Replicar328
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| posted on 21/5/24 at 10:55 AM |
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Using a complete MX-5 front subframe
I've just bought an Alfa 33 tranaxle with a view to building a mid engined special.
Has anyone used a complete MX-5 front subframe in a Locost? If I understand correctly, the whole subframe assembly is attached to the MX-5 monocoque
with just six bolts - maybe more that I can't see, so a correctly designed spaceframe chassis could pick up on these locations and the whole
front end is done with the minimum of grief.
Apart from different spring rates, relatively little work. Okay, so it would be heavier than conventional Locost solutions but with the weight of the
engine at the back it'd be nicely balanced.
Just wondering, has anyone tried this? Drawings/pictures would be nice!
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jacko
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| posted on 21/5/24 at 11:25 AM |
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So you are saying you want to use a front subframe at the rear ami correct? And lock the steering
I have just looked at google images and there is quite a bit of info you may get off there
G
555
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Slimy38
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| posted on 21/5/24 at 11:31 AM |
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Well, if MEV use it for basically all their cars (including the Exocet which is 'sort of' Lotus 7 ish?), then I don't see why you
couldn't do the same. One of their selling points is that less than a dozen bolts will allow the body to lift up and over, then the new body is
dropped in place.
However, don't expect a 'minimum of grief'. As with all donors, you're going to need to recondition a lot of things. Even basic
things like the eccentric bolts for suspension adjustment are roughly £10 each, and I really didn't enjoy taking mine apart. Bushes, ball joints,
TRE's etc, they all add up.
I'm not sure how much time and money you'd save using the subframe. Of course, you could ignore all the reconditioning stages if you really
wanted to save money!
Edit: Ignore some of that, I've just realised what you're trying to do... that's possibly a bit more design work than just reusing the
subframe. Not impossible though.
[Edited on 21/5/24 by Slimy38]
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Ugg10
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| posted on 21/5/24 at 11:47 AM |
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Also have a look at the MEV Replicar, not sure who currently owns the manufacture rights to this, but this uses the whole Mc5 chassis including front
and rear subframes and also the crental backbone.
The other one to look if you are going mid engine is the Jeremy Philips car that uses the MGF as a donor bolting the front and rear subframes onto the
chassis, iirc it was called the Vectis (maybe), others will correct if not.
Finally there are a number of kits that use the Subaru Impreza front end in the rear of cars, the 818 in the US is the first to come to mind.
---------------------------------------------------------------
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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Replicar328
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| posted on 21/5/24 at 12:37 PM |
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Wow, super responses, and so quickly! Great to hear that this has been done before - I may be crazy, but I'm not the only one....
Just to clarify, I'm looking at using the complete front assembly at the front. The whole rear assembly at the rear may be possible too, but I
won't be using the PPF and the rear subframe may not clear the intended boxer engine and transaxle bell housing. I'll probably look at
buying an MX-5 in reasonably good condition with the hope of avoiding significant refurbishment cost.
Designing a chassis is not trivial but I've got an unused very well made Locost chassis which I can probably chop with the help of a professional
welder who works three doors down from me.
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jacko
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| posted on 21/5/24 at 04:58 PM |
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I have to ask if you have a good locost chassis why are you not using the front suspension of that?
G
555
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JC
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| posted on 23/5/24 at 04:16 AM |
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I can see the attraction of using the entire front subframe. I considered doing something similar for my mid-engined car, but came to the conclusion
that by the time I had done all the work to incorporate it into a chassis, I may as well just design something bespoke - the compromises weee too
great!
If you have an existing Locost chassis, there are already solutions out there that use Locost-Esque suspension with MX5 uprights - that may be easier
and ultimately more effective.
You could trawl through my old blog for inspiration…..and how not to do it ideas www.mistrale.blogspot.com
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Robski
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| posted on 23/5/24 at 06:33 AM |
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I looked at the MEV Exocet with its use of both MX-5 subframes. Still not ruled out building my own chassis along those lines.
BUT.
The front subframe of the MX5 isn't just the place to hang the suspension and steering: it also cradles the engine. It's a great example of
integrated design by Mazda and not very heavy given its intended purpose.
But if you don't use it for what is arguably its main job - holding the engine in place - surely it becomes a very heavy and probably overly
large steering and suspension unit!
BTW, why not sell the Locost chassis and start again. Butchered metalwork either looks butchered, or requires so much finessing it may have been
easier to just start again.
[Edited on 23/5/24 by Robski]
Rob.
Hoping to build a 4 wheeled bike!
Fast, nimble and delinquent!
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Replicar328
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| posted on 25/5/24 at 09:19 AM |
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Thanks for all the useful responses from those with far more experience than I.
I’m now leaning towards using both the front subframe with all the items that come with it and the rear subframe with the Alfa transaxle instead of
the diff with whatever mods are necessary for the driveshafts and a custom chassis.
Anyone looking for a professionally made Locost chassis?
I could really do with a dimensioned drawing of the rear subframe to check if the Alfa transaxle will clear it? But I admit it may be just as easy to
incorporate the inner pick up points of the wishbones directly on a custom chassis
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Fred W B
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| posted on 25/5/24 at 05:39 PM |
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I give this advice to everyone who asks about building a mid engined car from scratch.
