Sunday, February 14, 2010

making a p-clamp

dont ask me why, but i felt the need to make some serious p-clamps. these are a bit different than your standard p-clamp.

they use an m4 and m5 bolt. the m4 holds the clamp to the fork leg, and the m5 bolts the rack to the clamp.
doing it this way has a couple nice features. as you tighten a single bolt p-clamp it wants to move, pulling the rack out of place as the p-clamp tabs pull together. the m4 bolt holds the clamp firmly in place so when you tighten the rack bolt it doesnt pull in as it would with single-bolt p-clamp. also you can remove the rack and leave the p-clamp on the bike, already in the proper position to quickly re-install the rack.

this set is made out of 4130, its what i had on hand. its gonna rust if left uncoated. im thinking about re-doing it all out of stainless when i get more metal stock.

its hard to tell in this picture, but there are 7-layers to this clamp.

outer plate
p-clamp tab
cloth bar tape
inner plate
cloth bar tape
p-clamp tab
outer plate

a very solid connection
and of course i spent a couple minutes on the lathe to machine the aluminum spacer!


Anonymous said...

Dannnnn... thou art the maaaan.. you improved the P-clamp... Hayzuess Krispies... this can stay on bikes all winter long to hold fenders and such...

one thought -- use old Conti (er, any kind) of tires cut to take the place of cloth tape...?

ditto... maybe just chainring washers or presta valve nuts to space the ears apart?
though that machined spacer is cooler...

Please give us a price per hundred (er, dozen?) and also patent it... asap...
it's a basic invention!
like the dang pyramids...
yes as a matter of fact today is my day off...
in other news"
phila mar 20, memorial hall,uk/busc

chance of having a front rack to show is low I realize
chance of lending you a Brompton for the day is v ery high regardless..

D n L said...

hey mike,
i used the cloth for a couple reasons... it slides on the fork leg, so the clamp can align itself as you tighten the bolts. rubber would make it very difficult to get the tabs square to the rack mount.
i experimented with rubber, but it was too dang hard to punch holes it it! i used a soldering iron to burn holes through the cloth. also the adhesive on the cloth is quite convenient for sticking to to the clamp.