Front Subframe

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Front Subframe

Postby Alan D. » Sat Mar 18, 2017 9:47 am

I'm trying to make a Mk1 comfortable and reasonably quite for long distance travel. There was a lot of vibration inside the car, with the instrument needles bouncing up and down. I've changed the engine mountings and this has certainly helped.
I'm now looking at the front subframe mountings, on this car the subframe is bolted directly to the fiberglass both front and back. Is this normal? I've purchased new mounts and was just blindly going ahead to fit them. The front teardrop mounts would be no problem, as I would just manufacture brackets to suit what ever position the ended up.
The rear mounts to the floor have more implications if I add them. I would be move the subframe down and forward slightly, moving the axle line, down and forward, possibly giving more wheel clearance, stopping the tyre contacting the rear of the wheel arch. The other challenge is how will this impact on the tower bolt connection, will I have to put a spacer between the top of the subframe tower and the bulkhead cross member?
I also have the small replacement coil springs to fit in place of the rubber cones, but I will report on this after I've fitted them next week hopefully.
The engine mounts I purchased were the ones with the Rivnuts fitted to them, My advice is don't use these ones as they created allsorts of work. The supplied bolts were tight in the threads, which made the Rivnuts spin. I had to remove them, tack weld the Rivnuts and tap them out to 8 X 1.25 and fitted them with stainless bolts. But I got there in the end, after much cursing!
A better solution which I used years ago is to weld nuts on to the standard engine mounts. I'm also interest on any ones thoughts on adjustable front shock absorbers, As the ones fitted to the car will be at least 37 years old.
Alan D.
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Re: Front Subframe

Postby ACourtney » Sat Mar 18, 2017 10:24 am

If you want the least vibration then fit the subframe with rubber bushes or poly bushes that are "road" hardness. The Midas was designed to have the original rubber mounts fitted, they reduce the noise and vibration going into the shell. A compromise would be uprated poly bushes. The only problem with poly-bushes is that there are now so many different ones available and many of the vendors don't know if their "uprated" bushes are stiffer than the standard rubber ones, or simply called "uprated" because they are polyurethane. My preference is for Powerflex who use a simple colour coding system for the different hardnesses.

Fitting the subframe directly to the shell will remove some compliance, which will help steering accuracy - the Mk1 and Mk2 have the rack fitted to the shell, so any movement between shell and subframe will introduce unwanted steering inputs. However, I would think that with brand new bushes you won't notice anything through the steering.

There should be a pair of bushes used on each the tower bolt. The lower one is diamond shaped and sits between the subframe and body.

I'll be interested to learn how you get on with the springs, as I'm sure will be many Mk1 and Mk2 owners. I don't have any experience with adjustable shocks to pass on, other than to say if you are going to springs then you are going to need to fine tune the damping to match. It might be worth looking on a Mini forum to see what has been used with front springs. The front axle weight of a Midas is about the same as a Mini, the Midas saves the weight at the back end.
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Re: Front Subframe

Postby Stuart » Sat Mar 18, 2017 10:32 am

I wonder is it a modified early two bolt subframe? and when you say front and back are you talking about just the front subframe?
Certainly there is more noise from the rear frame than compared to a mk3 with its rubber mountings, but fitting some sort of rubber mounts at the rear could get quite complicated.

I have these on my car https://www.minispares.com/product/Classic/552018.aspx seemed just fine although I didn't do many miles in the car.

Guessing you don't have the car with you in Carlisle to take some photos?
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Re: Front Subframe

Postby Alan D. » Sun Mar 19, 2017 8:45 am

Thanks to both Alistair and Stuart,
Ever helpful and informative. I'm going to fit the little springs this week and hopefully fit to the front subframe, the new front and rear subframe standard rubber mounts. I'll report back when I've done the job.
The other thoughts I've had on front subframe fitting is about the tower bolt holes. I read somewhere that these holes in the fiberglass cross member can get elongated, due to subframe movement. I thought I could get some stainless steel plates made to act as flange fitted on top of the fiberglass cross member and the tower bolt could pass through that flange (pop riveted to the top of the cross member ), I could also add a sleeve welded to this flange, for the tower bolt to pass through. Hopefully this would help with subframe location and stiffness. Or am I just embarking on another over- engineering project?
This comes from an apprenticeship building cranes.
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Re: Front Subframe

