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Manufacturing Brake Rotors

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Akash View Drop Down
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    Posted: Nov/23/2012 at 5:36am
We have decided to manufacture our own brake rotors this season. After a lot of research and discussions with the professors I have decided to go with stainless steel 420. The plate we are receiving is 6mm thick. We will firstly surface grind it to 4mm, then water jet cut the profile and the Bolt Circle Diameter, and then get it chrome plated. Since its the first time we are attempting it I am slightly skeptical about the whole thing. Any suggestions are welcome.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick914 Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 8:16am
Very important criteria: compatibility of the pads with the rotor material.
Last time we used stainless discs, we ran through the disc and a set of pads within a competition.
Now running low carbon steel discs and the wear is barely mesurable.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rohitkj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 2:10pm
The pads are sintered metallic, and sintered metallic brake pads are supposed to work well with steel rotors.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Purduebaja Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 4:58pm
Is there a reason you want to use 420 Stainless? We currently buy rotors but are looking to make custom ones this year. What I have seen on the Baja and Formula forums is that most teams use cast iron or 1018 mild steel. One of the advantages of cast iron I have seen is that it can handle a higher heat input and loads. This makes sense to me in Formula as they are regularly braking from high speeds to very low speeds and may have issues with heat management.

As far as baja goes though how often do we really use our brakes? And if we do its usually with a ~300-500 lb vehicle from ~25-35 mph to some lower speed. We personally will be going with cheap, easy to obtain and easy to work with 1018 steel as I have heard many success stories. I feel that anything above this is overkill, at least in Baja SAE.

Also why wouldn't you surface grind after waterjet. Im no expert on water jet cutting but I feel that I would create some burrs that you would want to be flat before mounting them on the car? Surface grinding 2mm of material also sounds like it would take a long time. You may want to consider getting closer to 4mm with some other process before going to surface grinding. Lastly, what is the point of the chrome plating? Guess I've never seen a chrome, or stainless rotor before.

That's just my $0.02. However I do feel some other people on here will disagree with me.

Edited by Purduebaja - Nov/23/2012 at 5:05pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DomUL Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 6:27pm
I would say that braking can involve some heat depending a lot on the track. From my experience yes I used brakes... way more than I thought. For example, on the 2011 Illinois track I had at least 4-5 big braking spot/lap (from high speed to on the edge of blocking the wheels) and many other less intense. Surely not as intense as formula but still noticeably.
 
 
Since in baja you can have a hard braking dirctly followed by a water pond (quenching) carbon content is important to consider. But since you need less braking power than formula cars, you'll probably need a smaller (diameter/thickness/cutouts/whatever) rotor so it may heat up quicker (cool down quicker too though).
 
 
That being said, rotor material/shape should be determined with heat and strength in mind according to your needs but as purduebaja said, you'll probably don't need very expensive material. Be sure of you brake pads compatibility too, was quite an issue for us in the past.

Edited by DomUL - Nov/23/2012 at 6:30pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AndyRIT Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 8:41pm
When I was on the team we used aluminum rotors with a hard coating (I have no idea what coating) with matching pad material, at one point. This set-up worked well until the coating wore off the rotors. Not sure what they are using now.
Your best bet is to find a shop/supplier that has knowledge of brake pad/clutch materials. It is very important to match the pad material to the rotor material.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote otto Quote  Post ReplyReply Direct Link To This Post Posted: Nov/23/2012 at 10:59pm
for reference, mtb brakes are stainless and are generally matched with sintered metallic pads.  You can also get some sort of organic material pads, but those are terrible.  That being said, who knows what goes into brand specific sintered metallic pads, I'd bet everyone has a slightly different formula.  Downhill bikes can make extensive use of the brakes (depending on the course/trail/terrain) and they see lots of heat... there's a reason fork manufacturers put the damper in the right leg and the brakes on the left leg - so I wouldn't discount taking design tips from them just based on the fact that they're for bicycles and not ATVs.  Most of the stuff you see on ATVs is cost/durability oriented rather than performance/weight so you see a lot of solid, mild steel rotors out there with maybe some choice cross drilling.

sooooo stainless should be fine, but the question is which type of stainless.  there may also be issues with laser cutting vs. waterjet or milling with localized hardening etc (I would give preference to water jet or milling the rotors). 420, 440 and 17-PH all look to be decent choices.

on the cornell baja cars we used to use 4130 plate (mainly because we had it on hand, decent yield strength) and had it waterjet by a sponsor or milled with a knee mill than had a controller retrofit.  used sintered pads with those rotors.  Looking back, stainless would be the logical redesign material of choice just to keep them from rusting all the time.  Cutout geometry primarily controls rotor/pad wear.  Heat dissipation has been hinted as being a relatively small issue and I doubt you'll ever notice any brake fade due to excessive heat at baja races.

riveting on an aluminum center would be a nice touch, helps dissipate heat more and lets the rotor expand slightly less constrained radially as it heats up. Plus it saves weight.  I think Miami of Ohio had bare aluminum rotors in auburn 2012 and struggled to pass brake tech.... imagine your pads full of mushy aluminum, no good.

