as Terry, Hickman, Parker etc who did the real engineering whilst Chapman set the overall direction...and claimed the credit.

It's good to be king.

Thanks for the info, though, very interesting.

[NRoshier]

You're welcome. I would honestly say that Ron Tauranac contributed more to racing car design than Chapman, though he is virtually unknown, which is a very unfortunate.

Edited by NRoshier, 23 September 2009 - 12:58.

[Tony Matthews]

Current single seat cars do still have the 'twin tubes' in one sense in that there is two skins separated by honeycomb each side.

Very interesting, NR, especially that last sentence, I hadn't thought of it in that way.

Edited by Tony Matthews, 23 September 2009 - 17:11.

[rms]

I would honestly say that Ron Tauranac contributed more to racing car design than Chapman

Any examples to back up such a rash statement ?

[McGuire]

Much is made of Chapman's design prowess, but it is fair to say that he did not really design much in the way of whole cars after the 14, apart from the 30/40 sports cars which were not good. What Chapman had was a group of talented people behind the scenes such as Terry, Hickman, Parker etc who did the real engineering whilst Chapman set the overall direction...and claimed the credit.

Where would any of them be without a Chapman?

[dosco]

Vary interesting, NR, especially that last sentence, I hadn't thought of it in that way.

Not sure that I think of it that way ... it makes about as much sense to me as saying a metal tube is "two tubes" due to the inner and outer surfaces being connected by the metal in between.

[DaveW]

Much is made of Chapman's design prowess.

Chapman life-style quote: "If you are driving in a queue of traffic, you are going the wrong way". Not always wise, but made for exciting times. I once asked PGW how he tolerated ACBC's interference. "He is often right" was the reply.

[NRoshier]

Any examples to back up such a rash statement ?

Actually yes, however by the tone of your response I suggest that you might be unaware of Ron's work over the 25 years he worked with Cooper, Brabham, RALT etc...certainly I am not fully conversant with it all as there is quite a lot.
However a few examples is what you were asking for: dry sump tank in bell housing between engine and transmission, uprights with shim adjustment so that camber could be changed very quickly without change in toe - a really clever idea if you think about it, transmission changes to lower engine below drive shafts, I am forgetting some others but I hope PatC will be along to add some more. Also recall how many cars Ron designed by himself over a long period and how competitive they were in all of the classes they ran in. Then add how very few injuries/deaths were attributed to his cars - which is not a comfortable comparison, but Ron certainly seemed to have a different perspective on this. You should also be aware that many later lotus cars used some Brabham components such as uprights - mind you the Brabham team would not hand over parts without cash coming the other way as according to many Chapman had a reputation for not paying his bills.
McGuire where would they be? Pretty much where they ended up I suspect. Chapman did not really boost others up into the limelight and these were also very talented engineers who post Lotus went on to have the successes they had, Terry in particular designed many cars for lots of different people.
Dosco the composite essentially makes a very stiff beam, which in some respects the D section alloy 25 side structure does - taking the loads around the cockpit. The materials and dimensions make the comparison a bit weak I admit, but how would you describe it?

Edited by NRoshier, 23 September 2009 - 22:52.

[rms]

Actually yes, however by the tone of your response I suggest that you might be unaware of Ron's work over the 25 years he worked with Cooper, Brabham, RALT etc

Another rash statement !

While the forementioned designs are very worthwhile, I would not rank them as ground breaking.
Ron is a very down to earth engineer and a good business man, and from what I have heard from people directly involved, every bit as dictatorial as Chapman when the need arose. After all, he was the boss, as was Chapman.

[Joe Bosworth]

As a past owner of a Team Lotus Lotus and a long term owner of a near team Brabham BT15 and a bit of a close watcher of both in their primes let me throw in my insight.

They were two totally different designers.

Chapman was a big picture innovator who over a long time came up with a large number of break through brilliant broad concepts.

Tauranac made his place by doing a brilliant job of taking common and simple conncepts and adding innovative detail and honing the concepts to perfection.

There is no better examples than my cars. Over several seasons with the Lotus I had to make a few running welded repairs and beef-ups that once fixed were reliable. Seven years after construction it was still able to set a lap record.

The Brabham never had a break despite taking some unholy bangs, one of which saw a Lola loose both its wheels on one side and the Brabham never need even re-adjusting. The Lotus was a bitch for access to work on while the Brabham could be easily stripped with only about two sizes of wrenches in your pocket.

Chunky was the one of the worldś best innovators but weak on detail. Ron was one of the worldś best detail guys. Quite different minds but similar in personalities.

