OMS 2000M Underbody aero

[Clive Austin]

Agree with the point on flexing Craig. This would need to be sorted out but shouldn't be too difficult. Also, the rigid fixing to a fully sprung part of the chassis answers one question - ie the idea of an aerofoil fixed to the wishbone itself to move with it is a none starter. Putting a fixed aero profile in the tunnel to screen the wishbone should still be OK though and might help with the bracing.

[robcapper]

I took nearly 20kg out of the already feather weight nemesis. Get rid of the pods; you don't need them. Fit a straight exhaust, tiny rad, minimal hoses (and therefore water) cut away tubes that dont need to be there, get a lighter tank, get a smaller battery & stick it under the seat, make a mould of the bodywork & make single skin versions, fit a decent floor & wind down the wing.
Nemesis currently approx 265kg. The new car (1100cc) will be less than that.

[Clive Austin]

It would be interesting to weigh the car whilst I've got all the body work off. Anyone know how? Don't really want to buy 4 sets of scales that I will only use once though. I have an hoist that list the whole car via the roll hoop so some for of strain guage would be ideal.

[sevaun]

Originally Posted by Clive Austin

It would be interesting to weigh the car whilst I've got all the body work off. Anyone know how? Don't really want to buy 4 sets of scales that I will only use once though. I have an hoist that list the whole car via the roll hoop so some for of strain guage would be ideal.

Clive i would suggest doing it corner by corner:

Put bathroom scales under one corner and pack up other three corners to level the chassis. Read off the weight then repeat for other three corners. The sum of all four readings should be your total weight if I'm not mistaken, although others with more knowledge than me might correct me on this.

Richard

[Steve Wilkinson]

I would have thought that removal of the sidepods might be OK if all you did was hillclimbing. However I would also conclude that the sidepods will be worth keeping as they will work well on the longer sprints such as Aintree & Anglesey (might not be that effective at places like Three Sisters).

[andylaurence]

I bought 4 bathroom scales from Sainsbury's. They weigh up to 130kg each and cost £20 for the set. They're analogue (not electronic), so you don't need to worry about tapping to turn them on and then settling the car in time. I must weigh the car over the winter to see just how much I've pulled out of it. There's been a good bit of non-essential wiring, 2.5kg of bodywork and redundant bracketry a few weeks back, not to mention 5kg for swapping from a lead acid Red Top battery to a lithium pack (600g).

If you have 200kg of downforce, it's more effective on a 200kg car than a 400kg car. Lose weight and you can lose some downforce, which reduces drag and makes you faster on the straight bits even without the extra acceleration you'll get from less weight.

[Rob Way]

Hi Clive

Fyi the tunnels don't actually make any down force it's the transition from the flat floor to the tunnel that creates the low pressure and the down force, the purpose of the tunnels is to slow the air down as it is integrated back into the airflow behind the car. The trick is to get the angle right so the air doesn't detach at the transition point, you can test this by using food die in engine oil run along the edge where the flat floor ends. You are looking for the oil to run up the tunnel in straight lines.

The wishbones passing through the tunnels will create a bit of turbulence but wont have any detrimental affect on the ultimate down force.

I note from the picture that the transition point is at the side pod thereby creating your low pressure point in the middle of the car. I would add a second diffuser at the back of the car under the rear wing as I did on the jedi creating a second low pressure area right at the back of the chassis, you will then be able to reduce your rear wing. Designs can be found on the web, or if you take measurements I can get dad to make you one.

I have loads of other small things you can do as well but I need to draw you some pictures to explain.

Wikipedia explanation http://en.wikipedia.org/wiki/Diffuser_(automotive)

Much better than my explanation.

Hope that helps. (I've been spending waay to much time with F1 aero engineers, I'm starting to bore myself)

Rob

[Clive Austin]

With you on the aero Rob. It's all about the smooth transition between regions of static and dynamic pressures. Agree also on the angle but if the diffuser is moved back far enough it should work better with the rear wing. This then allows more angle to be used before the airflow detaches and becomes turbulent. Sketches, pics and ideas would be gratefully received I think you've got my email but PM if not. Much appreciated.

Saw Colin at Curborough btw. He had a bit of damage to the front but hopefully not to hard to fix. Looking forward to the new blue tyre covers too - the black ones have been a God send.

Cheers

C

[andylaurence]

Rather than moving back the diffuser, can you not extend it for interaction with the rear wing? You don't have to run such an aggressive angle to get it close to the rear wing in that case and the CoP will stay further forwards. If it's taller thanks to the same angle and longer length, you might be able to drive it with some clean air from the back of the side pods too.

[Clive Austin]

Actually Andy, that's what I meant - although not what I typed! There is some logic to just moving it back though - namely is gives a larger area of low pressure and hence more downforce (all other things being equal), moving the CP back might suit the car given it's new front end design and pushing the start of the tunnels further back might mean there was more chance of squeezing them under the rear wishbones. However, even then I don't think they will fit on the 2000M - hence the idea of an aero shroud and gaiter. Then an extension on top of this - less angle and greater rear wing interaction as you say.

C