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MG Midget and Sprite Technical - 5 link rear suspension

Haven't posted on here for a long time,but have continued to develop the turbo drag racing midget. Last Winter I fitted a 4 bar rear suspension with coilovers to improve traction on the strip. My aim was to bolt it up to existing leaf spring mountings plus a few extra bolt holes so I could revert if necessary. The coilovers were from gaz, and the mountings were made first in foamex,followed by laser cut plates, tacked together by me,then TIGed by someone who can weld. The bars were fabricated from tube with bungs in the end, RH and LH threads for ease of adjustment.
Initial testing showed the spring rates were too low for the torque on the strip so were increased to 300 lb/in. Otherwise it worked well with a new PB of 12.03 at 112 mph and 60ft time of 1.75 secs.


steve cowling

More pics


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and again


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one more


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finished


steve cowling

Interesting. Did you gain a bit of extra space for wider tires? Are you running a locked diff?
Trevor Jessie

Hi trevor, the car is jacked up to allow wider tyres under bubble arches. I run 8 inch drag slicks at the strip and yes there is a limited slip diff.
steve cowling

Wow, that's some impressive engenering & fabrication Steve!!
You may loose points in the car club on originality tho. ;)
Arie

Mm, you could be right Arie, even if they don't spot the turbo, chargecooler and nitrous...
steve cowling

Where does the top of the shock bolt to?
Onno K

Hi Onno, I bolted it to a 3mm thick plate which was bolted through the body above the axle,to another 3mm plate. This in turn was welded to a square section cross brace. Hard to describe in words, I'll post pictures when I'm back home in a few days. With this set up I managed to get the coilovers almost vertical.
steve cowling

Hi Onno, pic of coilover top mount. The coilovers have rod ends to allow for some misalignment.


steve cowling

And the support tube.


steve cowling

Looks great! Some similarities to my set up.


Nick Nakorn

Great minds think alike Nick! What rear suspension are you running?
steve cowling

Have you thought of making a 3-point link?

I'm looking at keeping the leaf-springs and putting a top-link from the top of the diff housing forward to the bulkhead immediately above the prop.

Should have similar benefits to the 4-link, but much less work.

(Use in conjunction with Panhard, Mumford or similar...)

This is a good vid to watch how 'live' is a leaf-sprung axle - this one already has a link to restrict sideways movement (a 1/2 length non-parallel Pan): https://www.youtube.com/watch?v=tN-4LLAKlpw

Anthony
Anthony Cutler

Hi Anthony, my reason for using the 4 bar was adjustment, pinion angle, amount of squat and preload on the offside. I tried an A frame bolted to the axle and the nose of the diff, located under the prop tunnel level with the front of the spring mounts, and this gave the weight transfer on launch, but some interesting rear steer problems mid track as the axle tried to pivot around the A frame front mount.
steve cowling

Anthonys link

http://www.youtube.com/watch?v=tN-4LLAKlpw

Steve... just an FYI, this BBS site has web standards as it relates to porn ...haha

Serious note... what tranny and what rear axle assembly... its certianly not a ribby 4 and the midget rear end...otherwise it would have a life expectancy of 1/16th of a mile

Prop
Prop and the Blackhole Midget

Good grief anthony,

That is a great vid, I had NO idea there was that much movement... 2:57my chin dropped on the floor

Im defiantly sticking a camrea on my rear axle to see what it does

Id love to see an overlay on top of this video of the gear, rpm, and mph and a video of the road ahead that would just be nuts

If you didnt belive in coil overs before you will now.

Thanks for posting that... agian, check with the web master on the use of porn here on the bbs...hahaha

Crazy and nice

Prop

Prop and the Blackhole Midget

Opps sorry fat fingers

The 1st ... ;20 to :50ish seconds ... not 2:57

Prop
Prop and the Blackhole Midget

Steve, I've been following this with avid interest. It's an awesome setup. I still don't understand all the implications, but it's giving me lots of fun thinking about it.

