ausmini :: View topic - Dutchy’s MiniRex

I've previously read about roll frequency, that is how quickly a suspension rolls, the explanation for a inclined roll axis was that the front is the first to experience the lateral acceleration and roll, the rear experiences it only after and because of the front.
If the roll moment was the same the front would roll then the back leading to a vague, delayed and weird feeling (technical term).
I believe I've felt this in my mini (which has a declining roll axis) on a short sharp corner it felt fine on a longer faster corner it felt like the rear wouldn't decide what it wanted to do, grip or step out. I partially solved it with progressive bump stops on the rear, I believe it was relatively quickly settling on the bump stop meaning the rear roll frequency better matched the front.
I've managed to try and sort the minis skewed roll axis by raising the rear roll axis, it's passed engineering but isn't registered yet so I've not much idea of it has improved things markedly.
With most of your weight centered it might be a safe bet for a relatively flat roll axis, I'm not sure it hasn't something to do with where most of the weight is as well as weight will generate roll.

Author:	Dutchy1978 [ Sat Aug 08, 2020 12:12 am ]
Post subject:	Re: Dutchy’s MiniRex
I’m glad I have a hoist. Makes life so much easier Tonight was a win in my opinion. While I didn’t do much I managed to tack the subframe I made to the engine subframe to make it all one piece. It took a while to get it mm perfect but in the end was worth it. Finished with the perfect track width I wanted, perfectly centre of the engine and the body as well. The wheels sit exactly where I wanted them too in regards to the wheel arch location. I have a bit of wiggle room in case I have to move the engine and drive chain forward a cm or two which is handy. I just need to sort out the height and continue on with making a mounting point for the upper control arms.

Author:	murty [ Sat Aug 08, 2020 2:54 am ]
Post subject:	Re: Dutchy’s MiniRex
Very cool. Reminds me of a mad type of Renault R5 Turbo.

Author:	fuzzy-hair-man [ Sun Aug 09, 2020 4:10 pm ]
Post subject:	Re: Dutchy’s MiniRex
Are you going to bolt the rear subframe and engine frame to the backs of the mini sills? Or is there some other plan? Are water and intercooler? pipes going up the tunnel? Wondering about a tube inserted up the sills like project binky did or a sort of frame up the tunnel like the mx5 uses, except there's not much room in a mini's tunnel. Is the plan to pick up the rearmost 2 mounts for the minis rear subframe? Sorry for all the questions, there was a guy on 16v mini forum was planning a rear engined subie powered mini but out never got there, the low COG, and nice balance of a boxer appeals to me.

Author:	Dutchy1978 [ Sun Aug 09, 2020 5:53 pm ]
Post subject:	Dutchy’s MiniRex
Lots of good questions. All of what I had to think of before going ahead. The idea is as follows: - Cooling to go up the tunnel to the radiator. Electric water pump is still being considered. - 75x50 RHS will go down the inside of the sills forming part of the chassis for strength. (Inside the car) - This will continue right to the back of the car (with some angles) where the engine and gearbox subframe will bolt too. - I’ve left the original rear subframe mounts in case they can be used. It will depend on the height of the chassis rail.

Author:	Harley [ Sun Aug 09, 2020 6:57 pm ]
Post subject:	Re: Dutchy’s MiniRex
On the cooling side of things I’d be inclined to looking into the electric water pump, possibly in addition to the factory pump on the engine if it can be made to work that way. The cooling system will be dealing with more than the original pump was designed to cope with, so an upgrade would certainly be a good idea. If you do go with the electric one, maybe put an extra switch somewhere so you can run the pump without the engine running as a means to help drain and fill the cooling system.

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Author:	fuzzy-hair-man [ Sun Aug 09, 2020 7:54 pm ]
Post subject:	Re: Dutchy’s MiniRex
Harley wrote: On the cooling side of things I’d be inclined to looking into the electric water pump, possibly in addition to the factory pump on the engine if it can be made to work that way. Another forum and a engine conversion used a electric water pump and everyone seemed set against it, I don't really understand why as electric pumps have more than proven themselves in auto applications, the ability to control pump speed gives better control of engine temps and I think means you can get rid of the thermostat.

Author:	Harley [ Sun Aug 09, 2020 8:08 pm ]
Post subject:	Re: Dutchy’s MiniRex
I’d have no problem using an electric water pump, many european cars ditched mechanical ones a decade ago. Provided they’re a good quality unit they can run reliably for a very long time.

