NEW CAV MONOCOQUE VS OLDER ERA?
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Jim Rosenthal
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Malcolm,
We are in the final stages of the deal. I have ordered the body; I will post details once the agreements are to everyone's satisfaction, which I expect (hope) will be soon. Thanks for your interest, watch this space for further details.
Jim R
We are in the final stages of the deal. I have ordered the body; I will post details once the agreements are to everyone's satisfaction, which I expect (hope) will be soon. Thanks for your interest, watch this space for further details.
Jim R
I have read that the Mk IV or "J-car" was not a welded monocoque construction, but rather an aluminum honeycomb sandwiched together and held by glue with all bracketry glued on as well. Does anyone know any more details of this type of construction such as type of adhesive used, cross sectional dimensions, photographs or drawings, etc. Further, why isn't this type of construction being considered by the replica manufacturers? It appears that the 2002 FoMoCo GT40 Concept Car uses adhesives rather than welding in the aluminum space frame chassis, and I am thinking about gluing the motor into my car but I'm not sure if the tile cement I have left over from my last bathroom job will be adequate. Seriously, any technical info on this subject would be appreciated.
Regards,
Blue
Regards,
Blue
The MK4 was built mostly from 1" honeycomb.
Lots of glue (I think it was epoxy back then) and rivets.
It looks like in many places the glue was more important than the rivets. It makes sense, considering that the honeyco.mb skin was probably only about 0.025" thick.
The rockers were fabricated from separate sheet and honeycomb over a mandrel to make the curve.
The most difficult of the construction is probably the glueing. Everything has to be prepped to a "T" to get a good bond onto aluminum. My guess is that it would take 1-2 man-months to do one chassis. Anybody volunteer to drill and rivet several thousand holes?
[ February 16, 2002: Message edited by: Bob Putnam -ERA- ]
Lots of glue (I think it was epoxy back then) and rivets.
It looks like in many places the glue was more important than the rivets. It makes sense, considering that the honeyco.mb skin was probably only about 0.025" thick.
The rockers were fabricated from separate sheet and honeycomb over a mandrel to make the curve.
The most difficult of the construction is probably the glueing. Everything has to be prepped to a "T" to get a good bond onto aluminum. My guess is that it would take 1-2 man-months to do one chassis. Anybody volunteer to drill and rivet several thousand holes?
[ February 16, 2002: Message edited by: Bob Putnam -ERA- ]
Jim Rosenthal
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I have gotten interested in this topic of composite chassis. Does anyone know of a book or monographs on car chassis construction from reinforced composites? There must be some kind of tech literature on this but I haven't found much. Maybe I'm not looking in the right place.
The Mark 4 chassis were also oven-baked, which makes me wonder if the adnesives used were indeed epoxies. They don't require baking to cure, and are not particularly heat-stable. But they will bond to aluminum; some of the proprietary systems even have bonding promoters available specifically for aluminum bonding.
It would be possible to build an entire chassis riveted and bonded with polyurethane adnesives, from aluminum. Would it be possible to build an entire chassis from fiberglass, or Kevlar, or CF, using epoxy or vinylester resin? There would have to be metal at points where you encountered certain types of stress; heat, for one, and very high local loads which might crack or break FRP components.
Correct me if I am wrong, but didn't the early Chaparrals use FRP chassis? I don't know how they mounted the engine, drive train, and suspension pieces. The composite technology available now is better than what they had; but they were competitive and won races as well.
Well, I will look around some more and if anyone comes up with anything, could they post it?
The Mark 4 chassis were also oven-baked, which makes me wonder if the adnesives used were indeed epoxies. They don't require baking to cure, and are not particularly heat-stable. But they will bond to aluminum; some of the proprietary systems even have bonding promoters available specifically for aluminum bonding.
It would be possible to build an entire chassis riveted and bonded with polyurethane adnesives, from aluminum. Would it be possible to build an entire chassis from fiberglass, or Kevlar, or CF, using epoxy or vinylester resin? There would have to be metal at points where you encountered certain types of stress; heat, for one, and very high local loads which might crack or break FRP components.
Correct me if I am wrong, but didn't the early Chaparrals use FRP chassis? I don't know how they mounted the engine, drive train, and suspension pieces. The composite technology available now is better than what they had; but they were competitive and won races as well.
