My one-off design

I'm a bit fuzzy with history Neil- which Costin was involved with Marcos? I seem to recall there were two brothers (Mike and Frank)... I would bet the Marcos one was the one that was previously involved with Chapman on Vanwall redesign, and did aerodynamic bodies for Lotus cars (and later wrote the chassis book), not the Cosworth one, am I right?

Edited by Wolf, 29 February 2012 - 22:38.

Wolf, for a one off, build a steel spaceframe, wear the 5kg (shock-horror) weight penalty and invest the hundreds (thousands?) of hours saved elsewhere - perhaps driving your toy. Just my $0.02. (I am a lazy bastard.)

Wolf, for a one off, build a steel spaceframe, wear the 5kg (shock-horror) weight penalty and invest the hundreds (thousands?) of hours saved elsewhere - perhaps driving your toy. Just my $0.02. (I am a lazy bastard.)

+100 on that..

Denis Palatov did a one off composite frame for his D1, then returned to steel spaceframe for production..

Wolf, frank was the aerodynamicist and mike the engine guy. Frank wrote a book called (I think) flying on four wheels. He did not care for aesthetics, but he did work for Marcos with the wooden cars, the costin Nathan cars and the costin amigo. You can find the details of each on line. He was a very clever engineer of the old school...I.e. you do all the calculations yourself. I personally rate Eric Broadley and frank above chapman (note I do not say lotus).
Nostalgia is itself part of the problem in judging the past. The rosy glow of times past can colour our perceptions of reality, like the mini driver who quite rightly recalls the chuck ability, sharp handling and delight of a country drive, but forgets the rust, the oil leaks, the poor starting when cold and wet and the dodgy build quality...I am as guilty of this any anyone btw!

Why do you guys think once (if ever) I start the project that this tub wouldn't be one of the least labour- and time- consuming parts? I would venture a guess above pictured tub could be done, from ground up, in less than a week...

As for D1, I remember seeing his site when he was working on prototype, spending a huge amount of money on that carbon bodyshell and putting it on steel spaceframe.. and I couldn't help (however I liked his project) that he was doing it the other way around- I'd feel the expenditure would be justified if he put the carbon in well engineered monocoque*, and did the cost-savings with some flimsy bodywork, probably in GF...

* unlike mine, let us be clear- I'm aware I'm more or less clueless about loads and load paths such design would be subject to... so I opted for rather agricultural (but hopefully, engineering wise, sound) structure and compensated with safety margin...

Yes, you are correct Neil- but the book I was thinking of is great little gem called "Racing & Sports Car Chassis Design" from 1965 and was apparently written by the other brother, Mike (I could hardly imagine third Costin suddenly springing up, haha)*... Maybe Frank didn't care much for aesthetics, but his Vanwall and little Lotus cars looked great (I semm to recall he started as early as Mk VIII or IX).

* the reason I asked is that there seems to be no mention of Marcos when discussing monocoque tub of Lotus 25...;)

Why do you guys think once (if ever) I start the project that this tub wouldn't be one of the least labour- and time- consuming parts? I would venture a guess above pictured tub could be done, from ground up, in less than a week...

Being unfamiliar with composite construction, I just see it as all very difficult. I take my hat off to you and wish you every success with the project.

Yep, Costin and Phipps did the book you mention and it has yet to be surpassed IMO.
Yes, Costin any of the other Lotus engineers get any mention, but that was part of Chapman's branding efforts with Lotus, following in the footsteps of Ferrari et al.
I have no doubt you can make the tub and make it work. I strongly urge you to forget about thinking of weight as an issue and allowing for a 200% safety factor, after all it will be your life in this car. Also you must become familiar with the materials long before you attempt the car. I am familiar with vacuum bagging and wet layup and I would consider this a very big job. There are some very good tutorials on youtube re layup and resin infusion. Be aware that the resin and the cloth will be less than 50% of the cost once you add vacuum pump, breather cloth, peelply etc etc. Also check out the various core materials. Here I'd suggest you forget the foams and just use one of the thick coremat materials. It will be much easier to use, tougher and easier to repair. Huntsman do a good one that has a hexagonal resin bled through. There are also some that are better structurally, but I have not used them.
I'd also suggest that you think 'boat' and not 'plane' when looking at the construction methods - they are closer to the operating issues of a car.

