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K3 changes to the car suspension and drive 
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Part built GTM

Joined: Tue Feb 23, 2016 11:14 pm
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Post K3 changes to the car suspension and drive
Looking at a complete rebuild from a preregistered car, that has been taken to bits and boxed up. I am looking at a long term build, possibly 2 years.
Thinking of the following changes and would be interested in forum views and if any of them have been done before.

1. Change the front sub-fame for something lighter and with more adjust ability built in. Thinking along the lines of a grp/metal composite box. Keeping the hubs and wishbones from the original but getting rid of the hydrogass. Possible weight saving 30kg.

2. Change the rear to something similar to the front idea. Same sort of weight saving.

Now the off the wall idea.

3. Change from petrol to electric using the drive system from something mainstream like Nissan leaf. Here are my thoughts on this one so far. drive system is a nice compact package. Battery pack could be used to get better weight distribution. Reasonable horse power, considering how light the car would end up. Car unlikely to be used to exceed the battery range, used as a fun town runaround or short days out. More electric charge points are now available as well for longer drives. Being electric may be zero tax. Finally its different and generally a lot cleaner.
I have full workshop facilities for all of the above so manufacturing is not a problem, I have access to a 1st class honours motor sport engineer who has looked at the ideas and cant see any major problems. He thinks the biggest issue will be getting the weight distribution and spring rates right.

I am not looking at resale value as the whole project is more about doing things myself and having a bit of fun. If it works it may be worth a fortune who knows, it certainly wont be worth less than the boxes of bits.
So what do the forum members think.
Good or bad I dont mind I just want to find out what others think.


Sun Jan 08, 2017 12:17 am
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Post Re: K3 changes to the car suspension and drive
You could easily use MGTF subframes. You then can use coilovers


Sun Jan 08, 2017 5:53 pm
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Post Re: K3 changes to the car suspension and drive
I have MG TF and metro sub frames with complete suspension and running gear. The TF suspension was my first choice to get rid of the hydro gas. Then once I started to look closer I discovered the amount of weight in the sub frame. It was at this point I started to look at how to get rid of some of this weight. What we ended up with was a list of parts we didn`t want to change and bits which we thought could be improved.
We are looking at a GRP or GRP composite box like sub frame with the suspension bolted onto it. Similar to the front of the Libra. This would then be bolted to the original mounting points of the metal sub frame.
We gain a big weight reduction but keep the suspension components standard, which helps with future repairs and maintenance. We are looking at different hubs to get a better PCD for the wheels.
This may help with future wheel and tyre choices.
So far we have 3d modelled the new proposals and they look good, the stress analysis of the model also looks well up to the loads we thing will be placed on it.
Once I work out how to get a picture on the forum I will post what we have so far.


Sun Jan 08, 2017 6:18 pm
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Post Re: K3 changes to the car suspension and drive
The 2 images are the simplified front sub frame proposal. The 1st one has the top removed to show the space which could be used for fuel or battery pack. The space could also be used as storage.
The second image shows the box section sealed off and working as a structural member.
The wood texture is used to get a better appearance of the set up, it would be made in a number of different materials to make up a composite panel which could be as light as 10kg with a target of 15kg.
Attachment:
Assembly frame 1.jpg
Assembly frame 1.jpg [ 313.04 KiB | Viewed 9561 times ]


Attachments:
Assembly frame 2.jpg
Assembly frame 2.jpg [ 307.01 KiB | Viewed 9561 times ]
Sun Jan 08, 2017 6:46 pm
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Post Re: K3 changes to the car suspension and drive
Will a mgtf sub frame drop straight in each end for using coilovers and every thing else bolt in place easily or is there a lot of welding etc to do?


Sun Jan 08, 2017 10:55 pm
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Post Re: K3 changes to the car suspension and drive
From the measurements I have taken and what is on the forum and internet it looks to me that the sub frames are a straight swap. From the forum it would appear that changes may be needed around the engine and gear box mounts of the sub frame.


Mon Jan 09, 2017 12:00 am
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Post Re: K3 changes to the car suspension and drive
I guess it that in the MGTF the front frame obviously didn't have an engine in it and the rear frame has a different suspension arrangement fitted. Are the engine and box mounts bolt on or welded on. Sorry not go mine stripped that far at the moment.


Mon Jan 09, 2017 8:19 am
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GTM: K3
Post Re: K3 changes to the car suspension and drive
Attachment:
MGF rear subframe.JPG
MGF rear subframe.JPG [ 239.32 KiB | Viewed 9511 times ]
Attachment:
K3 front subframe.JPG
K3 front subframe.JPG [ 275.7 KiB | Viewed 9511 times ]
Attachment:
K3 Front Subframe 2.JPG
K3 Front Subframe 2.JPG [ 248.01 KiB | Viewed 9511 times ]
Hi Here is a picture of my replacement front subframe, made so that I can dump the hydragas for coilovers. It was made from thickish tube and ended up around 5kg lighter than the metro one. I also made my own wishbones and retained the metro hubs.
The second picture shows it fitted to the tub, (original mounting points).
The last picture is of the MGF rear subframe, it does need a couple of brackets grinding off and engine and gearbox mountings modifying. As shown the rear suspension is different to the metro in that it has a trailing arm, a control arm and the original top arm. I understand that the TF subframe is different to this with a bigger trailing arm etc. I converted this one to take coilovers as well with retro fitting brackets. Also with the TF subframe you will need to devise a bracket arrangement to attach the torque tube to that comes from the tub.
Hope this helps,
Peter.