hope tech, avid, and formula all make nice rotors and calipers for the bicycle market
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rohitkj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/24/2012 at 12:39am
Water jet cutting gives a near perfect cut (i.e if you go for the very thin cutting water jet,Q5), no burrs, whereas laser cutting creates a heat affected zone,  As for the surface grinding , we are doing it first since the material might have surface imperfections when it reaches us.
And 4mm thick cast iorn rotors would just be to brittle. stainless steel 420 has good hardness,corrosion resistance.
And stainless steel rotors work perfectly with sintered metallic pads.
Chrome Pating gives it extra hardness, wear resistence, so your pads are not going to dig into your rotors.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote APhillips Quote  Post ReplyReply Direct Link To This Post Posted: Nov/28/2012 at 4:19pm
Rohitkj,

There is generally two types of chrome plating - decorative chrome and hard chrome. Decorative chrome is what you see on bumpers and only serves as decoration (and a bit of corrosion resistance.) Hard chrome will give you extra hardness (not that you need it,) and better corrosion resistance (not that you need it.) However, to function like this hard chrome is generally applied much thicker, around .1mm minimum per side - so the thickness of your rotor would increase at least .2mm. Because of this increase, parts are generally made undersize, allowed to be coated oversize, and ground back down to size. This further allows for a better surface finish to help reduce wear, since you were apparently concerned enough with wear to hard chrome it in the first place. 

Anyway, my point is that to do hard chrome correctly, you'd have to grind down your stock, waterjet the pattern, chrome them, and grind them again. And at the end of the day, the whole point of stainless is that it already has the properties you desire from the chrome, so is it really worth the additional manufacturing processes?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote rohitkj Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2012 at 1:20am
Stainless Steel 420 is turning out to be very tough to get, I might just go with SS410. It's almost the same, just the SS420 is a bit harder.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote otto Quote  Post ReplyReply Direct Link To This Post Posted: Nov/30/2012 at 4:59am
Originally posted by rohitkj rohitkj wrote:

Stainless Steel 420 is turning out to be very tough to get, I might just go with SS410. It's almost the same, just the SS420 is a bit harder.


I would look into 17-4 PH if you can find it - best strength (about 760MPa yield) and hardness (about 40 rockwell-C) of the group

Edited by otto - Nov/30/2012 at 5:02am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Graeter Quote  Post ReplyReply Direct Link To This Post Posted: Dec/08/2012 at 1:30pm
Originally posted by otto otto wrote:

I think Miami of Ohio had bare aluminum rotors in auburn 2012 and struggled to pass brake tech.... imagine your pads full of mushy aluminum, no good.
Yea, we had tried a set of hardcoat anodized aluminum rotors. Worked well in testing, but damn near instantly when the coating wore off, the aluminum bedded horribly into the pads. When that happened we even had issues with using steel rotors to stop the car.

On that note, for Wisconsin we changed pads and rotors to steel and a high friction pad and we passed first try there without even really trying at all. 
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First of all, I appreciate you because you are doing a good work. I am new in this field, so I have not much experience. I just started it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote akash khamkar Quote  Post ReplyReply Direct Link To This Post Posted: Oct/07/2017 at 8:53am
For first time you can use any material with high strength  , but what you actually need is hardness . Firstly decide which brake pads you are going to use . According to that , keep hardness of your disc more than that of brake pads . Most of the time , it is easy and economical change brake pads than changing brake disc .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sujandinesh Quote  Post ReplyReply Direct Link To This Post Posted: Oct/07/2017 at 4:31pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ritwik_101 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/21/2017 at 3:23am
We are also thinking of using 1018 steel for disk brake of 3 mm . Will it be a good idea to proceed ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sujandinesh Quote  Post ReplyReply Direct Link To This Post Posted: Oct/22/2017 at 9:39am
Before directly asking for a solution here, rather state why you would choose/not choose the material. 

Brake discs can be manufactured with plenty of materials, especially for a BAJA car, so stating your reasoning behind the material choice would help you take the right decision. 
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The issue is that the heat flux from our calculations are coming out to be in order of 100k . On analysing, we find the temperature to be in the range of 800-1000 K. This was for MS. The temperature drops to 700 for GCI. We want to make sure on two things :

1. Calculations
2. Film coeffecient.

Also, what is the film coeffecient of GCI, MS and AISI 1018 ?

Thanks in advance !!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sujandinesh Quote  Post ReplyReply Direct Link To This Post Posted: Oct/23/2017 at 2:20pm
The temperatures you have mentioned are a bit too high and I am unsure about your method of calculation. 

Could you briefly describe your process?

Also, why would you require the film co-efficients? 

Finally, the best thing in any design calculation is to close the loop. So, if you have your previous BAJA car and an infrared gun, you could validate your results yourself! 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Vishalpatel1975 Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2018 at 12:10am
Hello..we also had planned to used SS brake disc at time but at the time of surface grinding we were unable to find any one who us to work on SS grinding. Because only MS or other metals were b grinding due to there material magnetic properties. Whereas in SS didn't have magnetic properties so the can't clam it on magnetic bed. So can you please help me out that how did you get that SS fisc surface grind. That process of clamping the SS discs ? The type of machine they used ? Any photos of it ?
Please it would b great if you could help with this problem.
Thank you.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote RLM Quote  Post ReplyReply Direct Link To This Post Posted: Feb/27/2018 at 7:55am
some grades of stainless steel are magnetic. a lot of motorcycle rotors are made from 4xx series stainless which is magnetic and can therefore be surface ground. if your using something like 316 SS lasercut from sheet, the surface finish will be fine for this application as long as the sheet itsefl was very flat and not warped.
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