Wolf, frank was the aerodynamicist and mike the engine guy. Frank wrote a book called (I think) flying on four wheels. He did not care for aesthetics, but he did work for Marcos with the wooden cars, the costin Nathan cars and the costin amigo. You can find the details of each on line. He was a very clever engineer of the old school...I.e. you do all the calculations yourself. I personally rate Eric Broadley and frank above chapman (note I do not say lotus).
Nostalgia is itself part of the problem in judging the past. The rosy glow of times past can colour our perceptions of reality, like the mini driver who quite rightly recalls the chuck ability, sharp handling and delight of a country drive, but forgets the rust, the oil leaks, the poor starting when cold and wet and the dodgy build quality...I am as guilty of this any anyone btw!

Thanks, Gruntguru- but I'm not saying you're wrong... just that I hope you are. I may be miles off in my estimation, but I figured that will all this fancy technology today one could plan and prepare for composite layup well in advance, and that when it came to building it would be matter of cutting the fabric in predefined pattern, impregnating them (I wouldn't like to use conventional wet lay-up so that I can better control resin to fiber ratio... but am designing for worst possible ratio) and laying them up.

As an aside, I do not recall seeing many (riveted) aluminium stressed skin builds- any speculation why? I'd think it could be a nice, and relatively interesting build... (and am I wrong in thinking Osella or some company like that still makes competition cars with this technology?)

Speaking off-topic, and unusual projects... I've picked up this pic somewhere (might be even TNF) but for life of me can't remember what it's supposed to be... Any clues?

EDIT: Neil, thanks for advice. And I think I may have seen adhesive films used between GF fabric and Al honeycomb, but I'd think that technology would be way over my head...

Edited by Wolf, 01 March 2012 - 00:36.

adhesive films are heat activated, usually at around 110-130 degress C, which means you would need a method of heating the composite - panels are done in a steam heated plattern press. You can get tape adhesives that are made by the 3M company. They are epoxies as well as others, but I have no experience with them and they were expensive when I looked - but you are in a different market.
Have a look for images and details of the westfield FW400, which is a wetlayup clubman chassis.
also have a look at: http://alexandria.tu...ooks/627108.pdf
If you are looking at Resin infusion then you will need to ensure that you get infusion suitable resins/cloth, which will alter the mechanical performance somewhat. You will also need to change the materials you are going to use and I'd suggest you budget for at least one failure - it is a big part to infuse given you have no experience. So find someone who has done this...again I'd suggest you see if there is a dinghy maker of canoe maker doing this loaclly near you. Forget 'ideal' resin to cloth ratio...you will be 10% over even with infusion. It takes practice and experience with a part to get close to 'ideal'.

Heh, I'd give this thread a five star rating, but can't for fear somebody might erroneously think I've given it for my contributions...

I'm definitely in wrong market for high tech stuff- the idea was wet(ish) layup on Divinycel core, with a hope of vacuum-bagged post cure, but I'll reconsider the latter part on your assessment that it will skyrocket the costs... If I wouldn't need molds for post-cure, maybe I could find a serious boatbuilder with autoclave (and I think I've heard of one, not far from me) and pay for it. I'm not all too fond of the baking, but I understand that it considerably helps with consolidation of the material.

Wolf, you must have what it takes.. we are all telling you a sressed GF chassis is a big deal and you still want to do it.. way to go.

May I suggest an alternative fabriction technique that will get you your three box layout as long as you limit yourself to two dimensional curves .

Reverse the high tech honeycomb approach and build it in GF skinned marine ply. This is , perhaps, the 21 st century update on the Costin wooden Marcos chassis.

