ludsonline
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| posted on 21/9/16 at 05:03 PM |
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Chassis build with standard MX5 subframes
Hi,
Has anyone built a chassis using standard MX5 front & rear subframes?
Cheers
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Slimy38
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| posted on 21/9/16 at 05:46 PM |
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I believe there have been some that have used the rear subframe, but apart from MEV cars I don't think any have used the front. They're
not the lightest things in the world, and would also require large chassis mods to mount them.
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nick205
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| posted on 22/9/16 at 10:24 AM |
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The sub frames look fairly large to me and I suspect would take quite some effort and skill to "fabricate" into a 7 type chassis.
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ludsonline
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| posted on 29/9/16 at 11:27 AM |
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Thanks for the replies, It's not going to be locost shaped, just wondering about the chassis side of things.
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Ugg10
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| posted on 29/9/16 at 12:37 PM |
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Look at pictures of the MEV Replicar, it uses both front and rear mounted onto a spaceframe (with Aston DBR1esque body) and the MEV Exocet which is
similar but in an EXO car style frame -
http://www.mevltd.co.uk/kit-cars
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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ludsonline
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| posted on 29/9/16 at 01:20 PM |
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Cheers for those, do you know what size box the Replicar chassis is?
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Ugg10
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| posted on 29/9/16 at 01:53 PM |
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No idea but looking at the pictures it is a mix of square and round tube, square tube looks to be about 1" square and the round tube
1.5-2" diameter. But that is just an eye ball guess. Lots of pics form various build sites if you google the images.
---------------------------------------------------------------
1968 Ford Anglia 105e, 1.7 Zetec SE, Mk2 Escort Workd Cup front end, 5 link rear
Build Blog - http://Anglia1968.weebly.com
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Beardy
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| posted on 10/10/16 at 09:28 PM |
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I had the same questions (posted in Chassis).
There are tube subframes available for the Miata so it doesn't need to be a big weight penalty.
But perhaps tangential to this discussion I was thinking more of a ground up chassis homebuild rather than a kit. I figured that using the subframes
saves a lot of brain ache and skill getting the suspension and steering geometry bang on from a fabrication standpoint. Using an NC Miata immediately
gives you the Duratec drivetrain.
I'm surprised its not a more popular given the advantages.
Beardy
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ludsonline
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| posted on 11/10/16 at 01:33 PM |
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I'm with you on that one Beardy, don't understand why it's not more popular.
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rossnzwpi
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| posted on 20/9/17 at 06:33 PM |
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Quite a few people have used the MX5 (even the NC) as the basis of a scratch-built car. It is one solution I have thought of and for similar reasons
to you. I don't have the skills to design a suspension from scratch. A couple of points:
1.) you can do away with the subframes if you are designing the chassis from scratch. Just take measurements from the subframes and integrate those
points into your chassis. Subframes are often used as a device to isolate shock from the body.
2.) I'd really like to know what effect it would have on the geometry to narrow the track or change the wheelbase. Say I took a MX5 front
suspension but narrowed it by 100mm by just moving the wishbones inward and replacing the steering rack with a narrower one. Does this wreck the
suspension's function? I'd do the same at the rear using narrower drive axles.
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Camber Dave
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| posted on 21/9/17 at 01:23 PM |
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Quote from rossnzwpi
"Quite a few people have used the MX5 (even the NC) as the basis of a scratch-built car. It is one solution I have thought of and for similar
reasons to you. I don't have the skills to design a suspension from scratch. A couple of points:
1.) you can do away with the subframes if you are designing the chassis from scratch. Just take measurements from the subframes and integrate those
points into your chassis. Subframes are often used as a device to isolate shock from the body.
2.) I'd really like to know what effect it would have on the geometry to narrow the track or change the wheelbase. Say I took a MX5 front
suspension but narrowed it by 100mm by just moving the wishbones inward and replacing the steering rack with a narrower one. Does this wreck the
suspension's function? I'd do the same at the rear using narrower drive axles."
Reply to Q2)
For a Miata, Eunos or MX5 mk1 donor subframes
Rear end - No issue - Roll centre remains the same. The control of the roll centre with chassis roll is actually improved.
Use a ride height that sets the lower inner bush centre at the same height as the lower, outer wishbone pivot.
Front
Overall not as good, quite bad really. (As Is the standard car - excessive roll-centre propagation )
However by lowering the upper wishbone pivots by 30mm the roll centre remains close to its static location.
Use ride height with lower wishbone inner 15 to 20mm below centre of lower ball joint.
These ride heights give the best roll axis with the donor components.
Wheelbase - use 2.3 Meters if possible - It works on hundreds of different cars from Lotus Elise, TVR, Westfield ect ect.
Background theory
Excessive roll centre movement as the car rolls causes the front to feel imprecise and hard to position accurately ie understeer.
It is probably designed in to give the driver clear warning of limit of adhesion.
The standard car is quite soft and rolls a lot
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