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MG Midget and Sprite Technical - Latest on LLW

Long time no posts!

I've been busy. Engine tweaked to 160bhp at Aldon (187 at local rolling road) at 7700 rpm.

New front brakes, new rear end with 4 bar link, watt linkage and coil overs.

Brand new stainless exhaust.

Car's an absolute riot and is mega quick, supple and lovely to drive. It's a bit peaky if you're used to something that has a torque peak at a sensible rpm (mine is at 6950) but is still great fun.


Rob Armstrong

Which engine would that be? Out of interest where did you mount the centre of the Watt linkage, on the body or the axle? Mine's fixed to the body.
David Billington

It's a 1600 rover K series. Watts is mounted on the axle, copying a number of other installs and most Escort versions.

I did think about mounting it to the shell, but decided not to to reduce variable roll moments.

When compared with the RTL I had (body mounted and large roll moment) the car corners flatter, is more controllable under power, and refuses to lift a front wheel under hard cornering
Rob Armstrong

"to to reduce variable roll moments" ???
I went for a centre mounted to the body to maintain a constant roll moment compared to axle mounted. I know many fix to the axle, Rover SD1 for example, but I saw another production car recently that had it fitted to the body but can't recall what is was at the moment.
David Billington

There are a few body mounted ones around. I wanted to keep the roll centre the same relative to the floor, rather than varying the roll centre with suspension travel. The cog moves around with the body though so yes, roll moment is now variable. Interestingly it rolls a lot less now than it did. With everything else the same, I took .6 seconds out of my pb at harewood.
Rob Armstrong

Now the Watt linkage is the sole lateral axle location you're pretty free to locate the RC where you want it, no leaf springs fighting your choice. Any pic of the axle mounting, did you have to reinforce the casing much?
David Billington

I've subsequently shortened the links to get the pivot vertical, but it's on the case slightly below centre of the axle


Rob Armstrong

Rob
Yep the higher roll centre explains why your front's are staying on the deck---curious, does it feel a bit taily/wheelspinny powering out of the turns like that.
William Revit

Do you have a weight for your car?
Daniel

Yes, a lot more oversteery. Easier to control, but definitely more tail happy.

Sadly no actual weight Daniel.
Rob Armstrong

Sounds like you're up to no good wanting weights Daniel.
William Revit

Rob, I see the underside of the car is more shiny then the upside LOL!!!
A de Best

You must have had fun welding that exhaust! Did a straight run under the axle foul on something?
AdrianR

Lol Arie. Yes, definitely nicer underneath than on top!

The exhaust hit the floor or the axle on full droop going underneath.

Rob Armstrong

I can confirm that it is quite oversteery 😂
Malcolm

G'day Malc. ,how're things going with you.

and Daniel
you asked about weights, my old hillclimber thing went 520kg and dead on 600 with me in it @ exactly 150 on each wheel---it's important to do your scaling with the driver onboard---my next car was going to be the magic 55% rear weight, but that's not happening now mostly because of rule changes at 'our hill'

willy
William Revit

Hi Willy,

Yeah, I'm alright thanks, you keeping well?

Rob and I were at one of the annual midget and Sprite Club days at a local sprint course a couple of weeks back. He kindly let me have a go and said along the lines of "it handles so well, if it starts to slide, keep your foot down and you will just do a god like power slide".

I got to turn three before lighting up the back end. I kept my foot down and was off backwards across the grass 😂

All good with my car, it's going strong, although I'm not using it much and not spending anytime in the garage either. House renovations and other life stuff getting in the way.

I picked up a Triumph 1300 engine a while back with the thought of making a full on race screamer engine. Shoot for 130hp! But that's a longer term project I haven't fully committed to yet. It would have to go in my car, which I'm a bit reluctant to do as right now it is so "perfect" as a useable every day fast road/occasional sprint car. I don't want to mess with it as well as make more new manifolds etc. as what's in there is all made to suit the 1500 making peak power in the mid 5s.
Malcolm

I'd put in a claim for false advertising if I was you Malc 😂 it is a little bit bitey sometimes

Rob Armstrong

All good here thanks Malcolm---
William Revit

Malcolm, you just have to buy another car!
Or you could even go daft and get an A30/35 saloon and fit your screamer 1300 in it.
GuyW

This thread was discussed between 18/07/2024 and 03/08/2024

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