You can build a trial chassis in just ply quite easily and cheaply. The panels can be joined by edge gluing or that plus triangular fillets ( as was the Macros chassis)

Slots and dovetails would lock the panels together wherever possible for rigidity.

Plywood is , to quote Frank Costin " god's composite"


All the sub frame work and general layout can be done just with the plywood only version. External jigging points can be created around it if needed.

If you are careful some degree of 3D curve is possible by twisting the 2d curve panels along their length - I think your proposed chassis could be done like that.

Once you have got your " prototype" you can do a second one where you lay up the GF cloth onto the plywood to get the full strength. I have not done this so I am TOOMA but you could probably vacuum bag most panels individually for speed and QC then screw and bond them together using the slot and dovetail technique for accuracy and strength. . Large box sections would be strong enough to survive a total vacuum wrap for the outer skin without collapsing.

I can sort of see that this might work and low-ish cost and fabrication risk - the trick would be to plan th assembly sequence carefully to allow final assembly

Mariner, I'm arguing my point of why and how I was hoping to build it... You all point out what you think are, or might be, errors in concept or troubles you predict I will encounter during fabrication- and I do appreciate that. I mean, it's sort of things I started this thread for- it's not meant to be "look, I'm so clever and you're all fools for not coming up with something like that before I did", but to draw many varied opinions and experience of others. Only because I 'defend' my original idea/design in this early stage, doesn't mean I'll stubbornly stick to it regardless of good advice I receive here (just that I'm still not fully prepared to give it up yet... not without a fight ). I would hate it if somebody would think I do not genuinely appreciate every advice, criticism or input I receive here...

But if I was to 'limit myself' to 2D curvature as you suggest, I would consider abandoning stressed GF concept entirely... I think it would make more sense to buy a handbrake and use sheet aluminium. Riveting 'few panels' together would seem to be much less hassle, and would produce more predictable, consistent and 'usable' result (no worries on quality of layup, how I'm going to attach things to it, &c). That's why I raised the issue few posts back- if I will have backup plan, that's sort of thing I'd be most inclined to. IIANM this technology was predominant in '70ies F1, and I certainly do not consider myself capable of producing anything faster or better than that. And it would certainly present interesting design challenge.

Speaking off-topic, and unusual projects... I've picked up this pic somewhere (might be even TNF) but for life of me can't remember what it's supposed to be... Any clues?

1972 AAR Eagle Indy racer someone drew fenders on?

Wolf shoot me an email and I'll send the super rod article, it may change your mind on what you want to do.
Alloy folded tubs are hard to do, much harder than the composite for me as I have limited alloy fabrication skills. You can simplify the chassis with the use of panels. Look for images of the XJ 220 chassis. This uses two longitudinal beams of 50mm thick honecomb panel with a panel floor and bulkheads - it is very simple.

I wrote this at LocostUSA recently ...

I've actually decided against aluminium, it's so easy to get so excited about a new concept that you only see the benefits - I've had a few days thinking about it and it goes against some of my beliefs about aftersales affordability such as crash repairs, what are you going to do with a bent aluminium chassis?

Imagine if aluminium was the mainstream and that's what we all had - one day someone comes along and says "I want to introduce a new radical product I call "steel", when engineered properly it weighs hardly any more, any handyman can fabricate it or repair in their backyard shed with ease, lasts twice as long as aluminium, easier to paint and very strong!"

This new "steel" would be the weapon of choice for all of us and we would be saying "Why did we ever bother with that aluminium...".

Speaking off-topic, and unusual projects... I've picked up this pic somewhere (might be even TNF) but for life of me can't remember what it's supposed to be... Any clues?

I would suggest a concept Eagle Indycar modded for Can Am's later 1980's single seat era.

Wolf, for a one off, build a steel spaceframe, wear the 5kg (shock-horror) weight penalty and invest the hundreds (thousands?) of hours saved elsewhere - perhaps driving your toy. Just my $0.02. (I am a lazy bastard.)

