Uni work - Brake assembly done

23rd November 2012, 00:05

Thought i'd post up my uni work in engineering, thought it may be of interest to people in this section.
It's an upright i designed last year for a formula student race car.
This year i am designing and optimising the hub assembly, but that's a work in progress.

23rd November 2012, 13:30

Nice mate

23rd November 2012, 13:49

Looks good which uni?

23rd November 2012, 17:20

Cheers, Brighton

23rd November 2012, 18:31

Sweet, we got pushed over onto Catia now for some reason for final year.

23rd November 2012, 22:48

I really want to get some hours on catia. Its what i'll be using in industry, but its just too dam expensive to get a load of licences for uni computers.

27th November 2012, 16:49

Looks mint that mate!

I've done a very similar thing within Solidworks but designing the unequal A arms and hub assembly for our SAE car (LJMU). Currently completing a project with FEA to optimise a piston including removing as much material as possible but keep the structural integrity and principal stress distributions the same.

What year you in? I'm half way through my final year project (although I'm doing a masters so another year to go yet) on simulating a FSAE car and comparing the results to data logged information. Still trying to get my model up and running to give tyre loadings within 5% of the calculated loadings. Its a right bitch to get close though haha!

27th November 2012, 18:54

Quote:

Originally Posted by adamskiTNR

I really want to get some hours on catia. Its what i'll be using in industry, but its just too dam expensive to get a load of licences for uni computers.

Catia is alot better imo for the basic creation of designs and making parts/assemblies/cutter paths etc however i still prefer SW for FEA etc and ive also had some issues transfering models from catia to SW which is abit gash.

28th November 2012, 00:00

can you do all my cad work for my assignment?

I'll pay you in massages.

Happy endings included.

28th November 2012, 01:18

In my second year at the moment. Best of luck with tyre modelling. I haven't tried it myself, but seen the calc's and vehicle models with them in and anything slightly dynamic is just a massive ball ache

28th March 2013, 19:15

Okey dokey. Got my initial hub built up with bearings preload spacer etc. It is a slightly unconventional design, as it uses a face spline as retention for all 6 DOF's. Thought i may as well jump at it and see what i can design this way. This shows the first draft of the face, though i haven't finalised/decided on the rear hub fixing yet.

29th March 2013, 08:38

what is dof ,looks more like a ramp from an lsd

29th March 2013, 11:05

Directions of freedom

29th March 2013, 11:30

Te problem i have is that standard centre lock systems are shit. The compliance in the system is huge. And they fret badly.
A face spline sorts all the issues, but creates new ones, such as the braking force now adds load longitudinally to the wheel nut. Would still be easy to revert to a standard drive peg design.

31st March 2013, 11:51

ah, so its a drive flange to mount the road wheel on with single center nut fixing.
the main problem with centre fixing is the amount of expansion in the hub you have to allow for with the heat from brakes ,which is why the they have to be a loose fit ,but clamp up well.
looks like it should work ,not usre how the flat faces will cnetralise the wheel --maybe same basic shape but with tapered flats to cnetralise the wheel and not rely on tight fit on centre post and with a flat bal race built into the wheel nut between the taper and the nut to reduce frivtion ,so clamping troque is real value

31st March 2013, 19:31

The wheel will not touch the central shaft. The faces are tapered downwards and towards each other to centralise. This also prevents the problem with expansion as the clamping will remain pretty constant from the flat faced wheel nut, and the flange face will remain constant. The point is that no part of the wheel will be touching the flat faces or the bottom of the grooves. So that the taper effect doesn't bottom out

3rd April 2013, 03:19

*Dramatic reveal music* It's complete!... well... the initial draft is. I still need to run numerous stress tests on the components.
As you can see in the picture it uses a large rear plate to fix the frontal section into place. This plate has been the bane of my life. Running test after test to try and get it to hold the clamping force (31500N over a 24mm diameter area.) Not pleasant numbers. This clamping force is so high compared to some of the other loads the hub will experience, but is often overlooked as just "bolting the thing together". I am happy to get it into aluminium form eventually. It was alu, then it broke, i made it thicker, it broke. So i went to steel, it broke, i made it thicker, it worked! But by now was 162g (the main hub component is 212g!) So i changed the design completely. It is now a nice 63g part. I have the option of this design in alu, or a nice thinner design in titanium 4v, but that stuff isn't cheap so aluminium it is.
It should be interesting to see how the braking forces will vector from the angled faces of the hub, be it good or bad.

4th April 2013, 00:57

Have you had any problems with the ball roller bearings being spaced apart such as a high breaking force... Because the bearings have a pre load spacer in there setting them apart the outer will take much much more of a beating due to the leverage effect and the pivot point witch would be the rear bearing... Again the same problem with high cornering speeds it will want to push the center of the bearings through... Have you though about tapered needle rollers?