Decide what the car is going to look like, i.e what body shell, if not original. This also determines wheel base dimension and the width over wheels.
i.e determine the wheel positions.
If original body, decide on at least the front and rear track, wheel base can be adjusted.
Decide on what tyres you will use, exact width and profile, and procure if you are serious.
Decide on what hubs/uprights/steering rack you will use and procure/make if you are serious
Decide on what rims/offset you will use and procure if you are serious
Decide on what engine and transmission you will use and procure if you are serious.
Position all above parts on garage floor or build table and sort ergonomics – where do you fit?
If you are going to draw up in cad, finalize the position of all above parts in your model only now.
All the above could be an iterative process, but please complete it BEFORE you start the chassis.
Design suspension – if you are not going to do the research to enable you to do this yourself the only options are:
Get someone else to do it for you
Copy an existing car, strictly only valid if using that cars uprights/hubs/wheels/tyres.
Guess
Once you know where the inner suspension points are, you can design the chassis, to accommodate all above. CAD / balsa model / cut and tack on build
table are all valid methods, but best results would be obtained by combining them. Please do not start with a Locost chassis and try to modify it to
accommodate a Rear engine drive train.
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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Replicar328
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| posted on 26/5/24 at 10:21 AM |
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Thanks for the advice Fred W B. I’ll make use of it to edit my ever-growing checklist!
You’ve nicely described how difficult it is to start with a clean sheet of paper – it’s necessary to introduce constraints to get started, which may
change along the way.
This project was inspired by the original Alfa 33 Stradale, not the official Alfa 2023 replica which simply doesn’t have the beauty of the original.
I’ll probably build it with a simpler body to get through the UK legal requirements but I’ll try to build a chassis which could later accommodate a
sleek bodyshell. I’m planning a road legal car with maybe 20% of the power of the T70 so some of the considerations necessary for a race car do not
apply.
Using the MX5 subframes with suspension layout makes life easier than it would be if starting from scratch. Using road tyres makes the suspension
dimensions less critical. Same wheelbase (maintaining Ackerman), hubs/uprights/steering rack and same track back and front, same wheels and tyres
My centre of gravity will be low, the overall weight will be less and the CG will probably move backwards a bit. To keep the front end low and to
soften the springs I may have to bring the front suspension inboard using coilovers which will make front end adjustments simpler.
The engine will be an Alfa boxer – from an Alfasud, 145 or 33. The inlet manifold is a bit of a monster so I may look at feeding either side of the
engine through separate air filters and install an aftermarket EFI. Finding room for the exhaust pipes may be an issue! Probably two small radiators
in series, one on each side, with air intake mimicing the Stradale.
I’ve already taken onboard the advice not to use the Locost chassis. With the MX5 components mounted in position on the garage floor I will build a
spaceframe chassis in wood. I haven’t yet completely dismissed the idea of a marine ply chassis – I owned a Clan Crusader years ago and it was
blisteringly quick around corners in spite of the fairly primitive Hillman Imp suspension.
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russbost
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| posted on 28/5/24 at 05:27 PM |
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No one has pointed out that using the MX subframe whether at the front or rear means using the McPherson strut suspension that comes with it, unless
you're planning on somehow hanging a top wishbone off the subframe. I would have thought that would be very restrictive in terms of the overall
packaging, both in height & restricted width between the turrets.
To the best of my knowledge no one produces anything like the old Mini, Cortina or Viva subframes that had all the suspension (double wishbones)
already attached, that simplified so many things with those builds ....
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Replicar328
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| posted on 28/5/24 at 08:27 PM |
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I think you’ll find, the MX5 is double wishbone back and front?
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russbost
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| posted on 28/5/24 at 09:00 PM |
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quote:
Originally posted by Replicar328
I think you’ll find, the MX5 is double wishbone back and front?
Apologies, I'm not very familiar with the Mx5, I'd looked at Exocet front suspension in passing & had assumed it was struts due to the
large, strut like front shocks.
However, still stands that you'd either need to replace those with something much smaller & create a suitable mounting , or you'd have
the same sort of height/width restrictions ax you would with struts, they are a similar size & position
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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Replicar328
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| posted on 28/5/24 at 09:21 PM |
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Indeed, it’s why I mentioned the possibility of bringing the front springs inboard. Using a push rods, lever arms and coil overs. Lots of room with
engine at the back, and easily adjustable!
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russbost
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| posted on 29/5/24 at 07:11 AM |
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quote:
Originally posted by Replicar328
Indeed, it’s why I mentioned the possibility of bringing the front springs inboard. Using a push rods, lever arms and coil overs. Lots of room with
engine at the back, and easily adjustable!
Yes, can see the logic behind that, to a certain extent, it might depend on how visible the suspension is going to be, the MX5 stuff isn't
particularly pretty!
I no longer run Furore Products or Furore Cars Ltd, but would still highly recommend them for Acewell dashes, projector headlights, dominator
headlights, indicators, mirrors etc, best prices in the UK! Take a look at http://www.furoreproducts.co.uk/ or find more parts on Ebay, user names
furoreltd & furoreproducts, discounts available for LCB users.
Don't forget Stainless Steel Braided brake hoses, made to your exact requirements in any of around 16 colours.
http://shop.ebay.co.uk/furoreproducts/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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