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My one-off design


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#1 Wolf

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Posted 26 February 2012 - 20:08

OK ... <takes deep breath> ... I've finally decided to do something about the one-off car I've been dreaming of for ages. Being currently unemployed, it would seem as good a time as any to get properly started on the design. I hope it will be OK if I share

I've got the basic layout in my head, and to some extent on the 'puter, but here's the brief description. It will be rear (mid-)engined two seater with fiberglass sandwich monocoque tub (boat-style mouldless construction), additionally stiffened by 'stringers' and four Al box bulkheads (two will house all suspension components) bonded and bolted to the tub. The rest of it will basically be three fiberglass pieces- front and rear bodywork, and central section acting partly as bodywork, partly as stiffener, and partly as seats. Suspension will of course be double wishbones all around (general idea was pullrod at the front and pushrod to the upright at the rear). This design is partially necessitated by the cost, but because I will be able to work on design of various 'subassemblies' independently. BTW, I know I might be flamed by rather unorthodox (at least since 1960-ies) concept of using the driver's head to protect the car in case of flipping it over (rather than pansy vice-versa approach) but hey... even if I ever get to building one- it will be for personal use.

As for engine- it will have to be some motorcycle engine, although I might be more inclined to using 4AGE (but unfortunately, I think I'd have trouble laying my hands on one)...

Right now I'm putting together front suspension assembly, but am not terribly happy with suspension geometry so would welcome comments and criticisms (thankfully, my CAD model is quite adaptive, and I will be able to change anything, on the trot). I've managed quite decent scrub, more-or-less decent RCH, but I'm not so sure about camber change...Is anybody willing to help poor old moi?

My guesstimated values would suggest I would get around 50% load transfer ad 1.2g, which would result (without ARBs) in something like 1.5° roll... And here are some graphs I've made (I haven't done much in a way of placing steering rack and stuff):

Posted Image

P.S. As for RCH going bellow the ground, it might not be nicest thing to happen, but I reckon hitting the bump stops would already have unsettled the car before that...

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#2 Kelpiecross

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Posted 27 February 2012 - 03:11

[quote name='Wolf' date='Feb 27 2012, 07:08' post='5551852']

A sketch of the general layout and appearance of the car would be of interest.

"Boat-style mouldless" - what does this mean? I thought boats usually moulded?

No roll-over protection? Not a great idea I would have thought - and a roll bar can be used to strengthen the structure as well.

All the detail about the suspension characteristics seem to be a little premature.


#3 gruntguru

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Posted 27 February 2012 - 05:16

Suspension is usually a good place to start.

#4 cheapracer

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Posted 27 February 2012 - 05:52

Suspension is usually a good place to start.


Further to that wheels are the best place to start ie; wheel center heights, offsets and track.

Most start completely at the wrong end, the body and/or chassis.

And a critical question - what are you going to use it for Wolf and what do you expect it to do within that criteria?

Edited by cheapracer, 27 February 2012 - 05:53.


#5 Wolf

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Posted 27 February 2012 - 11:53

Ahhh, Cheapy the critical question... it will be a road car for personal use (I don't see it would be allowed to compete on anything but autoslalom, and I would think it unsuitable for such competitions), and I certainly don't see anybody crazy enough to buy something like that. And the expectations are to have it designed properly (or to the best of my abilities), not to fall apart, and hopefully be a quick little machine that would be fun to drive but still to require some skill to be properly driven. You know about that old 'passion' of mine <nudge, nudge, wink, wink>, and this should be a tribute of a sorts to it- a road going two-seater tribute to GPL (admittedly closer to '65 or advanced trainers than to proper cars).

Kelpiecross- I'll post a pic or two shortly (and the illustration of mouldless construction I had in mind)...

#6 Wolf

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Posted 27 February 2012 - 13:21

OK, prepare to be unimpressed... :lol: This is crude illustration of the basic layout without the windscreen. The second one is the aforementioned construction method, which was, to the best of my knowledge, so successfully demonstrated on Arnold AR-5 airplane (both in terms of success and achievable quality of the finish). The only difference will be that I think after the outer facesheet being laid and cured, I'll have to put inserts for bolts into the core before I lay the inner facesheet. And after that I'd see to it that the whole thing was vacuum-bagged and post-cured.

