Brakes..!?!!

OK, here is my story on the back brakes on my trike. When I took my trike for the first test run everything worked fine except... well you guessed it.. the rear brakes. I had installed a 1960 Ford master cylinder, I thought it would be perfect, one line output and big enough to stop a Truck. Boy was I wrong, I had little to NO brakes and the pedal was stiff as a board. I thought the original Master should do it, so I bought a new ($60) VW Beetle Master Cylinder. The brakes where a little better, but still far from good. The brake wheel cylinder where new, so where the shoes, the adjusters and the brake lines. Basically everything from the master cylinder to the wheels have been replaced. So what's the problem?? Here I quote Trader and Lloyd who can explain it better.
 

The ratio of the diameter of the plunger in the master cylinder to the 
diameter of the piston in the slave or wheel cylinder has EVERYTHING to do 
with braking. If the diameter of the plunger in the master cylinder is 
greater than the diameter of the piston in the wheel cylinder you won't have 
any brakes because you have no advantage. Also the distance between the pivot 
point of the brake pedal to the footpad is very important. The longer the 
pedal the more mechanical advantage you have. The bore of the master cylinder 
should always be smaller than the bore of the slave cylinder. You pick up the 
extra fluid to operate more than one wheel cylinder by the simple fact that 
the stroke of the master cylinder is much more than that of the slave 
cylinder. The rear brakes of a VW are weak at best. If everything is not just 
right they don't exist. 
TRADER

 
Ok, here's the deal.....  Brakes are a simple hydraulic system.  You want all the surface area
advantage you can possibly have.  Let me try to explain this in a different way then Trader,
even though the out come will be exactly the same.
Assume:
    2 wheel cyl.'s w/ a surface area of 1 inch each = 2 inches total reacting surface area
    1 mstr. cyl w/ a surface area of 1/2 inches       = 1/2 inches total acting surface area
    If each wheel cyl. must move 1/2 inch to lock up the brakes you have a  volume
change of 1x1/2= 1/2 in each cyl, which = total volume change in bot wheel cyl.'s of
1 cubic inch ( assuming the are single acting wheel cyl.'s.
In order for the master cyl. to "move" 1 cubic inch of fluid it must travel (move) 2 inches
(1=1/2xV; 1x2=1/2x2xV; 2=1V; 2=V; V=2).

I hope this helps.  Obviously it is simplified and assumes alot, but that's the easiest way of
figuring something out.  I hope I didn't upset anyone or make them feel bad or stupid, as
that's not what I am trying to do in any way.  For me it only makes sense once it's put on
paper.  Hopefully leverage (the pedal) is understood.  The better your advantage the easier it
is to push the pedal, leverage and surface are theoretically accomplish the same thing... it
takes alot of advantage!!!  Just for kicks, ask how many psi it takes to make the brake system
stop a vehicle!

Lloyd "Meat"

OK. now I know... but what can I do about it? First thing I thought was, "well if the Master Cylinder is missing to operate four wheel cylinder I'll give him four to operate. My idea is ( haven't tried it yet ) to connect two extra 'blind' wheel cylinder to the system. The only function those two would have is to give the master cylinder the volume it needs. I would restrict both sides of the wheel cylinder to prevent the pistons from popping out and mount them where they are not in the way.
My second idea is to connect the front brakes ( 500 Honda Dirt bike fork and brake ) to the Master Cylinder. I have done this and it works well. I have more brake power because of the added front brake but the back wheels still don't have more brake power.
My next step is to connect one, maybe two 'blind' wheel cylinder and see what happens. If this does not resolve the problem I will try to use a Clutch Cylinder. All this will happen within the next two to three weeks (today is Monday May 3rd, 1999), so stay tuned...

Gunnar


Tuesday May 5th, 1999
Ok, I am trashing my 'blind' wheel cylinder idea due to some email I got which make sense to me. Thanks everyone for sending email about the Brake subject, there are some real good tips and info coming in! This weekend I will take a real good look at my brake system and hopefully with the tips, ideas and my thinking cap come up with a solution... See you back after the weekend.

Gunnar


Wednesday May 12th, 1999
My solution:
Please keep in mind that this does not apply to everyone who has brake problems.
My setup is: Original (VW) single circuit master brake cylinder (one outlet for the switch, one for the back brakes and two for the front). Original drum brakes, overhauled wheel brake cylinder, new brake lines, new shoes.
My problem was a stiff brake pedal and hardly any brake power. The cause for this was a too short brake pedal. My brake pedal, mounted on the bottom of the frame (see MyTrikePage) was eight inches from pivot point to the pedal and two inches from pivot to brake cylinder rod.
As it turned out that was not enough leverage and I extended the pedal another six inches to the total of fourteen inches.
Brakes are great now, all that's left is to install a pressure device to the front brakes (front and back brakes are controlled from the master cylinder). It will allow full pressure to the back wheels and about thirty pounds to the front. Some people install the front wheel cylinder for the back brakes. Supposed to help with a bit more stopping power. Haven't tried it, Will try it in the future, right now I just want to get the trike on the road. Enough building for now...exept I still have to convert to hydraulic clutch because my clutch cable broke and I don't want to get a new one every time I step on the clutch, and then there is still......and......and...........
There you have it, if you have problems with your brakes make sure you have enough leverage with your pedal....

Thanks again to everyone who send me emails with suggestions, tips and solutions!!

Gunnar


 
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