Wolfy - I have to agree totally with The Grunt (something which doesn't always happen). I must be one of the few people who have actually completed (at least to the putting in engine and drivetrain stage) a stressed fibreglass monocoque chassis/body with spaceframe "upperworks". I decided to start on the fibreglass bit first - I would be embarrassed (literally) to say just how many years it took me to complete it - and then I only managed to get it finished because my eldest son had grown up enough to help me. It is an enormous amount of work. Endless sanding, laminating etc. I recall reading in RaceTech magazine (or some similar publication) that the typical time for an amateur to build a fibreglass body from scratch basically singlehanded was at least five years - I would have to say that this would be a minimum. This "mouldless" construction is probably quicker - but I imagine still a lot of work.

On the other hand when I finally started on the spaceframe and steel sheet bulkhead bits - I was amazed how quickly it all progressed. The spaceframe etc. took a matter of weeks of part-time work - the fibreglass many years.

If I had my time over (and generally speaking, that doesn't happen) I would follow the spaceframe/folded metal path - not bloody fibreglass.

And now for something completely anticlimact... oops, I meant different... You've forced my hand a bit, wishing to show my idea I wasn't as orderly as I would normally be when modeling. (and seeing how those stiffeners would run up to Al suspension boxes I'll probably fasten them to those as well (but haven't modeled it yet). Hopefully, you'll get the gist of the idea to see whether it will be adequate for the purpose or not... Outer stiffeners run from front to rear suspension box, and the middle one up to the second 'bulkhead', with the first one will be approx. half way on it (it will form a front part of cockpit, while the rear one will have seatbelts and probably engine mounted on it)...

Opinions and criticisms are welcome.

You really like to make things dificult for yourself don't you, have fun folding the flanges on the curved panels! I am assuming that this is going to be an aluminium structure. Its torsional stiffness will be a function of the bulkheads, and the centre rib won't contribute much unless it is tied in to the sides properly. If it is GRP it will be as stiff as wet pasta.

Edited by Bloggsworth, 01 March 2012 - 19:20.

Wolf - Do you want to start a new thread on the suspension kinematics?

Thanks for the suggestion, Greg- I might as well do... but pls. give me a day or two to come up with starting idea for the discussion (once I got the tyre spring built in the model, the point where RCH got below ground came uncomfortably close to equivalent of 2g vertical load. Moreover, this thread got me wondering about chassis layout, which might remove some unnecessary constraints on suspension layout*).

Bloggsworth- it was meant to be GRP (even I wouldn't be crazy enough to try to do it in Al), but I think the parts not shown (2 Al bulkheads, plus already mentioned stiffening section of bodywork which was to interlink all tub components with one of the bulkheads) would presumably stiffen the tub enough by making all sections work together... It may look flimsy as depicted, hanging together glued in few strips, but you'll have to trust me that I did pay attention to the way it was supposed to be stiffened (mind you, even though I've almost given up on this concept, I may yet devote a day or two to modeling it, just to show how I intended to make it work... but not right now).

* I had to raise inner pivots of lower wishbones because I didn't like the idea of having them 'cut into' the flat section of the tub... with that gone, maybe there's a bit room for improvement (horizontal lower wishbone at design position, and a bit lowered lower outer BJ)

Meh! They can kiss my bahookie!
Nostalgia is what their view of chapman is, not history or truth. Costin is on record for sharing the moment at the Motorsport show when he discussed the 'ugly duckling' Marcos with chapman and explained to chapman how the chassis worked, chapman was dismissive of it, thinking that it would not work. Costin was an aircraft engineer and so the stressed D box sections that made up the monocoque were standard fare to him. Who do you believe? I believe costin, he was a man that did not suffer fools gladly and he frankly did not care what others thought, whereas chapman groomed the press and was the figurehead of lotus, taking credit for the work of many other, more capable than him, engineers. Was he a significant figure in Motorsport absolutely. Did he have some good ideas, absolutely. Did he personally design anything of significance after the lotus 14? He came up with broad ideas and then instructed others to make them work...

Sounds just like Steve Jobs...