Cheapy, the tyres were a bit of a problem, so I decided to be pragmatic and see how I do with the rubber Elise has (on a car that's supposed to be smaller, lighter and faster than a 7)... And yes, I too did succumb to temptation of trying to style the thing concurrently with the design phase, but did not like it one bit. (and in case anybody's wondering why such a long wheelbase- it's sort of tailor made to fit myself in between the suspension boxes and the engine, and I'm a pretty lanky.)

Posted Image Posted Image

#7 Bloggsworth

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Posted 27 February 2012 - 22:07

Of the 3 major variables, and bearing in mind that you must choose 2 of 3, I would be more interested in the roll centre Vs C0fG movement - Radial tyres are relatively forgiving when it comes to camber change, as long as you don't choose stupidly shallow sidewalls. I would concentrate on reducing track change variation for better braking and acceleration, and a stable roll centre to maximise predictability in the handling - Just my opinion you understand.

Edited by Bloggsworth, 27 February 2012 - 22:11.


#8 Wolf

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Posted 27 February 2012 - 23:20

Thanks Bloggsworth, that's the kind of input I was hoping for... :up: BTW, I thought 2mm scrub in 90mm bump travel would be good enough (admittedly I have 1:10 in rebound, but I hoped that's fairly OK because of decreasing load). Tyres would be 55% profile- I would have liked skinnier ones, but I thought to go with Elise sizes (175/55 R16 front and 205/55 R17 rear).

As for RC vs CoG, I was going to post it for front and rear together, once I do rear suspension layout. (I figure the basic idea is to have them move 'parallel', to keep the lateral force couple the same through the whole range, right?) Incidentally, I had one 'variant' that seemed quite odd, I think it was quite short upper arm- with 25mm RCH at design position and never going below ground in 90mm bump. But it had rather small camber change (ISTR 1°), which made me think I'd have hard time making rear suspension to match (both for camber, which I think should be more 'positive' at the rear, and replicating the same RC to GoG characteristic)...

EDIT: I've finally ironed out some CAD problems I was having last few days, and am hoping I will have a pic (with most parts) of suspension layout I was having in mind... (oops, I still have to locate the pullrod rocker, hoping to get decent motion ratio and wheel to damper speed characteristic- that should keep me busy for a while :p)

Edited by Wolf, 27 February 2012 - 23:29.


#9 kikiturbo2

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Posted 28 February 2012 - 00:09

what is your target weight?... I thing you can get away with 15 inch wheels..

#10 Wolf

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Posted 28 February 2012 - 02:57

Yes, I think I could... and haven't ruled out that option (I'm no big fan of unsprung weight). As for target weight- man, that's a hard question.;) Maybe I'm a bit too optimistic- most my preliminary calculations are based on 500kg nominal load (wet weight with driver and fuel) at 350mm CoG height*... I have a feeling I could maybe manage 350kg dry weight with bike engine- so far, the main structure (tub with fiberglass stiffeners) should weigh no more than 25-30kg.

Sorry for the delay with the answer- first my model drove me crazy (everything was just fine until I put in rod ends, and suddenly everything got over-constrained), so I tackled pullrod linkage. I can't say I fared much better there either- initial layout gave me just about right numbers for a damper... until I calculated the spring rate: measly 22.5 N/mm. tskkk, tskkk

* first number is guesstimate, while other is even worse- I might've just pulled it out of a hat :lol:

#11 cheapracer

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Posted 28 February 2012 - 04:29

http://imageshack.us...71/ccgplyt.gif/


How you going to turn those front wheels?

I should mention mine has a similar taper in the area and I can refer you to here for those measurements and others that may be helpful...

http://www.locostusa.......=39&t=12756

If you go with a Toyota S series (5S, 3S, Camry, Celica, MR2 etc or 1MZ 3.0 V6) I can help you with a lot of layout items and including using a 4 link DeDion that 2 links running up either side would look appropriate for the period. Go for HiLux/HiAce/Previa/Tarago front uprights and brakes, bulletproof, low weight and removable steering arm.

Edited by cheapracer, 28 February 2012 - 04:41.


#12 mariner

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Posted 28 February 2012 - 04:59

I am sure you will get lots of good input on the suspension so may I just focus on the chassis. Your choice of boat composite construction is interesting because the first successful glass fibre racing car was the Chaparral where the chassis was built with help from an Andy Green , a Texas boat builder. So you are in good company.

