Steel welded frame vs Monocoque

I am in the early stages of selecting a kit. For the guys that have welded steel frames are you satisfied with your choice? For street driven car, does monocoque offer any advantages?
 

Davidmgbv8

Supporter
Curious,how much is a monocoque? With suspension? Thought the price was significantly more than a welded tube chassis?
 
Cheaper monocoque? Not around here. The CNC parts alone (>100 separate parts) are worth what a tube chassis costs to put together, and it takes about twice as long to assemble (not including what a tube chassis requires for adding the sheet metal.)
 

Kevin L

Supporter
Frank, I realize this question may be hard to answer but.... from your experience driving an original vs. a replica monocoque; are there driving differences? I ask because I really enjoyed driving my replica but there was always a question about how much the replica drove like one built in the 60s.

Of similar interest is P/1085 which sat as a kit of parts for a long time before being built up... does it drive similarly to a replica?

Kevin
 

Randy V

Moderator-Admin
Staff member
Admin
Lifetime Supporter
Having driven original mono on track, and most of the replica market cars, including the monocoques, my choice is the original, by a long way
That’s pretty interesting given the poor quality materials (un-galvanized, thin mild steel) that was used in the original chassis. Not to mention the much higher quality tires, springs, shocks and brakes being used in most replicas…. I’m not saying you are mistaken - just extremely curious how this can be… Possibly the Steel spider vs. Fiberglass as used by nearly all replica houses?
Or is it analogous to perhaps an Audiophile that prefers the more mellow and dampened analog sounds from a tube type amplifier vs. modern digital technology?
 
^ exactly. An original mono is likely fitted with period looking tires, perhaps bias ply. That one change in spec from a modern radial changes quite a lot. Second, if the repro is a mono, does it use original pick-up points? If so, camber/castor rates may not be great for a modern low profile tire.
 
I would guess that it is the total package of a original style mono car;
Your shifter is basically steel to steel all the way to the transmission, no cables.
Suspension is either rosejoint or bearings, no bushings that provide any flex or dampening.

Very few offers a monocoque as a loose item and trying to make alot of parts from different suppliers fit together sounds like a bad idea.
 
On the topic of the original monocoque chassis, does anyone know what the thickness/guage of the sheet steel was and what the specific grade of steel used? In doing comparison to some of the modern replicas currently available, I’m curious how the basic material strength compares (I realize there is a substantial amount more that goes into the final strength of the chassis, well beyond what an enthusiast could determine, but basic material does play a role).
 

Davidmgbv8

Supporter
So funny enough I was wondering what the torsional values of a monocoque vs an SGT chassis. As I was wondering would FAV been better offering a semi stressed tubular chassis that was less costly to build?
 
So funny enough I was wondering what the torsional values of a monocoque vs an SGT chassis. As I was wondering would FAV been better offering a semi stressed tubular chassis that was less costly to build?
I remember there is a very old thread some where on this website. IIRC the Monocoque is quite a bit stronger, *** BUT the whole discussion turned into a shit fight due the the method used at front and rear of the chassis to attach it to a plate that allowed it to be attached to the jig/fixture being used to apply the torsion force. Onece all our manufacturers started touting their designs as being better than others the whole discussion fell to bits.
 
On the topic of the original monocoque chassis, does anyone know what the thickness/guage of the sheet steel was and what the specific grade of steel used? In doing comparison to some of the modern replicas currently available, I’m curious how the basic material strength compares (I realize there is a substantial amount more that goes into the final strength of the chassis, well beyond what an enthusiast could determine, but basic material does play a role).
Mainly 0,7 0,9 and 1,2mm. The specified material is en2b which is mild steel with very vague mechanical requirements in the datasheet.
 
0.036" EN2B for the most part.

There are some parts that are thicker, and some parts that are thinner but most of it appears to be 0.036"
 

Eddy McClements

Supporter
So funny enough I was wondering what the torsional values of a monocoque vs an SGT chassis. As I was wondering would FAV been better offering a semi stressed tubular chassis that was less costly to build?
Didn't Eric Broadley prefer a rivetted aluminium mono, but Ford wanted a steel chassis to provide a (spurious) marketing tie-in with the upcoming Mustang? And so the GT40 was saddled with a slight weight penalty from the outset and broke transmissions and cooked brakes from the get-go? There's a thread somewhere....

Edited to add...found it:-

 
Yes Eric liked the idea of an aluminium chassis.
However as I understand it Ford wanted a steel chassis because it was judged a more simple, easier to work with material. It would also be better for the road car derivative, plus aluminium was not a familiar material to Ford Motor Company for chassis or body work at that time. I see steel being the 'easy' answer to FoMoCo.

I've never heard of an attempt to connect the steel chassis GT40 to the Mustang for marketing, just because both are steel. I don't see that at all. Besides which the Mustang had been on sale nearly a year before the GT40P/xxxx production series began to be built & despatched from FAV at Slough. The GT40's successes were yet to come.

The Italian gearbox couldn't last with the power & torque of the V8, I don't think a lighter chassis would have been enough to save it, especially over 24 hours. The brakes really became an issue with the MK II. The increase in performance from the big 427 & the frequent braking from over 200 mph led to over worked brakes.
 
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