PDA

View Full Version : Glue type question



wierdscience
03-08-2004, 11:31 PM
I got a disc brake/fan blade off my big Dewalt radial arm saw,it is an aluminum blade with a steel brake surface bonded on,well after 20 years the lining is seperating and I need to glue it back on any idea of what glue to use?

winchman
03-09-2004, 12:07 AM
I sure would like to see a photo of the brake parts you're working on. I'm interested in magnetic brakes for a possible application on my winches.

As for an adhesive, I'd suggest instant glue. Just get the little tubes in the bubble packs from Home Depot. They're hard to beat for a quick fix on clean surfaces.

Roger

ACF
03-09-2004, 12:47 AM
Being this is a brake and will see some heat, I'd try a 2 part epoxy.

Chris

jfsmith
03-09-2004, 12:51 AM
I would use Devcon 2 Ton Epxoy for such a thing. Abrade the surfaces or bead blast them to open the pores up, don't clamp too tightly, let stand for 24 hours and you should be fine.

Jerry

x39
03-09-2004, 01:16 AM
My personal favorite: Loc-Tite "Black Max".

docsteve66
03-09-2004, 12:34 PM
Glue for brakes?
I once burned up a set of brakes on a Chrysler, coming down Mt Wilson (about 1951). Burned em to a crisp, and NO rivets left. Parts place sold me a replacement set- NO RIVITS!!!! Glued on. So what kind of glue did the job? Brake man explained to me that the glue only held the linings in place. He said the friction on both side of the brakes did the job and that since static friction force ALWAYS exceeded that of dynamic (sliding), there was no danger of the brake pads slipping, so the glue only had to be good 'nuff to keep the pads (or shoes) in place. So any glue would do. Pretty clever!!!

I,ve saved used the static/dynamic friction thing several times when in trouble. So for saw I would not worry to much, use a LITTLE bit of glue or a rivet or groove and try to have contact area on the static side larger than that on the sliding side (and on drum brakes it usually is.

BTW, I notice that pads are riveted again (at least on some cars). Does that mean the laws of physics have changed, or the original theory was flawed or (most likely) that the regulations some where call for rivets so that what we get? So maybe you best not follow my advice or reasoning http://bbs.homeshopmachinist.net//smile.gif

debequem
03-09-2004, 01:53 PM
Hmm, any glue will do?

Just a thought, but what if the heat from the brake pad was hot enough to melt the glue? If the glue were to melt, then wouldn't the bond between the metal shoe and the pad be reduced to the viscosity of the liquified glue?

My thought would be that it might be possible for the glue's viscosity to create a static friction coefficient that is lower than the dynamic friction between pad and rotor. In other words, the glue becomes a lubricant and the pad debonds.

What do you think?

Marv

Mike W
03-09-2004, 02:38 PM
How about JB Weld? My favorite glue for general use is Goop. As long as there is enough surface area, I trust it more then epoxy.

glenj
03-09-2004, 03:18 PM
I second the Black Max. I have a bicycle suspension fork with AerMet 100(300,000psi steel alloy) blades bonded into a 6061-T6 crown and they have not budged in 4 years of abuse.

nitacboss
03-09-2004, 08:05 PM
Be careful, I have heard, but not checked out myself, that dried Black Max is electrically conductive due to the amount of carbon in it. Might be worth looking into. Right now all I have is Permabond 910 (Eastman 910?) so I couldn't lay a bead and check it with a meter.

docsteve66
03-09-2004, 09:26 PM
When I said "Little" I meant small spots. Marv has it right,I think. If the pads were covered with glue, you would depend on the glue's shear strength plus what ever the friction is between the glue and the pad and the backing. I prefer rivets-simple reliable and the rivets, like the glue just hold the pads in place.

We have some men here in the race car business- how do the modern racers hold the pads? I quit the performance car stuff when Oldsmobile made the 180 HP engine on stock cars and we were working hard to get same HP with flat head ford blocks converted to overhead valve (50 years ago). All asked of binders was that that stop and not pull right or left. European sports cars changed all that too- suspension and handling gave thrills that dragging did not.

What ever works for a car should stop a saw.

wierdscience
03-10-2004, 12:24 AM
Okay,I took the two pieces of the rotor/cooling fan and seperated what remained of the glue,sandblasted to white both sides,made up a little jig with a wingnut and washer to clamp the thing flat,coated the two halves with octite t-primer and troweled on a thin coat of JB WELD(its what I had),its dry now and I'll try it out tommorow.

Winchman,this brake is noting more than an auto a/c clutch magnet used in reverse,the moveable disc is held against the brake disc/fan on the end of the motor shaft by a spring steel wave washer,when you turn the saw on a brake release circut sends 90vdc to the brake coil and sucks the moveable disc against the magnet coil releasing the brake,when you kill power to the saw the spring washer pushes the movable disc against the disc/fan blade and stops the saw.I'll take some pics and post them tommorow.

Paul Gauthier
03-10-2004, 02:05 PM
Acra-Glas from Brownells.

------------------
Paul G.

Thrud
03-11-2004, 05:21 AM
Black Max will break down at about 250*F

JB weld has better thermal conductivity, can be machined, is much stronger structurally, and does not break down into cyanide components as does instant glues.