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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Speet Brake Installation Query
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<blockquote data-quote="Gary Gittleson" data-source="post: 110575" data-attributes="member: 3625"><p>Well, here's my take.</p><p></p><p>Imagine that instead of a brake at the end of each cable, we have a spring with say 40 lbs/inch Hooke's constant. In that case, if we pull one cable (without the balance beam) 1/4", we experience a 10 lb force. If we use a Vincent Speet setup and pull both brakes together the same 1/4", we will have two springs applying 10 lbs resistance each for a total of 20 lbs.</p><p></p><p>It's easy to see that the balance beam will halve that force. The 1/4" movement at the "primary" end of the balance beam will be split in two, pulling that spring 1/8" and the other the same 1/8" via the 1/8" movement of the beam, thus causing a 5 lb resistance at each spring for a total of 10 lbs. So to get the same 20 lbs, we will have to move the cable 1/2".</p><p></p><p>That's a 2:1 mechanical advantage. But the levers of the actual Speet brakes were designed so as to apply proper braking with reasonable handle movement in a 1:1 setup. Using the balance beam with no other modifications would have us pulling the handle back to the bar before we have full braking. So one has to figure out how to hook up cables from the balance beam to the Speet brakes, which in standard form require a near-horizontal cable approach and to reduce the mechanical advantage. I just spoke to my friend (Tom Newman) and he reminded me that there's an article of his work on a fairly recent MPH. I'm going to try to find the issue. There's more to be said about this. I'm either going to get him signed up on the forum or act as liaison. More info to come.</p><p></p><p>Gary</p></blockquote><p></p>
[QUOTE="Gary Gittleson, post: 110575, member: 3625"] Well, here's my take. Imagine that instead of a brake at the end of each cable, we have a spring with say 40 lbs/inch Hooke's constant. In that case, if we pull one cable (without the balance beam) 1/4", we experience a 10 lb force. If we use a Vincent Speet setup and pull both brakes together the same 1/4", we will have two springs applying 10 lbs resistance each for a total of 20 lbs. It's easy to see that the balance beam will halve that force. The 1/4" movement at the "primary" end of the balance beam will be split in two, pulling that spring 1/8" and the other the same 1/8" via the 1/8" movement of the beam, thus causing a 5 lb resistance at each spring for a total of 10 lbs. So to get the same 20 lbs, we will have to move the cable 1/2". That's a 2:1 mechanical advantage. But the levers of the actual Speet brakes were designed so as to apply proper braking with reasonable handle movement in a 1:1 setup. Using the balance beam with no other modifications would have us pulling the handle back to the bar before we have full braking. So one has to figure out how to hook up cables from the balance beam to the Speet brakes, which in standard form require a near-horizontal cable approach and to reduce the mechanical advantage. I just spoke to my friend (Tom Newman) and he reminded me that there's an article of his work on a fairly recent MPH. I'm going to try to find the issue. There's more to be said about this. I'm either going to get him signed up on the forum or act as liaison. More info to come. Gary [/QUOTE]
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Tech. Advice: Series 'B' / 'C' 500cc/1000cc Bikes
Speet Brake Installation Query
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