brake caliper mounting

[URracing]

We are using a 1/4" thick mild steel plate that we plan on using to attach our brake caliper with. Each plate will be bolted to a machined aluminum upright. We are using Wilwood Dynalite Single Piston Floating Calipers on each corner. I'm just curious to see what we have to do in order to lock the threads on the floating pins from turning out of the steel plate. Do we use loctite on these threads? Or anything at all? I'm not too sure exactly how much heat is going to be radiated through the caliper to these pins but to me loctite may not be the ideal solution because of this.

Just curious to see what other teams use on this application.

TIA,

Brett

[Faterooski]

Loctite will definately weaken at higher temperatures...whether your brake calipers reach this "higher temperature" is up to you to determine I guess. Someone on here can probably point you towards finding out a strength vs. temp relation for Loctite. Loctite's High-Temp formula would be a better option. A nylock or a interference locknut would be a much better option than either flavor of Loctite. As good as Loctite is (we used to call 609 the "Hand-of-God" formula), a positive locking device (Nylock, interference nut, cotter pin, castle nut, safety wire, etc.) will is a much better choice for keeping racecar fasteners where they are supposed to be.
And yes, use a locking device....I used to think they would never come into play until a cotter pin held on our left rear wheel at an autocross. The rules committee mandates them for a reason.

[kwancho]

For what it's worth, the nylon's good to about 250F. Forum searching tells me that uprights only get to about 150-200F. Does anyone have problems using nylon locknuts to attach, say, upper and lower ball joints?

[Alan]

If you are looking at what kind of hardware to use, I would recommend Aircraft Spruce or Coast Fabrication.

http://www.aircraftspruce.com/catalog/hapages/an363.php

MS21042s will probably suit your application if I'm reading it right. I wouldn't use a Nylock or Loctite when a good nut and bolt should do the trick. If you are still unsure of the integrity of the connection, safety wire should help.

[kwancho]

Nice. The AN363 look like expanding type. Are the MS21042's distorted thread?

[HenningO]

While on the subject, Formula Student Germany rules, specifically ban nyloc to secure any component of the brake system.

[Biggy72]

How much room do you have designed between the rotor and the brake caliper mount? I know for ours there's not much room. We ended up just safety wiring everything together and we had a heck of a time getting two threads to show. Now looking back it would have been nice to find a radial mount caliper and then just safety wire the heads, but I haven't found any cheap radial mount calipers either so....

[URracing]

The caliper comes with its own floating pins which have 7/16" x 14 threads. The threads are about 3/8" long so to me that means they are meant to be threaded into a 3/8" thick plate. I'm just trying to figure out if there is any way to keep those pins tight.

Safety wire wouldn't be too ideal since I believe it still allows the pins to loosen but not come right out. If those pins loosen even a little bit, it throws out the alignment of the caliper to the mounting tab and results in brake failure since the pad/caliper wouldn't be able to float freely.

A locking nut would be better except we don't have enough thread to work with for this application. I do agree though, the heat may play around with the loctite a little, possibly even allowing the compound to drip onto the rotor if it gets hot enough, which isn't good.

Once the caliper is mounted, the distance between the mounted surface and the rotor is VERY minimal so we don't have alot of room to play around with in that regards.

Any other ideas would be greatly appreciated.

Question: Would 6061-T6 aluminum be okay for the brake tab? I noticed a few teams machine a brake mount right on their uprights but I'm just curious if the heat generated by the brakes will compromise the integrity of the tab. Right now we are looking to make the tab from either 1/4" mild steel plate or angle iron, but still researching some ideas since we do not have 6-axis laser or hydrojet cutting available in our area which would be required to do the cuts if we make the tab out of angle iron. If we do, our only other alternative would be to throw it under a mill.

Ideas appreciated.

[BeaverGuy]

Nobody has mentioned that Loctite is not considered an acceptable means of positive retention. The rules regarding retaining fasteners is as follows.

"3.7.2.2 Securing Fasteners
All critical bolt, nuts, and other fasteners on the steering, braking, driver's harness,
and suspension must be secured from unintentional loosening by the use of positive
locking mechanisms. Positive locking mechanisms include:
- Correctly installed safety wiring
- Cotter pins
- Nylon lock nuts
- Prevailing torque lock nuts
Note: Lock washers and thread locking compounds, e.g. Loctite®, DO NOT meet
the positive locking requirement.
There must be a minimum of two (2) full threads projecting from any lock nut.
All spherical rod ends and spherical bearings on the steering or suspension must be
in double shear or captured by having a screw/bolt head or washer with an O.D. that
is larger than spherical bearing housing I.D.
Adjustable tie-rod ends must be constrained with a jam nut to prevent loosening."

[Alastair Clarke]

We've used investment cast uprights for a number of years which have an integral caliper mount. The material is a casting alloy which is quite similar to 6061, and we've had no problems as regards loss of strength etc on the caliper mount. The items get regularly crack-checked etc so I would hope we'd have picked up any problems.

[URracing]

In regards to the actual caliper mounts, we have decided to go with 1/4" thick angle iron. We have to get the cutouts milled out since we do not have a 6-axis laser table that is capable of getting the head in close enough to the angle.

Two questions remaining in regards to fasteners.

We are running a Wilwood Dynalite Single Floater caliper. The half inch floating pins are threaded into the caliper mounting tabs and after talking with Wilwood, they claim these floating pins should not become loose.

My question is, do we have to install a positive locking device on these pins? We can't really do anything on the threads since they are only 3/8" long and therefore need to be fully threaded into a 3/8" thick plate to be installed properly.

I was thinking our only option is welding some kind of safey wire to the head of the pin and attaching it to the caliper somewhere.

My next question is...

The rules state that at least two threads need to be shown with any lock nut.

Our Kodiak wheels use 18 stover lock nuts around the outside to hold the centers in. None of these have even one full thread showing. The end of the bolt is flush with the top of the nut. Does this mean we have to replace 72 little bolts with longer ones?

[Drew Price]

My question is, do we have to install a positive locking device on these pins?

Does this mean we have to replace 72 little bolts with longer ones?

My interpretation says that the answer to both of these questions is "Yes".

For your calipers maybe that means that you will have to make different fasteners, or figure out a way to use a cotter pin or safety wire? Hopefully there is space somewhere...

Best,
Drew

[Derf]

There's a little clarification in the official forum's FAQ (http://www.formulasae.org/forums/formula/dispatch.cgi/rules/docProfile/100177/d20071016191850/No/3.7.2.2%20Wheel%20Nuts) pertaining to wheels.

[Marshall Grice]

Does this mean we have to replace 72 little bolts with longer ones?

No, you don't have to replace 72 bolts. The rules say "critical" fasteners. Any one (or more) of the bolts could fail and not cause a failure of the system, therefore are not critical.

if one brake bolt falls out or one ball joint bolt falls out, you have a serious problem on your hands.

[Drew Price]

Marshall,

I had been interpreting that as 'fasteners for critical components' and playing it on the safe side, so it was interesting to note that 'critical' is implied to mean systems with only one or two fasteners.

Thanks Derf, I remember reading that a while back, but forgot about it for some reason.

Best,
Drew