From: bleep@ux1.cso.uiuc.edu Date: Fri, 26 Mar 93 15:01:23 CST Subject: post to hpv:trike braking question Hi. I post the orginal question about just using front brake on my trike design. I was warned that this this might cause me to flip over. As I understand about the dynamics of braking, at least that which is applicable to uprights, most of the braking force comes from the front wheel. Little of this braking force comes from the rear wheel, which locks up as soon as the cm shifts sufficiently forward to lift the rear. Now, this to me seems to indicate that a face plant would be caused by a threshold deceleration value, regardless whether or not a rear brake is applied. I was taught to use the rear brake as an warning device for face planting: as soon as I feel the rear locking up, I ease off the levers. Is this correct procedure? To slow down (non-emergencies), I often just use my front brake, which has a much stronger effect than the rear one--I never been flipped doing this (may be I'm lucky). Can a knowledgeable person elaborate on the function of the rear brake? As I asked before, can you also do this with some scientific-engineering references/details? Much thanks for all your time Tho Bui. P.S.: what do you guys think of that bike-car in Bicycling magazine this month? 100 lbs. seems like a lot of weight. From: damouth@wrc.xerox.com (David E. Damouth) Date: Mon, 29 Mar 1993 06:53:36 PST Subject: Re: trike braking question Right observation - but I think you are drawing the wrong conclusions as they apply to your trike design. The general principle is that the wheel with the most weight on it does the most braking (assuming you are not limited by badly designed brakes.) The maximum braking force is directly proportional to the total downward force on the wheel. On an upright, there's another confusion factor, in that rear brake cables tend to be long and spongy. The reason your rear wheel locks up and doesn't brake much in an upright bike is that during hard braking most of the downward force is on the front wheel. Your trike-truck design (when carrying a load) has a much greater fraction of the total weight on the back wheels, and this weight is (I presume) also mounted quite low, minimizing the dynamic weight transfer to the front during braking. So it's likely to be the front wheel which locks up prematurely, providing very little stopping power. This is why several of us strongly suggested that you won't be able to stop quickly without rear brakes. /Dave From: Matthew Kleinmann Date: Mon, 29 Mar 1993 10:57:23 -0500 Subject: Re: trike braking question I see what you mean. I have been re thinking the rear end of the trike quite a bit. I like the idea of using the ratchets in the free wheels to allow the rear tired to move independently, and I have been thinking about building some kind of a disk brake into the rear axel assembly. I need to get a pair of rear wheels and figure out how to use the ratchet assemblies in them. Building an axel for ball bearings is pretty easy but I am not sure how to get the gear cluster attached to the axel and still have the wheel spin free. --Matthew From: mason@asylum.sf.ca.us (Latte' Jed) Date: Mon, 29 Mar 93 21:07:13 -0500 (EST) Subject: Re: trike braking question For attaching a freewheel to an axle, I'll assume the axle will be somewhere around 1" steel tube, preferably chromoly. You could make a fat part of the axle and just thread the freewheel onto it. This is even easier than it seems because a freewheel will thread onto a bottom bracket cup - I think it's the lock-ring side of a japanese (english?) BB. So you can jam it on with the lockring, or just braze the lock ring on and torque the freewheel against it. Machine out the cup to fit snugly over the axle and weld or braze it in place.