Postby ACourtney » Sun Mar 19, 2017 10:55 am

Hi Alan,

If the holes get elongated then surely you would want to look at repairing the underside of the bulkhead first as that is where they locate so if the wholes have opened out there it will allow movement. If the subframe has been fitted without any rubbers then I can believe that the subframe could chafe away at the GRP of the bulkhead and open out the holes. The holes at the bottom of the bulkhead are the ones that are important for subframe alignment. The holes in the top surface are less important, but the tower bolts will act as a pillar slide in their rubber bushes, so they still have a role in the alignment of the subframe.

I would wait until you have the rubbers and then see how well they fit into the holes. Then offer up the subframe (easiest with a bare subframe) to see how well the turret mounts align. If the holes have been worn away then it is worth thinking about how best to repair them. If the rubbers between the subframe and bulkhead are a good tight fit then you don't need to worry

The GRP is very thick on both the top and the underside of the bulkhead, unsurprisingly. Some models of the Mini Marcos (perhaps all, but I've only looked at a few) use the steel panels from the Mini to form the bulkhead, but that has its own inherent issues.

If you do need to repair any of the holes then I wouldn't worry about a reinforcing plate as the bulkhead is plenty strong. However, you might find it easier to open out the hole and bond in a metal collar, rather than trying to make a composite repair. Metal collars would be much harder wearing and could be bonded in place using the subframe and tower bolts to align them correctly. If you have access to a lathe then it would be easy to turn up a suitable collar in something like brass that won't corrode and bonds easily.
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Re: Front Subframe

Postby Stuart » Sun Mar 19, 2017 11:01 am

Yes don't get carried way I'd say Alan. The rubber can abrade the GRP a little at big mileages.

oh and for a much more comprehensive answer see Alistair's post

Any photos of this car please?
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Re: Front Subframe

Postby Alan D. » Sun Mar 19, 2017 7:48 pm

Thanks again to Stuart and Alistair, I think you both constitute the encyclopaedia Midas.
Stuart, picture will follow, the car is MOT'ed , so just trying to get back on the road. It seems to have an excellent engine and mechanics, the gearbox is out of the Cubman GT, with a higher 1st gear and a close ratio 2nd & 3rd, with a 3.7 diff. But the body needs refurbished, it got a few stress cracks and the usual faded red paintwork. I just wonder why it has done so few miles in its 37 years (27000). I have only driven it on to the trailer. I'm guessing it's noisy and uncomfortable.
I think the sun roof has been leaking and destroyed the carpets and interior. The interior would not have been to the same standard as the mechanics. It's been easy to dismantle as every nut and bolt has been greased! Going to order an Allspeed subframe soon.
The sunroof seems to be a standard item across the Midas range, I don't know the brand name as yet, as it is way down the list of jobs, but I wonder if new rubber seals are available? Ultimately I would like to fill the sun roof in, ( as per Alistair's instructions, somewhere on this board) when I get over my fear of working with fiberglass!
I've ordered five sets of laser cut plates, to make rear beams, so hopefully this Midas will be the first Midas with adjustable rear suspension.

Thanks again to both of you.
Alan
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Re: Front Subframe

Postby Stuart » Sun Mar 19, 2017 8:28 pm

Ventalite was Harold's sunroof of choice, with a 1 year guarantee you're sadly well outside that period :P

Allspeed :o which engine are you going for I wonder?

two prices from the brochure just to highlight how electronic goods have come down in price.

Pioneer KC5800 £195
Laminated windscreen £30
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Re: Front Subframe

Postby Alan D. » Sun Mar 19, 2017 8:54 pm

SUZUKI
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Re: Front Subframe

Postby Stuart » Sun Mar 19, 2017 9:08 pm

Alan D. wrote:SUZUKI


3 or 4 cylinders ?

Can't you just slot this subframe in?

3-cylinder.jpg
3-cylinder.jpg (419.53 KiB) Viewed 8681 times
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