Building in stresed GF is very tricky for several reasons

- Without molds and F1 style tooling the material can be dimensionally unstable so you could have a beautiful set of suspension points which don't happen in reality if the thing warps out of the mold. I am no expert ( I mess up GF regularly) but the craftmanship in terms of cure times etc is very important.

- The big structural problem is transferring loads from the metal suspension points into a GF skin as thin as possible. Some kind of bobbins are needed to distribute the load with local mat reinforcement. If you are using metal bulkheads then " crowsfeet" sheet metal load spreaders might work

- The fabrication of GF to a good standard is one thing designing it for adequate safety margins is much harder. Long ago Burt Rutan published a brilliant little "book" of instructions on making moldless planes. He stressed that amateur plane builders should be very wary of trying to design in GF themselves. His record in plane design suggests he knew what he was talking about.

- You are going to have to calculate a lot of loads to do really lightweight GF chassis which could be very long job.

Please ignore all the rambling above if you are , or have access to, GF design expertise.Also please don't take this as damning your project and ideas , go do it.

All a am saying is that the actual GF chassis stress analysis, design and high quality construction for safety may consume much more time than all the suspension/handling stuff

Good luck with it


#13 Engineguy

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Posted 28 February 2012 - 05:07

Posted Image

Wood Car

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#14 Bloggsworth

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Posted 28 February 2012 - 10:14

Low, fat tyres are all very aesthetic but not much fun to drive on on a public road. My MX5 came with 55 profile - They judder when turning sharply at parking speeds, are teeth rattling over potholes and are nowhere near as chuckable as the higher profile tyres on the older model. Squidgy sidewalls are an aid to lower speed sliding and more fun!

#15 Bloggsworth

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Posted 28 February 2012 - 10:21

I am sure you will get lots of good input on the suspension so may I just focus on the chassis. Your choice of boat composite construction is interesting because the first successful glass fibre racing car was the Chaparral where the chassis was built with help from an Andy Green , a Texas boat builder. So you are in good company.


Er - Have you forgotten the Lotus Elite Type 14 introduced in 1957 and in production from 1958,? A car raced with a great deal of success all over the world. It may be said that it was not designed solely as a racing car, but nothing Colin Chapman designed was not done so without at least half an eye on the possibility of racing. The Corvette, which preceeded both (1953), was a corporate marketing exercise and was designed for anything but racing.

#16 Wolf

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Posted 28 February 2012 - 10:52

Thanks guys, a lot of very useful input. :up:

Cheapy- good point... albeit, last time I checked I could turn the inside wheel by some 40°, which would suggest I may have widened body a bit in this pic- will have to recheck dimensions. Thnx for the link. :) I'll have a look if I can find relevant dimensions of those uprights, but if all else fails I don't think I'd have problem having my own two-piece Al uprights CNC'd (actually, just the other day I was at machine workshop a friend is working at, doing a bit of apprenticeship- just for fun of it, and hoping to learn a thing or two in the process).

Mariner, you raise few good points. As for fastening the bits to the GF, my intention was (as I may have mentioned) to use Al or steel inserts in the sandwich core- which will act as the crowfeet you mention but from inside of the material. I'm hoping to have a bit more dimensional stability on account of using cloth, rather than mat- and hopefully would err on the side of caution by using 5 layers of 7781 glass (8 harness satin, military spec material, IIRC strength in excess of 300MPa, or 45ksi) as each facesheet. Other aspect is that my design is to have all suspension hardpoints in Al box sections, which will then be glued to facesheets and bolted to those inserts- which would hopefully render all GF fabrication errors irrelevant and provide as accurate finished product as I could get.

#17 mariner

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Posted 28 February 2012 - 11:43

Bloggsworth, I thought about the Lotus Elite ( and one ot two other UK GF chassis cars) but my point was really to mention Andy Green being a boat builder. BTW the first Lotus Elites had such poor quality control when built at Maximar (?) that Lotus went to Bristol who knew more than a little about QC but reportedly lost money on every shell.

Wolf , I have read your comments about having the suspension hard points in the metal bulkheads and I understand the logic.

