Suspension uprights?

[mep]

Next I want to do is apply brake torque which brings me to my question, how much torque should I apply? I was thinking something around 1500Nm. Is that a good number for a car that weighs about 1200kg?

No, after a very short calculation I would say you need at least something around 2700 Nm (better more).
To give a better statement we will need more informations about the car.
At least I do, maybe there is somebody else around who can tell you the needed torque just by experience.

Anyway how much brake acceleration do you expect?
Does your car has any kind of downforce?
Tyre diameter?
Longitudinal center of gravity location and height?
How much torque does your engine produce?
You should be able to stall the engine with your brakes. This means your brakes must have more torque than your engine.

[Jersey Tom]

Yes I know My target handling limit is 1.5G anyway but I just wanted to see what happens @ 4g´s.

FOS of 7,7 at 1,5 g´s cornering but when I add brake torque of 1500Nm the factor of safety drops to 1,1. However cornering and braking at the limit at the same time is unlikely to happen anyway, besides I don´t even know if the brake torque is even near to the realworld force

You should be able to get a good idea for real braking torque with the vehicle weight.. rough CG height (axle height?).. wheelbase.. and COF.

Also make sure you're applying the braking load correctly.

[tomislavp4]

I got a value for the braking torque, it is close to 4000Nm. I also changed the material from 6063 to 7075. The FOS with combined 1.5G´s and the braking torque is 1.5 and the thing weighs 2.5kg Time to get to work and remove some Al

[PlatinumZealot]

4g braking.. if your car weighs 1200Kg that is about 48000N of braking force for all 4 wheels. Proportion it to each wheel. E.g 20,000N braking force at the back tyres and 28000N at the front. So each back tyre is producing 10,000N braking force. Just multiply by the wheel radius for the brake torque. 10000*.33= 3300Nm.

If you want the force at the brake mount you divide the wheel radius by the brake mount radius, say 330mm/150mm = 2.2 and multiply this by the Braking force at the tyres to get the friction force at the mount = 22000N.

It was useful to manipulate the torque into a force because the torque from the brakes is counteracted by the upright via the mounting bolts, the bolts mostly experience a tangential shearing force from the torque instead of the torque it self.

edit: Oh never mind you found it.. close too.. hehe

[tomislavp4]

Haha beat you by a couple of seconds didn´t I Thanks for the help guys

[Jersey Tom]

But you won't be braking at anywhere near 4G... poor design to start with completely unrealistic assumptions, no?

[tomislavp4]

Combined wheel force at 2g braking: 2*9,82*1200=23568N I have 3 wheels and under the assumption that the front tires do 40% of the braking each I get 9427N per wheel. That multiplied by the wheel radius gives close to 3000N, not far off what I used in the FEA simulation

It is too much I agree, I will reduce it and see what happens than.

[marcush.]

just found some pics of the Doran Racing ford GT .machined upright and nsmikle type aluminium wishbones ..:

http://www.angerole.com/Photos/Blog%20S ... ension.jpg


http://www.angerole.com/

[xpensive]

Xcuse me for barging in like this, but I was going through the early posts on this thread and came across scarbs' comments on bearings, which cought my interest when I work with roller-bearings and their applications for a living.

I have to say I was surprised to learn about the use of hybrid-bearings for the uprights, when such are primarily used for the following purposes;

- Xtreme Rpm's.
- Electrical insulation.
- Xtreme stiffness.
- Oil-free lubrication.

None of the above conditions really apply here, why my only conclusion is that it is the lower mass of the rollers (-40%) that justifies the xorbitant cost of these bearings?

[marcush.]

Xcuse me for barging in like this, but I was going through the early posts on this thread and came across scarbs' comments on bearings, which cought my interest when I work with roller-bearings and their applications for a living.

I have to say I was surprised to learn about the use of hybrid-bearings for the uprights, when such are primarily used for the following purposes;

- Xtreme Rpm's.
- Electrical insulation.
- Xtreme stiffness.
- Oil-free lubrication.

None of the above conditions really apply here, why my only conclusion is that it is the lower mass of the rollers (-40%) that justifies the xorbitant cost of these bearings?

stiffness is a very important feature but :
you forgot the extreme temps caused by the carbonbrakes....they had a lot of troble with wheelbearings before ceramics..
I thought F1 was using full cermic bearings on the wheels already...

[xpensive]

Probably goes under "Lubrication" features then. Wonder if DLC-coating (Diamond Like Carbon) of the rollers been tried?

[PlatinumZealot]

Here is a nice picture

[marcush.]

Probably goes under "Lubrication" features then. Wonder if DLC-coating (Diamond Like Carbon) of the rollers been tried?

sure this is the poor mans solution ..

http://www.oerlikon.com/ecomaXL/index.p ... r_bearings

works .

if you happen to choose a bearing that can be put to pieces without damage there is the possibility to have the parts
coated at Balzers ,they do have prototype coating services available.Still deep pocket necessary at around 5€ per piece coated....

[riff_raff]

xpensive,

The bearings in an F1 upright have been hybrids for quite a while. Normally they are SiC rolling elements and M50 steel races. SiC is also used for the CV joints. It's all for reasons of weight savings. But the weight savings with SiC comes at a high cost: about $600 per pound.

The downside to hybrid bearings is that they have lower load capacity than a comparable all steel bearing.

Regards,
Terry

[xpensive]

Thanx Terry, but don't get me wrong, I have worked with hybrid bearings in electrical machinery on a number of occations, but for reasons of Rpm and electrical insulation, not due to weight-savings.
Heck, a 40/80 mm angular contact bearing from steel is 370 grams, of which the rollers are the smaller part, why this makes the savings from 8 hybrid bearings perhaps half a kg? But everythng counts I guess, Christ...