Regards

[NRoshier]

rms I'm quite prepared to accept the latter, but not the former was rash, but his is the danger of the www I do not know you nor you know me.
As far as ground breaking...it depends on what you consider ground breaking. I think the upright was simply genius for this reason: you have X amount of time for practice at a track with an essentially unproven car. It goes out and does 5 laps and driver comes into the pits and wants more camber. Loosen off bolts, change numbered shim, tighten bolts and driver is out again in less than one minute with some heat in tyres. Out lap means tyres are up to temp, does three more laps and another adjustment...no toe changes etc. This means the car can be optimised very quickly with minimal cost/effort. The alternative upright design means, wheels off, unbolt rose joint, adjust rose joint, reattach and then adjust toe and then wheels on and out...on cold tyres etc. I personally think that it is these details that would often make the difference in a weekends racing.
I appreciate your insight Joe and agree with most of "Chunky was the one of the worldś best innovators but weak on detail. Ron was one of the worldś best detail guys. Quite different minds but similar in personalities." except the last part. I cannot compare personalities having never met Chapman and do not want to judge Ron by the limited meetings I have had with him. There seems to be two broad camps of thought on Chapman: the first is that he was a genius who was unfortunate not to do a lot better, the second is that he was bright but had many flaws and I perhaps lean more towards the latter. Joe which brand car would you prefer to drive or manage for someone else?
I'm interested to find out which broad concepts did Chapman really innovate by himself, especially ones that continued/were successful? Wings: we all know of Chapparal - were they before Lotus?, also was not ground effects also in Can-Am with McLaren? The tunnel cars and sliding skirts etc...this was Chapman's idea or the aero guys in Lotus?

[Greg Locock]

If you imagine a C section with the middle hollowed out, so it is two concentric skins with endplates, in corss section, its torsional resistance will be better than a single skin, but still rubbish compared with a tube. If you then add a shear web between the inner skin and the outer, it'll be better again, but still rubbish compared with a tube. If you look at the shear flow around these slotted section what you get is that the return flow round the inside skin CANCELS a large part of the flow around the outside skin. In comparison the shear flow in a tube all points the same way.

Ths is all nice linear stuff and is one area where FEA really helps, as there is not a good reliable accuarte manual method for estimating the torsional resistance of general thin wall sections with re-entrant profiles, etc.

[Joe Bosworth]

Rosh

On the issue of Chunky's personality I can make some comment as my ownership of one of his personal cars for several years allowed me to make small talk with him on the odd occesion. But these odd occasions let me strongly recommend that you read Peter Ross's book, "Lotus the Early Years".

Peter was a contemporary of Chapman and his book captures the flavour very well. My history with the Lotus has also caused me to have communications with Peter that pretty well adds insights. Peter also lurks around these pages on the odd occasions. I won't add further on the subject but do encourage the reading of his book.

As to who did what in technology first is fraught with arguement, some of which has been carried out over years on TNF. No sense on re-hashing here. But Chapman was unparalled for many years in glueing bits and pieces into broad concepts. He really did wonders in developing space frames in conjunction with what were modern suspension concepts such as soft springs and firm shocks along with minimising unsprung weight. His whole play on downforce was at the cutting edge and arguably leading.

As to which type of car would I prefer to drive or manage (customer cars) is differing in points of time. In the years 1953/4ish to say about 1963 the answer foe me is an unwavering statement of pro-Lotus.

By 1964/5 the answer is just as un-wavering a pro-Brabham. The BT15 F3 car was a hands down worlds best and other Brabham models such as the BT8 similar.

Regards

[NRoshier]

I believe I have a copy of Ross' book, I'll try to dig it out and have another read. I am not disagreeing with your opinion of the worth of the book, but I am always wary of a single perspective account of a personality. Of course the issue with researching say Chapman now is that we would be relying on the recollections of people (by this I mean those who worked with Chapman though his early and late years) which as with wine, can become affected by years passing- either to the detriment or benefit of the individual (the old 'hell it wasn't so bad"). From reading Costin and Phipps and in speaking to some local Lola owners I have developed a high regard for Eric Broadley - his chassis work seems somewhat superior to the equivalent Lotus cars. I do agree that Chapman pushed the space frame design in his early years and in some respects his early work established his reputation, which some of his later work would not have done.
I think Richard Parkers work on the Lotus 25 may have been in correctly stressing the 25 tub and also in feeding the loads into it. Sadly he passed away from Leukaemia about 3-4 years ago, having updated a Rochdale Olympic to a modern spec with a V6 Cosworth engine.

Edited by NRoshier, 24 September 2009 - 10:47.

[Pat Clarke]

Quote NeilR "I am forgetting some others but I hope PatC will be along to add some more."

There are lots more Neil, but getting involved in a debate like this is rather pointless. ACBC and RonT are/were different, (though similar).

