xpensive wrote:A question for you JT, or anyone else for that matter, I would like to try some realistic numbers on a front upright,
with two "angular contact ball bearings" in an arrangement like this;
The image shows an X-arrangement with the 40 degree contact-lines intersecting, while we would probably prefer the reverse, an O-arrangement. But what would a reasonable inner/outer diameter, and distance between them back-to-back, of the bearings for an F1 car be?
Also, if anyone can help me with a suggested load-case?
No takers on that one, perhaps a little too geeky for this forum? scarbs?
"I spent most of my money on wine and women...I wasted the rest"
That arrangement of angular contact ball bearings is probably not optimum for a race car upright. Normally, the upright bearings will not carry equal loads, since they are not equally offset from the load. Statically, the outer bearing will see a larger moment force since it has a smaller offset to the tire contact zone.
But you must also consider dynamic loads. The instantaneous load direction and magnitudes on the bearing set can vary significantly due to aero downloads and cornering forces. Additionally, the type of race circuit must also be considered. A champ car on a high-speed oval track will produce substantially higher bearing loads on the outside suspension than the inside suspension.
As for the suitability of your 40deg angular contact ball bearing set, those contact angles are probably a bit too steep. The moment load capability of a duplex angular contact ball bearing set is established by the spacing of the intersection of the ball contact axes and the axis of rotation. So that back-to-back arrangement would have more moment capacity than a face-to-face arrangement. But like most things, there is a trade-off between radial and moment load capacity, as well as friction loss, with increasing contact angle.
Finally, besides contact angle of each bearing, you must also carefully consider preload. Since preload will affect the instantaneous contact angles, load distribution, performance and efficiencies of the bearings in service. A duplex angular contact ball bearing set will give the best efficiency and least problems with deflections in the shaft or housing structure. A set of tapered rollers will give better load capacity and will be lighter and more compact, but will be less efficient and less tolerant of misalignment. And a combination of a cylindrical roller outer and a 4-point ball inner would be a compromise between the two.
Hope that helps.
Regards,
riff_raff
"Q: How do you make a small fortune in racing?
A: Start with a large one!"
Thanx riff, but without a loadcase with numerical values it is difficult to judge the different arrangements.
Which arr. is preferred in F1 today anyway, scarbs?
"I spent most of my money on wine and women...I wasted the rest"
I'm sure F1 uprights use a duplex angular contact ball bearing set, since their chassis are light and their axle loads are fairly low. The duplex ball bearing set would give them the best efficiency and would be least affected by the local thermal environment produced by the CRC brakes. Take a look at this company's hybrid bearings:
Thanx Terry,
That's what I suspected, see the SKF layout. Imagined a bit of spacing between them though for loadbearing reasons,
but a matched pair makes preload much easier of course.
"I spent most of my money on wine and women...I wasted the rest"
Since you guys said these are duplex, the other set of rolling elements are on the backside right?
They say this one has a high performance plastic cage. Which I guess enables finer shaping of surfaces that keeps the balls since plastic is more formable? Very interesting.
Difficult to say, depends if an O- of X-arr, but the piece on top probably doesn't belong, that's a needle-bearing of sorts.
A composite cage (usually glass fibre/PA66) has different advantages vs steel or brass, weight being the obvious one,
but since one of the features of hybrids is ability to run without ideal lube conditions, I should think the choice of
material has something to do with the latter as well.
"I spent most of my money on wine and women...I wasted the rest"
The ball and roller bearings in that photo are obviously not a matched set. Angular contact ball bearings must be used in opposing pairs, due to the fact that an angular contact ball bearing can only handle thrust loads in one direction. If that angular contact ball bearing was combined with the roller bearing shown in the picture, on a race car stub axel, the wheel/tire would simply separate from the upright. Since the roller bearing would provide no axial constraint in opposition to the angular contact ball bearing.
As for preload, you can't easily preload a cylindrical roller bearing. But apparently, the angular contact ball bearing has an outer race that uses screw threads to set its axial preload.
As for the cages, they're probably silver plated alloy steel, and not some polymer like Torlon or Vespel. High performance bearings can have very high cage stresses, which may require something stronger than plastic.
Regards,
riff raff
"Q: How do you make a small fortune in racing?
A: Start with a large one!"
I would perhaps not recommend trying to decide the preload of two angular contact ball bearings with a thread like that.
What you typically do, is trust the tolerances of the raceways to give you the proper preload when mounted back-to-back.
As for the cages, I have never seen a machined steel-cage like the one above, brass yes, but not alloy.
As before, Nylon(PA66)/glass fibre composite is a popular choice on hybrids for the ability of next to dry-running.
The ball and roller bearings in that photo are obviously not a matched set. Angular contact ball bearings must be used in opposing pairs, due to the fact that an angular contact ball bearing can only handle thrust loads in one direction. If that angular contact ball bearing was combined with the roller bearing shown in the picture, on a race car stub axel, the wheel/tire would simply separate from the upright. Since the roller bearing would provide no axial constraint in opposition to the angular contact ball bearing.
As for preload, you can't easily preload a cylindrical roller bearing. But apparently, the angular contact ball bearing has an outer race that uses screw threads to set its axial preload.
As for the cages, they're probably silver plated alloy steel, and not some polymer like Torlon or Vespel. High performance bearings can have very high cage stresses, which may require something stronger than plastic.
Regards,
riff raff
Thanks.. though I didn't mean to draw attention to the cylindrical roller bearing.
I found an article with similar views on ceramic bearings.
The advantages of the ceramic seem to be strengthened even more in a harsh chemical environment such as seen when used in marine vehicles:
I am part of the Nottingham University Formula Student Team 2011. I have the task of redesigning the front and rear uprights for the single seater ~230Kg race car powered by a Yamaha R6 600cc motorbike engine. Due to limited funding and resources, I have to utilize the same pick-up points for both the suspension wishbone arms and steering (front) and bump steer (rear) tie rods. I was wondering if anyone could offer advice on potential design solutions or links to useful literature.
Ahh yes.. a popular topic. Uprights are surprisingly straightforward.
1. You have the suspension points set? Put some material in those areas.
2. Should be pretty easy to estimate the max vertical and lateral force the tires are going to see, along with a general idea for tire radius. Use this to spec what size bearings you'll use and how far they'll be spaced. Put a ring of material in to hold the bearings.
3. Have the brake guy spec the rotor size and caliper type, and that should locate the caliper mount points. Put some material there.
4. Fill in everything in between keeping DFM in mind.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.
Jersey Tom wrote:Ahh yes.. a popular topic. Uprights are surprisingly straightforward.
1...
Put some material in those areas.
2...
Put a ring of material in to hold the bearings.
3...
Put some material there.
4...
Fill in everything in between keeping DFM in mind.
Good to see you back to your usual specific self, JT.
"I spent most of my money on wine and women...I wasted the rest"
I'm not gonna walk the kid step by step through the design process. Gotta do some work on their own.
At a high level, that's all there is to it (I've designed my fair share of these damn parts, and I think any other FSAE grad would agree on this). Establish your geometric and functional constraints... and really the rest just falls into place. Figure out how to smartly put material between your functional elements to maximize stiffness, minimize weight, and minimize how much the machinist is going to yell at you for an asinine design.
Grip is a four letter word. All opinions are my own and not those of current or previous employers.