However , and I am NOT a GF expert, I do still think you may underestimate just how much GF can move around as it cures etc. It sounds like you are not building a msasive wall mold with temperature and humidity controlled cure and so I would suggest ( if I may ) that you have the facility to machine in ( or adjust) the suspension points after the shell is 100% complete. Maybe a two part bulkhead or something so you can measure any distortion and remove one part to drill the final mounting points.

I suspect that the tyre technology for the Lotus Elite era was less demanding of mounting precision than today's tyres.

I will stop labouring my point after saying that when I assembled a Marcos Mantula with GF body the longest assembly job was getting the electric windows to work properly simply because the motors and cranks were mounted on the GF door and nothing lined up. I had to make floating motor mounts to get reliable window operation!!

#18 Tony Matthews

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Posted 28 February 2012 - 12:16

when I assembled a Marcos Mantula with GF body the longest assembly job was getting the electric windows to work properly simply because the motors and cranks were mounted on the GF door and nothing lined up. I had to make floating motor mounts to get reliable window operation!!

It might be a good idea to bond in bobbins that are a) not pre-drilled and b) are of sufficient diametre that the final hole position can shift quite a way and still hit the bobbin!

Edited to say that bobbins are probably ancient technology, I think 'hard points' are more recent, and give a bit of latitude for hole placement. Don't be fooled into thinking I know what I'm talking about...

Edited by Tony Matthews, 28 February 2012 - 12:19.


#19 cheapracer

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Posted 28 February 2012 - 12:35

Thnx for the link. :) I'll have a look if I can find relevant dimensions of those uprights,


They are very strong but much lighter than they look and carry a decent sized vented disc with common 5 x 114.3 PCD.

From LocostUSA forum ...

KPI 9 degree
overall height 7 17/32"
steering arm length 5 9/16"
axle center to bottom of lower ball joint flange 1 5/8"
axle center to top of upper ball joint flange 6"
axle center to bottom of upper ball joint flange 5"
axle center to top of lower ball joint flange 3/4"
axle center and steering center are inline
steering arm is 3/4" lower than the top of the lower ball joint flange
outer tie rod end mounts on top of steering arm putting the center of tie rod higher than lower ball joint

Posted Image


Note the bolt on steering arms, that allows you options ...
Posted Image


As for RC vs CoG, I was going to post it for front and rear together, once I do rear suspension layout. (I figure the basic idea is to have them move 'parallel', to keep the lateral force couple the same through the whole range, right?) Incidentally, I had one 'variant' that seemed quite odd, I think it was quite short upper arm- with 25mm RCH at design position and never going below ground in 90mm bump. But it had rather small camber change (ISTR 1°), which made me think I'd have hard time making rear suspension to match (both for camber, which I think should be more 'positive' at the rear, and replicating the same RC to GoG characteristic)...


Forgot all about the hassles of compromised, guesstimated, black art of wobbly IFS, think I'll stick with my beams - oh my front RC is too low, I'll just take 3 minutes to undo that bolt and remove a spacer to raise it .....

Edited by cheapracer, 28 February 2012 - 12:53.


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#20 Wolf

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Posted 28 February 2012 - 13:08

Mariner- you *are not* labouring your point, and are actually very helpful and most constructive in your contribution. :up: And I certainly share your concerns, and would hate if I ended up with say left wheel 10mm in front of right wheel (and I wouldn't put something like that past me, if I didn't ensure right from design of the process that something like that cannot happen- and I'm far from being there ;)). :lol: In addition to 'blank inserts' big enough for build tolerances (to be drilled and tapped only at final stage of assembly), I was in a mind to use some sort of bolt-on subframe for assembly purposes- to assure that both front and rear suspension are as close to their intended positions and alignment as possible before I finalize the assembling process by drilling and tapping the holes in inserts.

Bloggsworth, you are certainly tempting me to revert to my original wishes to use higher profile tyres (and much narrower, too- I remember thinking I would like something like 145mm fronts and say 165mm rear tyres*, but was concerned with speed ratings and grip)... Hope you don't mind if I show my utter ignorance and ask a question or two on subject of tyres. Say, I have a Bridgestone tyre catalogue which lists stuff like tyre diameter, static loaded radius, &c. Is that SLR specified for rated load? the reason I'm asking is that I would like to incorporate tyre vertical stiffness into geometry calculatrions, and was hoping this would provide me with reasonably good guesstimate (albeit I'd still be at loss for inflation pressures, and their effect on stiffness and CP geometry**).