Mon Jan 09, 2017 1:58 pm
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Post Re: K3 changes to the car suspension and drive
Nice but a whole level of skill don't have!!! :cry:

Have you settled on a spring/ damper set up that works with your brackets? and do they work on the front as well as the back. Is your car for road or track?
Malcolm
ps sorry to hijack the thread with other questions.


Mon Jan 09, 2017 2:36 pm
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GTM: K3
Post Re: K3 changes to the car suspension and drive
Hi Malcolm,
Check out Olivers post "coilover dampers" to see more of what we are trying to achieve. I used GAZ 13" adjustable dampers and coil springs, 200lb on the front and 300lb on the rear. Having corner weighted the car they seem ok but I need an mot on the car next to try them out.
The brackets fit on the front or rear of either metro or MGF subframes.
Peter.


Mon Jan 09, 2017 4:50 pm
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Post Re: K3 changes to the car suspension and drive
Great to see some discussion taking place.
It was the PEEPS front sub-frame that started me on the path I have been heading.
Closely followed with Olivers coil overs. I then looked at both ideas and had the following thoughts.

Can I get things even lighter?
Can I get a sub-frame needing minimal specialist skills?
I had looked at the idea of laser and water jet cutting of the parts and have still not ruled this out.

It was at this stage I then started to think about a different mechanical package for the drive train.

A troll of YouTube produced some interesting information.
Worth a look are the 3 videos by Rob Smith, starting with

2012 Nissan Leaf Teardown / Component Locations

This started the idea of the electric conversion which I think could be packaged nicely on the car to get good weight distribution.
I would be interested in peoples thoughts on the drive train idea.


Mon Jan 09, 2017 7:43 pm
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Post Re: K3 changes to the car suspension and drive
I take it from the numbers of readers and the lack of comments there is no interest in the electric idea. Or you think I am mad and are to polite to say.
To help things along and possibly get some help. Good or bad. Here are my calculations and conclusions. I have based my work on the car being totally empty no seats or anything other than wind and weather proof and running. The reason for this is what we choose to put in and on our cars makes each one totally different. The numbers shared are therefor the absolute best possible and would not be achievable in the real world. They are for discussion.
Lets look at a standard cars no modifications, both systems can easily be improved.

1.8Lt Rover engine produces
134 bhp 122 lbs/ft ( Max ) giving a power to weight ratio of about 223bhp/t

Nissan 30kn leaf unit
120bhp 207lbs/f ( Constant ) giving a power to weight ratio of about 200bhp/t

The 23bhp/t short between the petrol and the electric will not be noticeable in normal driving, what will be noticeable is the constant push from the flat delivery of torque from the electric. I think it will feel a lot more powerful engine than its numbers suggest.
The 23bhp/t may also be bridged due to the lack of things like petrol tanks fluids for heating and cooling, radiators and pumps for controlling things and many other items not yet investigated and accounted for. Even removing the need for a gear linkage will be saving weight in the electric version.
All of this weight saving will also allow for lighter sub frames and suspension systems, this again would improve the bhp/t figure. It may with time be easy to work out a way of surpassing the petrol engine bhp/t and keeping the advantage of the torque.
Being into kit cars suggests we are more open to new ideas than most. What I need is some feedback, I cant be the only one looking at changes to keep our little beauties on the road. I love the look and proportions as much as anything. I love the fact I have not seen one on the road in Scotland, I dont think I have ever passed one on the road anywhere. Exclusivity rules.
My choice of power is the bottom of the electric car world, what about moving to Tesla running gear?
The power sky rockets but the weight hardly changes. Its clean and quiet, mind you I think I will miss the noise of the engine. I should confess I am no sandal wearing, tree huger who hopes to save the earth. I drive a huge German v6 turbo diesel 240BHP 450 lbs/ft daily along with a range of 4 other petrol cars I use regularly for other purposes. I rack up about 30,000 miles in a year so they are not all toys.


Fri Jan 13, 2017 11:03 pm
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Post Re: K3 changes to the car suspension and drive
Really impressive work on the sub frames

Electric power could be pretty cool but I think if I were you I'd be putting a K series in it. Maybe a revvy tuned 1.6 rather than a 1.8...

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Sat Jan 14, 2017 9:04 am
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Post Re: K3 changes to the car suspension and drive
I think fitting electric running gear into a light weight kitcar is a great idea.
But where do you find a donor vehicle from? There can't be many Nissan Leaf's in scrapyards yet.
Also don't the batteries weigh a considerable amount. Would getting the weight balance right be a problem?
I'd be very interested to see this done if you do go ahead with it.

Also wasn't there something a couple of years ago about Westfield fitting a Libra out with electric running gear??

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Sat Jan 14, 2017 9:39 am
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Post Re: K3 changes to the car suspension and drive
Like the electric motor idea, it really would be novel to produce an electric powered GTM; as Sven says, I think it was Westfields intention to produce an electric GTM at some point.

I think the prodigious torque of an electric unit in a light weight car would push it along rather well :shock: I can't see it being cheap though, the technology is a bit new to come up on eBay etc. Have you looked into buying a motor yet?

Perhaps a retro fit hybrid unit will be the next big thing in the kit car world??

PEEPS - fantastic fabrication on the subframes, a real work of art. I'd love something like that for my Rossa2 but its way beyond my skills unfortunately....


Sat Jan 14, 2017 10:27 am
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