Saturday, February 15, 2014
It's A Question Of Proportion
Since I can't afford the motor I want for Frankenbike, yet, I have been spending the past couple of days trying to work out a few of the other details I want her to have. One of the things I have been wanting to do, but couldnt quite get my head around was just using the foot brake to run both front and rear brakes. Then, just by chance I was reading an old article in a copy of Hints & Kinks about that very thing. Using a proportioning valve to keep the pressures even. For a stripped down Sporty, that was just what I was looking for.
So I did a little bit of research, and found a wide array of thought on the matter. Why some people would want to do it on a bagger, or a big heavy bike with abs, and other crap is beyond me. All I wanted was to keep the bike looking as clean as possible, and to stop as smoothly as I can make it.
With no front brake master cylinder and lever on the bars, that would give her a real clean look. Since the bike will be set up to ride solo only, I figure I wont need to worry about an adjustible proportioning valve. So what I have been thinking about doing is running the rear brake master cylinder to the valve, and both lines from there. A dual disc up front, and a single disc in the rear. The main question remains what side of the bike the brake pedal will be. It seems, I cant mount anything for the brake system up yet until I find a motor. Well, excpet for the calipers at any rate.
When I decided to clean up the look of the bars...still planning on 6 bend pullbacks...I got to thinking what it would look like with only the grips on the bars. If the brakes are being controlled by the foot pedal, wouldn't it be cool to have the shifter and clutch together and off the bars where I could just reach and shift? Of course, that wouldn't work well with a right side shift Sporty. So again, it all boils down to the motor I get.
Leaving the clutch and shifting out of the picture for a bit, I can still lay out in broad general terms how the brake system should go. The brake pedal pushes the plunger in the master cylinder. The fluid goes up to the proportioning valve, and is sent off to the front and rear of the bike. The line going back runs to the rear caliper. The one line going to the front leads to a tee splitter, and each side has a line going to an individual caliper on either side of the forks. Outside of which side of the bike the master cylinder and pedal will be, this is the general layout of the brake system I want on Frankenbike.
I figure with this sort of set-up, I shouldn't have to worry about loss of traction from locking up the rear brakes when I jam on the pedal in an emergency stop. It should help keep traction on the front wheel in situations like gravel too. Because I have to admit, I dont always use my front brake anyway. I sometimes realize I am on only the rear brake after a second of so, then I apply the front. Or vice-versa. So having just the one brake will help on that as well.
I'm not doing this just to get the look I want. That is just a side benefit. The main reason, is so I can cheat, and get the braking I want without needing two separate systems to stop. The fact it cleans up the look of the bars is just a bonus benefit. I really can't see doing this for a big twin Harley, at least not a modern one. Not unless it has already been fairly stripped down, and is at least a semi-bare bones bike already. But that's not what I am working with. I'm working with a rigid frame, stripped down Sporty chopper. I like to go fast from time to time, but I prefer to be able to stop ALL THE TIME. So I can't see anything wrong with this sort of system. It's been around for decades, and the proportioning valves can be had for a reasonable price. I'll keep you all informed of how it goes as I get further along in the development phase. As for the clutch lever and shifter; well, that's a whole other story for down the road somewhere.
Catch ya on the road sometime...