It was just a though

4th April 2013, 02:32

Don't worry, I have the actual bearings in the cad model now, you cant see them in these pics as they are just config parts. The bearings are a paired set of deep groove angular contact bearings, so only work in one direction. Similar to a taper setup, but without the assembly limitations.

4th April 2013, 02:33

But yes the outer bearing will see more loading being the fulcrum, but is unavoidable. They will be lifed as such.
an example http://www.scots-bearings.co.uk/file...ll-bearing.jpg

4th April 2013, 08:39

I take it you have gone 2 bearings rather than a single pre spaced unit for weight saving,

4th April 2013, 14:31

I could probably have made a lighter overall design by using a smaller, wider single bearing. But the main concept of the upright is that it can be used on both the right and left hand side without needing any design changes to save on manufacturing costs and time. This requires such a bearing design. The 2 bearing setup is also much nicer to assemble and take apart.

4th April 2013, 14:51

no reason why it still couldn,t be suitable forall 4 corners --circlips in both sides and a good press fit (warm up housing to fit bearing) --it ain,t going anywhere if you use brg fit as well

4th April 2013, 15:02

I'm not a huge fan of press fits, especially into aluminium. I like to be able to assemble and disassemble race car parts without feeling like i'm fatiguing and wearing the parts in the process. And like this you can take it apart at the event if need be, without the need for a press. And adding a circlip on both sides will require the bearing to be set further into the upright and so increase the moment created by tyre side loads.

4th April 2013, 15:59

Better shot of the angular contact bearings.

4th April 2013, 16:10

looks good matey, is this for your diss?

4th April 2013, 16:59

No, just my second year project. did the upright in my first year. I'm thinking about doing something more ground breaking for my dissertation, maybe integration of electric drivetrains, not sure yet

7th April 2013, 01:44

Cut away picture of the (provisonally) completed design.
The blue element is a stand in component for the centre of the wheel.

8th April 2013, 08:55

Quote:

Originally Posted by adamskiTNR

I'm not a huge fan of press fits, especially into aluminium. I like to be able to assemble and disassemble race car parts without feeling like i'm fatiguing and wearing the parts in the process. And like this you can take it apart at the event if need be, without the need for a press. And adding a circlip on both sides will require the bearing to be set further into the upright and so increase the moment created by tyre side loads.

even with your 2 bearings you still need an interference fit for casings .
and if you make internal hub the size correctly warming uprgiht to 130c max will make the bearing a slide fit ,or just a light press fit which will not damge the upright . or even put bearing in freezer before fitting .
a 1or 2thou interfernece fit is all that is needed ,even looser if you use modern brg fit adhesive
it is a very common way of assembly for close fitting parts
tthe extra "moment" will be very small and the life of a correct preloaded bearing will be a long time in racing terms ,certaintly alot more than a single race season .
far more likely to have a corner knocked off the car than having to change a bearing and being able to use it on all corners must make spares holding +manufacture cheaper .I would have thought that thinking that way would win you "brownie" ponits as well for simplicity

8th April 2013, 14:09

The bearing and hub, as well as bearing to upright are both close interference fits. (I cant remember the engineering jargon code for the tolerance).
Yeah I've used 4 cans of aerosols in a 24hr race to cool a bearing down for fitting lol.

8th April 2013, 14:11

Really expensive bearings are nice to work around though. As these bearings are toleranced to microns. So the tolerance of the fitting component is all you need to worry about in the design.

8th April 2013, 14:54

not sure how you go about working out the differential expansion rates of the alloy uprught to the 2 indivual brgs and the alloy inbetween them --,never mind the through bolt that keeps the load on them .
a single double row brg with intergral preload spacer must be be far more dimensional stable --maybe that why in your 24hr race bearings failed --preload changed .
you don,t need to know accuratly the preload to tighten the through bolt to with double row --as its not so critical to get the preload on the bolt correct --just up tight and spacer in brg wil give you correct preload

8th April 2013, 15:06

The 24hr bearing was a full ceramic porsche 911 rsr single wheel bearing.
And yes that's the idea. The preload spacer being exactly that. the width of it being the variable for bearing preload.
And the expansion is a tricky component of this design. As you can see in the images the material around the bearing carrier seems very thick. It is indeed thicker than it needs to be for structural reasons. The idea being that the exterior of the upright is cooler than the material around the bearing. This "should" force the thermal expansion to contract around the bearing than the entire upright "scaling" outwards, if that makes any sense. As you can imagine this is where race teams with lots of money and resources can shave weight off while keeping the thermal expansion under control. I just dont have the time to run that many simulations.