Anthony, that video is amazing. If I can fix my broken GoPro I'll try to make something similar. It will be a lot tamer though haha!
Greybeard

Steve, I have (as yet untested)a 4-link set up of my own design.
Nick Nakorn

Hi Prop, I'm running a Ford type 9 box with straight cut gears and hybrid axle using an English axle tube with atlas competition half shafts and side gears. I only use 4 gears on the strip,and with a 4.2 ratio and tall slicks I'm pulling 6500 revs at 112 mph.
Anthony that vid is excellent. At one point I tore the A frame almost in half,now I see why.
Ihave seen some time elapsed shots of my car on the strip as I shift,and the body roll as the torque comes off then on again is fierce, but on full boost plus the NOS it is making about 240 bhp at the wheels so I found I had to increase rear spring rates about 50 % to cope.
steve cowling

Steve... koutos, your the man !

Ive thought about your set up and couldnt figure out.how you were able.to hold.that drive line togather more then a few.feet.with the traction your putting on the concrete

Thanks.fr.the update...btw, becuase its a drag racer will you be upgrading to calipers from drums on the back ....

Just because you can accelrate to 115 in a quarter you still have to stop before the big wall in front...haha

Agian thanks for sharing that

Prop
Prop and the Blackhole Midget

Hi Nick,any pics of your setup?
Hi Prop,we have a long runoff area at the local strip...... I do have big discs and 4 pot alloy calliper son the front. The other thing that helps the trans is that he launch is soft to get the turbo spooling. So I slip the clutch with about 5000 rpm to get off the line. The NOS is on a wide open throttle switch,and I don't hit that until I'm in second. The car is struggling for traction even on 8 in drag slicks.
steve cowling

The car is struggling for traction even on 8 in drag slicks.

Factory 63 HP can do that :-)

Prop
Prop and the Blackhole Midget

Steve, sorry, no can do... I was very open about my project a while ago (much nicer)and by accident, via photo I posted, was copied in on a FB conversation between two guys discussing how to copy the design. I had two worries; a)that the untested design my have flaws that would be dangerous (unlikely but you only get to find out when things go wrong)and b)I didn't want the quality of the design (and my reputation, if the car is a success) to be compromised with poor copies if I were to decide to market it as a kit. So I have held back many details since then. I have a private family and friends website with films of the project's progress that will be posted on a public site after the launch of the car. The car will be finished this year and launched next summer to give me time for testing. Meanwhile, some info is available on an unsecured at

http://www.nagaramg.tumblr.com

But I've not been telling many about that very much either because progress is slow - I have numerous health issues so I have to go at a pace I can manage.

But I'd be very happy for all the folks here to take a look at the public site - all constructive criticism very welcome! :-)
Nick Nakorn

Nick,

just a cheap easy tip for copyright protection

I photo everything and take all my orginal drawings and notes and date them at the post office with there dated cancelation stamp then I seal it in an sealed envolop and have the post office stamp the flap edge of the envolop with the cancellation stamp then in a court of law a judge would open the envolop and the material is all dated with offical gov stamp cancellation proving the dates of your R&D

Prop
Prop and the Blackhole Midget

Prop,
Yes, many thanks for that. But I looked into that a while ago and none of my work is sufficiently novel to warrant protection under patent law and very few suits are won trying to protect 'original design' if the design is a variation on what has become generic. All digital photos are time-stamped anyway. But thanks, it's good advice and I've done that in the past myself prior to the digital age!
Nick Nakorn

Of course the trouble with patent law is that it only gives you the right to defend it at your expense and these days it is thought that the patent has to be worth many millions of £s to make it worthwhile trying to defend it. In some case where a process is developed it is better to keep the details secret, Bessemer (of converter fame) made his first fortune with a process to produce powdered brass or bronze for gold coloured ink and kept the details sceret or a couple of decades IIRC, not really an option though for a suspension design.
David Billington

David, indeed. A 4-link is not at all new and my design is really all about refining the geometry.
Nick Nakorn

This thread was discussed between 06/07/2015 and 17/07/2015

MG Midget and Sprite Technical index

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