* to bring back the times as Fangio (or Froilan Gonzalez) has put it, when walking the F1 grid- 'In my time, tyres were skinny and drivers were fat." :p (oops, that would mean I'd have to put on a lot of weight for that to happen)

** oddly enough this seems rather underappreciated subject- off top of my head, I can recall only Foale's motorcycle book discussing the matter, and the tyre model that Greg had posted on his site

#21 Wolf

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Posted 28 February 2012 - 13:23

Tony, I'm glad to see we think alike on the subject. :)

Cheapy, you're a champ, posting that upright specs. :up: And speaking of beams and independent suspension, I've been wondering in recent time if anybody has ever tried some sort of 'hybrid' suspension. I would be tempted to see if some sort of 'frankensteinish' single lower wishbone (say, deDion type with sliding mount) with independent upper control arms could bring something to the table... (or would it bring out the worst in both designs and be a total and utter failure :lol:)

#22 cheapracer

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Posted 28 February 2012 - 14:05

And speaking of beams and independent suspension, I've been wondering in recent time if anybody has ever tried some sort of 'hybrid' suspension. I would be tempted to see if some sort of 'frankensteinish' single lower wishbone (say, deDion type with sliding mount) with independent upper control arms could bring something to the table...


Umm, you're not aware of my hybrid beam that's basically as you describe?

You might want to read this page .. http://forums.autosp...w...0&start=400

The big question is will you be using a seamless gearbox?



#23 Wolf

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Posted 28 February 2012 - 14:25

I'll have a seam right down the middle of diff casing, does that count? :lol: And speaking of diffs, I was thinking of being veeeery environmentally friendly and using a hybrid drive configuration... (will think about if I could pull it off, in case I use bike engine, to have alternative energy powered reverse 'gear'- probably an electric starter from a bigger car or some freakish flywheel design that will gear into the diff :lol:)

I've seen it, but was a bit 'under the weather' and couldn't figure out which link was doing what, so bookmarked it for later study. :up:

#24 kikiturbo2

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Posted 28 February 2012 - 14:39

Bloggsworth, you are certainly tempting me to revert to my original wishes to use higher profile tyres



for the record, my project has similar target weight, and is built around 175/55 R13, although tire choice currently made me have 185/60 for the start.. and I think that is plenty for such a light road car..

#25 Wolf

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Posted 28 February 2012 - 15:26

Thanks, Kikiturbo- will look into those alternatives. :) I'd almost forgotten that my idea of fun was to have more power than grip (like in the olden days of four-wheel drifts), and the sensible way to go about it is decent power and reducing grip... :D

As an aside, I'm a bit frustrated because I hoped to get same benefits from the pullrod arrangement as I hoped to have on that stillborn project I was working on. Back then I thought to have bended the regulations (partially for fun of it, but partially out of necessity), and came up with arrangement where I minimized loads from coil-overs fed into the chassis. Admittedly, most of the advantage would be lost by having rockers, but still- I'd feel a bit more pleased with myself (I'd say a bit smug) if I could 'replicate' that coil-over arrangement*.

* basically, I had them working 'against each other', with only a load resulting from load transferred from inner to outer wheel fed into the chassis (if there was no load transfer- no loads and no stresses on the chassis 'proper')

#26 kikiturbo2

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Posted 28 February 2012 - 16:01

well, if you had rockers, then that is where all those loads ended up going into the chasis.. :)

#27 Wolf

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Posted 28 February 2012 - 16:15

well, if you had rockers, then that is where all those loads ended up going into the chasis.. :)


Now I have them, but back then I didn't- just wishbones and coil-overs... :) I later spotted similar design on Pagani Zonda, but I was unaware of it at the time (and mine was multi-purpose, out of necessity- to allow more conventional coil-over placement at the rear)

#28 carlt

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Posted 28 February 2012 - 17:20

Just as an aside
This guy's previous Mini was called the Wolf [ Wolf in Sheeps clothing, I think it was Turbo Subaru Justy 4x4 floor pan ]
This new one has been christened the Bad Wolf
http://www.uphillrac...;highlight=wolf

Check out the posting dates from the start of the build to first test - pretty astonishing for a spare time build

#29 Kelpiecross

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Posted 29 February 2012 - 06:23

The big question is will you be using a seamless gearbox?