Author:	Dutchy1978 [ Sun Aug 09, 2020 11:12 pm ]
Post subject:	Re: Dutchy’s MiniRex
Agree with the electric pump however just making work with the boxer will be a challenge as I’m trying to do this build without pulling the engine apart. It only has 100,300kms so if I can avoid it I will. Additional electric water pump might be the go.

Author:	Dutchy1978 [ Sun Aug 09, 2020 11:15 pm ]
Post subject:	Re: Dutchy’s MiniRex
After cutting the original WRX subframe up it needed some strengthening. Also welded up the rest of it after checking everything lined up.

Author:	fuzzy-hair-man [ Thu Aug 20, 2020 10:20 am ]
Post subject:	Re: Dutchy’s MiniRex
fuzzy-hair-man wrote: I've previously read about roll frequency, that is how quickly a suspension rolls, the explanation for a inclined roll axis was that the front is the first to experience the lateral acceleration and roll, the rear experiences it only after and because of the front. If the roll moment was the same the front would roll then the back leading to a vague, delayed and weird feeling (technical term). I believe I've felt this in my mini (which has a declining roll axis) on a short sharp corner it felt fine on a longer faster corner it felt like the rear wouldn't decide what it wanted to do, grip or step out. I partially solved it with progressive bump stops on the rear, I believe it was relatively quickly settling on the bump stop meaning the rear roll frequency better matched the front. I've managed to try and sort the minis skewed roll axis by raising the rear roll axis, it's passed engineering but isn't registered yet so I've not much idea of it has improved things markedly. With most of your weight centered it might be a safe bet for a relatively flat roll axis, I'm not sure it hasn't something to do with where most of the weight is as well as weight will generate roll. A better explanation of roll frequency than I could manage in the second half of this video. https://youtu.be/JxOBw78DXBQ

Author:	fuzzy-hair-man [ Thu Aug 20, 2020 3:50 pm ]
Post subject:	Re: Dutchy’s MiniRex
Sorry, I'll stop being a PITA but I'm bored and youtubing... Anyway I came across another video talking about Gordon Murray's T50 car but he discusses the ideal roll axis and centre of gravity for a mid engined car and it was too relevant not to share. Skip to 45.00 of the rest isn't of interest. https://youtu.be/NT8PMXCMrsM

Author:	Dutchy1978 [ Fri Sep 11, 2020 8:10 am ]
Post subject:	Re: Dutchy’s MiniRex
There’s been a fair bit done since the last post including building the chassis rail to tie the front and rear together. The engine/rear suspension subframe is pretty much done now. It will need some tweaks and small brackets added for cables, brake lines etc. wheel arches still need to be made but I’ll strip the paint to see if any of the body needs repairing first. Im pretty happy with its ride height and the progress so far.

Author:	Dutchy1978 [ Fri Sep 11, 2020 8:13 am ]
Post subject:	Re: Dutchy’s MiniRex

Author:	Dutchy1978 [ Fri Sep 11, 2020 8:22 am ]
Post subject:	Dutchy’s MiniRex
Now working on the front suspension. I had to cut the guards to start with and of course found some decent rest between the panels. So I know there’s gonna be a bit of bodywork to be done down the track. I’m hoping to use the front suspension from the MX5 so it matches the rear however the only way I can make it work at this point is by having the LHF lower control arm reversed and used as the RHF lower control arm. Not sure whether the engineer is going to be happy with that or not but realistically it’s going to do exactly the same thing and in fact is pretty much like the original mini suspension anyway with the tiebars towards the front rather than the rear. Let me know your thoughts or ideas on if it will work.

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Author:	fuzzy-hair-man [ Fri Sep 11, 2020 10:49 am ]
Post subject:	Re: Dutchy’s MiniRex
Dutchy1978 wrote: Let me know your thoughts or ideas on if it will work. I've been waiting for an update... I think it'll work it doesn't seem to matter much if they are supported from the front or back judging from OEM designs. The relative height of the front and back dictate anti dive and anti squat characteristics which will be important. Are the angles on the lower ball joints ok once turned around? The shorter track and wheel base will effect the mx5 geometry anyway imo but longer arms tend to give better control of camber etc anyway, so probably work in your favour. I know the minis suspension is old but what was the reason to abandon the mini suspension perhaps with coil overs? Wheels & hubs?