8th April 2013, 15:58

I could be wrong --but my guess would be that most of the heat comes from the brakes etc ,into the flange then into the hub .and not from the brg outwards.

single seater has no mudgaurds or wheel archs like the porsche or the weight ,so heat build up should a lot less from brakes etc than a "tin top" with a rear engine turbo lump .
I would imagine that the alloy upright will expand alot more than the bearing and would expect the brg too become loose -er in its fit ,not tighter if anything as the steel brg will not expand as much as the upright ,which is why you make it an interference fit to start with
as i see it in your design doesnot have a factory made preload spacer.
So your single bolt +its torque setting is what will be very critical to the preload it gets when at running temp ,then add the expansion of the hub to complicate things
--where as with a preloaded single cased double row brg ,the preload variable is not there to the same extent as all the components are of basically same material in the brg .

very interesting anyway

and I am not attmpting to make derogaotry comments on your design --not in anyway --just different ways of looking at things

8th April 2013, 16:30

Yes the majority of heat goes through the brakes, into the brake flange and then from there the route to the upright is through the rest of the hub, then the bearings, then the upright. I believe that this route will conduct more heat to the upright than radiant heat going straight to the upright from the disc. And as long as the outside of the upright remains cooler than the centre, the centre should expand fairly uniformly and not tend outwards away from the bearing.
I hat the number of variables in this design process lol.
In regards to preload:
The preload of the pair of bearings will be applied until the inner races compress against the preload spacer. At this point any more pressure will preload the bolt and not the bearing set. This preload of the bolt will then be affected in expansion, eventually getting to a point where the bearings will leave the face of the preload spacer. Which i hope wont happen.

8th April 2013, 23:21

Better view of the conical spline hub face. And i've done the FEA on it today and it's done pretty well i must say. Nothing exploded so success.

2nd May 2013, 16:48

Final rendering of the full assembly. Now just to finish the write up -_-

5th May 2013, 19:33

Awesome.

How many hours did that take on Solidworks?

5th May 2013, 19:48

Several......lol. i didn't really keep track, as it was done alongside lots of other work and along the research needed for each element of the design. But i reckon (with the upright done last year) around 15 hours, maybe 20 with the FEA. Hard to say as its not like you are doing it non stop drawing a cad model of an engineering drawing fort example. You think you draw, you assess, you edit, you draw more, you assess, you research, you delete, you re draw, etc etc.

6th May 2013, 00:08

Looks really good matey, got all my dissertation stuff finished and handed in now cant wait to finish!

16th May 2013, 13:35

3D prototype is complete!
Pretty cool to have it in my hands. Smaller than i imagined it lol, despite the numerous scale drawings i have.

16th May 2013, 15:04

Also, something that is apparently often forgotten about in design offices, tools. Your design may be perfect, but if you cant get the tools to the fixings then what's the point.

"like a glove"

16th May 2013, 15:14

Looks good matey, i had the rod and piston made up from my diss it makes it much more worthwhile actually having it in your hand dosent it!

16th May 2013, 15:16

Yeah it is quite odd after so long being in front of you in the computer. I kept trying to click the section view button, but i don't have one on my desk lol

16th May 2013, 15:21

Hahaha!

17th May 2013, 07:18

we do this line of work at my company, just bought an object 3d printer!

17th May 2013, 12:50

The process i am keeping my eye on is laser set metal alm. So the same thing as this but with laser melted metal powder. A few German companies are starting it up, super expensive mind you. All the current metal alm is glue together and then covered in sand, then melted. Like a strange pre casting technique.

17th May 2013, 23:14

Might be a stupid question. But is the the stuff that gets printed into a resin? then sets to build up layer by layer?

I only ask because Honda Moto GP are running actual race parts made from the stuff at the mo such as cam covers and aux covers. Not sure if its the actual stuff you use or a variant but it makes sense to use this rather than carry all the separate parts when you can just "print them".

Also i bet it feels amazing to see something in real life touchable form that you have been working for so long on.

18th May 2013, 00:38

This is a sort of polymer plaster that is lightly sprayed with a binding agent layer by layer. Once removed from the printer it is still fragile and then infiltrated with glue. The type this is made of i don't think is all that strong, so to actually make functional parts you would probably just change the glue used.

18th May 2013, 01:19

Yea that stuff is fragile, I had a little hub cap made at 3mm WT and I snapped it by pressing abit to hard when putting it in an alloy wheel.

I was suprised how heavy it is too, my piston weighs more than double what the real one would.

18th May 2013, 01:25

expensive mistake lol.
Mine aren't too heavy. lighter than aluminium

18th May 2013, 01:28

Really? Mines stupidly heavy for what it is like.

Lol I know I was gutted, good job I didnt have to pay for it!

18th May 2013, 01:31

That was with cheap kitchen scales, so results may vary haha

20th August 2013, 20:43

Bored over the summer, So finished the brake bell and disc assembly

5th September 2013, 01:36

Brake caliper done. Ap Racing CP4227-2S0
Just got to do all the hardware and the bracket.

5th September 2013, 01:36