They are not really seamless you know.


#30 cheapracer

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Posted 29 February 2012 - 08:10

They are not really seamless you know.


Heresy, kill him till he's dead!


#31 Catalina Park

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Posted 29 February 2012 - 08:15

There has to be some sort of seam or you wouldn't be able to get the gears in the box.

#32 cheapracer

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Posted 29 February 2012 - 08:27

There has to be some sort of seam or you wouldn't be able to get the gears in the box.


Thats true although the "stumpy" Datsun Z20 box is close to seamless..

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#33 Catalina Park

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Posted 29 February 2012 - 08:58

Thats true although the "stumpy" Datsun Z20 box is close to seamless..


I had one of those in my LC Torana, god knows why!

#34 NeilR

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Posted 29 February 2012 - 09:16

As an owner of a fibreglass monocoque sportscar I would urge you to reconsider your choice of materials and go with a honeycomb panel. Why? Well consider that the laminate will lose a lot of it's structural performance with temperature - you need to consider this when choosing your resin. This will preclude polyester and make you consider vynalester or epoxy. Then look at available core materials and moulding costs etc. If you are going for core materials then you will not be using CSM, so some of the triaxial or multi-layer materials might be good.
Instead of continuing down this path have a look at the cut and fold Mosler chassis in the Super rod article. PM me if you want a copy - I think I have it somewhere.

#35 Tony Matthews

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Posted 29 February 2012 - 09:26

I'm not familiar with the Mosler chassis, but the origami technique worked well for Lotus for several seasons.

#36 GreenMachine

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Posted 29 February 2012 - 12:07

I'm not familiar with the Mosler chassis, but the origami technique worked well for Lotus for several seasons.


And Williams? IIRC, for a short period this technique was popular in F1.

#37 seldo

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Posted 29 February 2012 - 12:19

Forgot all about the hassles of compromised, guesstimated, black art of wobbly IFS, think I'll stick with my beams - oh my front RC is too low, I'll just take 3 minutes to undo that bolt and remove a spacer to raise it .....

Yep........:)

#38 cheapracer

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Posted 29 February 2012 - 12:55

I'm not familiar with the Mosler chassis, but the origami technique worked well for Lotus for several seasons.


Lotus use it today if you consider extruded aluminium is nothing but a folded profile as well as the basic box of the cabin.

On the other hand Ferrari, Bolwell, Lotus, Corvette are all very successful fibreglass cars.

This interesting chassis surprisingly is in my "interesting chassis" bookmarks ...

http://www.ffcars.co...ng-me-hand.html

This mob are just down the road from me but I wouldn't know where to start ..

http://www.chemshine.com/

#39 NeilR

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Posted 29 February 2012 - 13:31

No cheaply they are not in the sense of a composite structure. They are a steel chassis with a FG body. Different herring. I have no doubt that it can be done, he'll I followed this path for years and even spoke to Campbell Boswell about it and he went and built a car. I have a strong suspicion that you will spend more time, sweat and money to get something that will not perform as well as a conventional car. As far as suspension, I'd suggest using production components from the latest mx5 or the series 7 rx7

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#40 cheapracer

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Posted 29 February 2012 - 13:57

Fair enough, I didn't realise Wolf was considering a 100% FG car.

#41 Wolf

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Posted 29 February 2012 - 14:44

Thanks for the input guys. :up:

NeilR- so far I thought of it as only viable option. The structure I had in mind was very similar to a load bearing structure of a light production aircraft (Cirrus SR20), but with at least twice the cloth plies (for safety, damage tolerance*, and to account for possible manufacturing defects like poorer ply bonding, &c). I'm quite reluctant to give up on this point, but I will take your advice to heart, and consider it more carefully. :)

Cheapy, I intended it as FG being most, if not all, load bearing structure (not a FG body on a spaceframe). I'd use Al 'bulkheads'- two for suspension and two for additional bracing. Consider the structure like Lotus 25 chassis in FG sandwich with central section added (with 'fake' propshaft tunnel in the middle- not for propshaft, but as an additional 'top-hat' stiffener). Actually, my original wish was to have, just like 25, fuel-bags inside the tub, but everybody kept saying I was a lunatic and would never get it road-legal, so I chickened out of the idea... I'll try to post a pic later today to be clear about the idea.