Personally, I loved Lotus from seeing my first Mk6 through to the Jimmy Clark era, though when I was mature/educated enough to tell the difference, I far preferred RonT's way of doing things. Safe, simple cars that one could win with.

Retrospectoion being what it is, I recall casually accepting stuff like the 18 whilst actually looking at it's shortcomings without seeing them. Now I hate cars like that!

Cheers

Pat

[Powersteer]

Chapman was an automotive engineering philosopher.

[NRoshier]

Fair enough Pat, I did not want a debate of who was 'best' rather a discussion of their works. The foundation of this is a discussion with friends, one of whom I am assisting (in a minor way) in the design of his new sports sedan. In this discussion the origin of some design elements was discussed and some, such as the upright design, were attributable to RonT - thus these developments are enduring. Not knowing the full oeuvre of ACBC's works I am perhaps missing his contribution.

[cheapracer]

Lotus 25...




and a recent FSAE chassis that I dig...

[pugfan]

Lotus 25...




and a recent FSAE chassis that I dig...

Nifty, are those carbon fibre tubes and shear panels?

[Joe Bosworth]

Cheapy

That´s very interesting.

How heavy and how stiff??

Regards

[cheapracer]

Cheapy

That´s very interesting.

How heavy and how stiff??

Regards

Thats a bit personal isn't it?

Oh, you mean the chassis, hmm when I have a moment later I'll try to dig up the website ....

Nifty, are those carbon fibre tubes and shear panels?

I think it's a one off, I don't think they are sharing the panels with anybody.

Edited by cheapracer, 25 September 2009 - 05:23.

[gruntguru]

I think it's a one off, I don't think they are sharing the panels with anybody.

Shear panels dummy - where they put the sheep.

[jeremy durward]

Shear panels dummy - where they put the sheep.

and then they use those rocket launcher tubes to launch the sheep right?

[cheapracer]

Ahh here it is, easy to find when you type in 600cc V8 engine, feel a bit annoyed about it actually - on one hand it's great to see high tech within a class, sure, but I feel sorry for the underbudget Uni's who can't match that sort of stuff. I don't think theres anything special about what they have done (I do like the chassis design though) except to spend big money.

I think there should be brains/innovation via a money budget, maybe they need a bucket class as well (please excuse me if they already do).

http://dot.etec.wwu....fsae/index.html

Oh thats the old website, if you wait you will be redirected which isn't what you want because the 'Viking XXXV' link has lots of good tech pictures.

New website.,.,
http://www.wwufsae.com/

Check out "home" > "archives"

movie for the other lazy people like me..
http://westernfronto...ormula-sae-car/

Edited by cheapracer, 25 September 2009 - 12:09.

[GeorgeTheCar]

I looked at the Lotus 78 Wikipedia entry only to be stunned by the following statement, "

It had a slimmer, stronger monocoque cast in aluminium,[citation needed] which was developed from the 77." Must have been cast with the Cosworth thin-wall technology!

I have never heard of a cast monocoque. I am quite prepared to note that the bulkheads may have been cast but the whole monocoque? Never

Comments?

Edited by GeorgeTheCar, 25 September 2009 - 15:09.

[Tony Matthews]

Lotus 78 Wikipedia entry

It had a slimmer, stronger monocoque cast in aluminium,[citation needed] which was developed from the 77." Must have been cast with the Cosworth thin-wall technology!

Copyright Tony Matthews. Obviously cast, as you can see!

[cheapracer]

Must have been cast with the Cosworth thin-wall technology!



Comments?

Don't crash.



Oh the red cross Lotus hey Tony!
ahh, China's hard to take sometimes, if it wasn't for the easy life, the woman, the easy life, the woman, the easy life, oh and also the woman, i wouldn't stay.

Edited by cheapracer, 25 September 2009 - 16:26.

[Tony Matthews]

Just for you, Cheapy...X,X and X

OT, your lady has lovely eyes!

[macoran]

1967 F1 Eagle monocoque sketches by Brian Hatton for your scrutiny.

[V8 Fireworks]

I think there should be brains/innovation via a money budget, maybe they need a bucket class as well (please excuse me if they already do).

As many points for presentation and report (cost analysis etc) events as for driving the car events aren't there?

Of course teams with simple spaceframe/motorcycle engine car with flawless mechanical design and best implementation they could afford, complain that whizz-bang cars with fancy features and unlimited manufacturing resources to accomplish such are favoured in the awarding of design points.....

In attending, Ross Brawn remarked that "weekend autocross racers" (the design objective) are unlikely to be thrilled at the complexity to operate and repair the whizz-bang cars did he not stating that those guys and girls had rather missed the point?!

Edited by V8 Fireworks, 26 September 2009 - 00:05.