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Identifying brake calipers

Flow

Member
Hello folks,

Can any one help me identify my calipers? They looks like they might be from a motorcycle rear disc with that banjo fitting, R7 hose, a cast alloy finish and the bleed nipple on the top? I am re-working the system with PTFE / SS flex and EPDM seals. I have the master cylinders sorted but struggling to place the calipers.

Apologies this is the best photo I have of it as the hangar is a 7hr drive away and am currently locked out of visiting it due to the virus so I can't pull it off and check the pad form factor, part numbers or pull the piston etc.

If anyone can positively ID it, I can order parts now to save waiting for them during the next precious break in lockdown where I will get to work on it again.

Brake Calipers.jpg
 
Probably so. The hose---or at least the outside cover is 30R7-- that is NOT for brakes, especially DOT3. The caliper seals, if a motorcycle or other vehicle would have seals compatible with DOT3, not aviation Mil fluid.

I dont see a crimp collar around the hose, so I suspect the 'hose' is just a cover for an underlying hose. Hope so.

What plane is this on?

Tom
 
Gosh Colin, I really think you have cracked it. Seems to be a casting used on a number of ATVs etc.. How on earth did you manage to pick that!?
 
Jason---the bigger question is what plane are you using this on?

Tom

+1

I would be concerned that an ATV brake caliper would either provide inadequate stopping power or risk significant overheating for a 1700# airplane. It may be able to stop the plane, but may produce twice as much heat in the process, due to a limited surface area contact between pad and rotor.
 
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Gosh Colin, I really think you have cracked it. Seems to be a casting used on a number of ATVs etc.. How on earth did you manage to pick that!?

I used to restore/rebuild old motorcycles and ATVs, so my google-foo is strong.
 
Well done! :) Conservatively this is a ~55,000 ft.lbs or 75 KJ per wheel aircraft. The disc is steel, 3.6 mm thick, 220 mm OD with a swept area mass of ~570 g new and 475 g at 3 mm thick. The pads have a max temp rating of 450 C continuous and 700 C intermittent. Matco uses 700 f as their benchmark which is nice conservative number.

If we use a conservative 75 KJ per wheel using speeds above part 25 requirements for RTO calculations, a conservative 700 f for the delta along with the min wear thickness of the disk at 3 mm and account for no 2nd or 3rd order effects nor any heat dissipation into the rest of the rotor or pads/caliper we need 86 KJ to heat the friction disk up 700 f so a tidy fudge factor on top of the existing. With a new limits disk and using an 800 f delta (just before the steel glow temp) we are at 118 KJ per wheel.

This looks like the pads at ~1.9 sq in or slightly more than the TL-2000 Sting and about the same as the Dynamic WT9, Eurostar, Harmony LSA aircraft or ~5% less area than the Tecnam 2002 but that is an 80,000 ft.lbs per wheel aircraft in certified form:
Pads.PNG

This looks like the rebuild kit which will have EPDM seals:
Rebuild kit.PNG

To add to the picture the wheels are 8"x3" and tires are 400x8.
I see that some CRF 150 riders say they can bolt on CRF 450 twin pot calipers so that could be an easy upgrade option if more torque is required at 450 psi.
It looks like the pads come in a range of friction coefficients including temperature stable graphs suitable for rear brakes (and aircraft) in the 0.5 to 0.45 μ range and some contamination stable low μ graphs for dirt bikes to provide consistent modulation on loose and wet surfaces. My bet is that it has these it in at the moment which is why they feel predictable on the grass but ultimately soft.

For reference light aircraft compounds are typically speced to ~0.45 μ

Would I prefer magnesium wheels and inside calipers for tight wheel pants? Certainly, however this looks to have been quite a smart budget set up so far.
 
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