Well, I will look around some more and if anyone comes up with anything, could they post it?
Most of the current racing chassis are carbon composites. It's usually necessary to have metal reinforcements around bolt holes, so sometimes an entire mounting bracket is bonded on for simplicity.
In spite of the availability of room-temp-cure epoxy, the best epoxies are (or at least were) heat cured. It makes construction easier by allowing the time of assembly to be much more flexible. The latest urethanes are good alternatives now.
The only books that I've seen on honeycomb construction have emphasized aircraft, but I wouldn't be surprise if there's something available for cars too. The problems are basically the same anyway. I think that
Fiberglast Developments may have some info too.
[ February 16, 2002: Message edited by: Bob Putnam -ERA- ]
In spite of the availability of room-temp-cure epoxy, the best epoxies are (or at least were) heat cured. It makes construction easier by allowing the time of assembly to be much more flexible. The latest urethanes are good alternatives now.
The only books that I've seen on honeycomb construction have emphasized aircraft, but I wouldn't be surprise if there's something available for cars too. The problems are basically the same anyway. I think that
Fiberglast Developments may have some info too.
[ February 16, 2002: Message edited by: Bob Putnam -ERA- ]
Hi Guys
This is the Lotus Elise chassis it wieghs in at 68Kg about the same as a ZF DS25/2 trans.
The aluminum chassis of the Elise is composed of 26 bonded parts. Some Ejot fasteners are only needed, in order to secure all sections, until the adhesive has cured completely. The chassis of the Elise weighs only 68kg and thus fewer as half, than a comparable welded chassis. Despite the low weight the chassis provides a very high torsional stiffness of 10133Nm/degree. Also extreme lightweight are the Elise's fiberglass body panels. The front clamshell weighs only 13,3kg and the rear clamshell only 15,3kg.
Chris
This is the Lotus Elise chassis it wieghs in at 68Kg about the same as a ZF DS25/2 trans.
The aluminum chassis of the Elise is composed of 26 bonded parts. Some Ejot fasteners are only needed, in order to secure all sections, until the adhesive has cured completely. The chassis of the Elise weighs only 68kg and thus fewer as half, than a comparable welded chassis. Despite the low weight the chassis provides a very high torsional stiffness of 10133Nm/degree. Also extreme lightweight are the Elise's fiberglass body panels. The front clamshell weighs only 13,3kg and the rear clamshell only 15,3kg.
Chris
G
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I have been to one site where they make a full tub chassis with carbon fiber. Even the bell housing was carbon fiber. The only metal was in the wheel/brake assemblies, engine and transaxle itself. Most parts are made with prepreg that is heat activated. The materials are stored in large walk-in coolers. This assures the optimal ratio of matrix to resin. Parts that are hand lain are then vacuum bagged which forces the excess resin out of the part. Metal pickup points are bonded in and the whole thing is put in an autoclave that is about the size of a 1 car garage. Autoclaves not only heat, but they also pressurize.
The Elise is not sold in the US, you can import them but they can't be registered for the street. There is a place that brings them in and converts them to US safety standard and puts in an Acura/Honda Integra type R motor, in all adding I think 55k to the price, its that or the total is then 55k
for the price tag I'd get a gt-40, but that's why I'm here in the first place.
for the price tag I'd get a gt-40, but that's why I'm here in the first place.
G
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I did work in the pits in the early 60s and saw Jim Halls car quite a few times, he may have had two cars 65 and 66. At frist people would refer to them as the plastic cars, I am sure it was a fiberglas tub with metal to reinforce it at attachment points. I do have pictures of these cars and will try and find them. A lot of these old pictures are in a house in Ireland that I have. Hall was real hot for a couple of years and the talk was what kind of automatic he was using. I believe it was a corvair two speed powerglide. The cars that I saw had the tall wing, however Bruce and Denny would always come in 2nd and third behind Hall. Bruce and Denny had two small green cars 4 and 5.That were no match for halls car. I heard bruce say at Laguna Seca that the next time he showed up he would have the new car to challenge Hall. After that bruce and denny had the bright orange cars and that was the end of Halls dominance. The chaparal was a beautiful car with clean lines and the mc larens were also beautiful. To my knowledge hall drove his own cars bach then and they were made in Midland texas, I think.
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