* mind you, it was featured as an example in FAA overview of damage tolerance... (and I think they tested it for impact with hailstones- and they have 2 plies of fabric vs. 5 plies I'm intending to have)

EDIT: here's a 'similar' mouldless construction, but I'd have a hell of a hard time beating his record of 213knots with 65BHP- Arnold AR-5... :lol: Gorgeous little airplane (there are some construction pics on the site as well), but take a time and look at his more current F1 racer (AR-6) at the bottom of the page... looks absolutely stunning. :love:

Edited by Wolf, 29 February 2012 - 14:54.


#42 cheapracer

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Posted 29 February 2012 - 15:43

I like this chassis a lot, hope you get some ideas from it ...

Posted Image

#43 cheapracer

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Posted 29 February 2012 - 18:07

The Lotus Origami ...

Posted Image

#44 Wolf

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Posted 29 February 2012 - 18:44

And now for something completely anticlimact... oops, I meant different... :blush: 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.

Posted Image



#45 rachael

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Posted 29 February 2012 - 19:21

And now for something completely anticlimact... oops, I meant different... :blush: 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.

Posted Image


Nice! Those 'outer stiffeners' will boost the chassis torsional stiffness a huge amount!

#46 Tony Matthews

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Posted 29 February 2012 - 21:13

The Lotus Origami ...

Posted Image

Not what I was refering to, cheapy. I don't class extruded tubes as being folded. Is it possible to buy ready-made carbon/kevlar honeycomb or similar panels, as you could/can ali?

#47 NeilR

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Posted 29 February 2012 - 21:15

If you want to look back have a look at costins work with the Marcos cars. This is where chapman stole the idea for the lotus 25. It uses box sections as you show. The challenge is how to ensure structural integrity at the bond line. You could laminate over a large block of foam...have a look at the high end yacht hulls and the PVC closed cell foam core materials. Be warned that they are not cheap. The other alternative is to bond with a high end structural acrylic like the yachts. This it very much like my Rochdale Olympic. The real challenge is integrating the bulkheads and feeding in the suspension loads.
I suggest you also consider the repairability of the structure. Polyester is not nearly as good as epoxy in this regard. Vynalester somewhere between. Vynalester is more dimensionally stable and much tougher than poly, where the vibration from the engine etc will cause micro cracking and gradually soften the composite.

#48 carlt

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Posted 29 February 2012 - 21:31

This is where chapman stole the idea


Bloody hell ! I hope the Nostalgia Stassi dont see this - youll be strung up

#49 Wolf

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Posted 29 February 2012 - 21:54

Bloody hell ! I hope the Nostalgia Stassi dont see this - youll be strung up


Yep, I'm sure they never noticed that B.R.M. H-16 engine that was used in Lotus 48 (a year before DFV in 49) was designed as stressed chassis member, let alone front engined Lancia D.50 of 1954 (ISTR that Ferrari had put a small subframe around the engine when he purchased them- might've been for ease of maintenance, or he simply didn't trust the engine should be stressed member)...;) And that the first monocoque in Grand Prix racing was AFAIK La Voisine Laboratoire back in 1924 or 25... And I'm sure a search at TNF will produce picture or two of another invention commonly attributed to Chunky- Porsche on start of Nurburgring race in 1956, sporting a giant downforce producing wing mounted amidships (and the car, was, surprise, surprise- banned on safety grounds following a protest from official Porsche team... which BTW offered the man a job just after having him DQ-ed :lol:).

Thanks Rachael, and NeilR who has again spotted a thing that concerned me... :up:

P.S. the amazing story of Michael May, who made that winged Porsche doesn't nearly end there- later he raced in F1 (I think it was privately owned Lotus 18) against Ferrari cars whose engine he helped design (I'm not sure which of V6 engines they were running that year he was involved with... 60° or 120° one)

#50 NeilR

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Posted 29 February 2012 - 22:26

Bloody hell ! I hope the Nostalgia Stassi dont see this - youll be strung up

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...

Edited by NeilR, 29 February 2012 - 22:29.