I plan on running a handbrake in my hambster, and I am having problems getting the ratio right. I started out with a 5-1 ratio and was told I needed to be a t 2-1. I thought it sounded strange, set it up at 2-1 and now I do not have any brakes. I do have some, but it would take a gorilla to push the lever hard enough to stop the car. I'm running a Wilwood master cylinder with a 1" bore, 3/16" brake line all the way, to a ranger rear end. I know some of the guys were running hand brakes. I need to know how long your lever is, where the pivot point is located, and the distance of the master cylinder from the pivot point. Once I get this, we are headed to the track to get some numbers!!!
I too run a hand brake that I set up. From the pivot point to the clevis is 2" and the handle is 23". I use the 7/8 VW master cylinder. Are you running Drum Brakes?? Don't forget the residual valve.. I think it has to be like 8-10 lbs.for drum and 2lbs for disc. What is prolly happening is all the fluid is running back into the cylinder. The R valve stops that.. Just my thoughts....
Here is our set up. Its a Model A Ford Factory emergency brake handle. The handle is 18 inch long, pivot point is 2 1/2 inches up from lower hole and brake rod is 4 1/2 long. Using the tilson cylinder. It seems to work very well on jack stands stoping and holding the car. Havent had her on the ground moving yet.??
Here's ours,handle is 27''long pivot point is 5'' below clevis. I noticed you said you would have to push your lever, ours you pull much easer than pushing. Brakes works good, On tracks with shorted shut down you just have to puuulll harder.
Also, I have always been under the ***umption that pulling a brake handle is safer than pushing because it keeps the inertia of your body from pushing harder than you intended and locking up the brakes.
Thanks for all of the replies. After doing some searching on the internet, hand brakes should be between 11 and 13 to 1 ratio. ThingyM is closer to that than anyone elses that posted. I'm not saying anyone else's does not work, just relaying what some drag racing websites have to say. Jim, I understand what you are saying about pushing instead of pulling. I don't think I will have too much body inertia pushing on my handle, strapped in a five point harness. I was thinking that I could use what little inertia there is to help me stop the car. I could set it up either way as I am now going to have to redesign the way I have it set up. I drove the car down the road last weekend and had no problems with pushing the lever, I just did not have it set up to stop the car. The only reason I can see to set it up to pull, would be that you can probably pull more than you can push strapped in.
Mudflap, I realize that I can not do that. I have brakes that work, I just do not have the leverage on the handle to operate them correctly.
From Ken Lowes web site: trouble shooting brake problems. MASTER CYLINDER The bore size of the master cylinder influences the obtainable line pressure. Normally, when using only rear brakes a 7/8'' master cylinder is needed. If single piston front brakes are used in conjunction with rear brakes a 1'' master cylinder will work. For using 4 piston calipers front and rear a 1 1/8'' master cylinder is recommended. BRAKE PEDAL RATIO Improper pedal ratio is the most common cause of poor operation of brakes. The pedal ratio must be great enough to produce 1200 PSI system pressure under severe braking conditions. We recommend using a pressure gauge connected to the system to verify the maximum available pressure before running the car. Start with a pedal ratio of 6:1 and adjust if needed.
What is the multiplier used to convert from foot power to arm power? I would think it would take a bigger ratio when you use a hand brake, it is a differenet mussel type.
REJ:: I tried to get back with your mail but pushed something wrong Poooofffff all gone. Will get in touch when we get back from Testing this weekend and then the March Meet next weekend..
REJ, Not only do you need to consider the ratio of the brake handle but you need to consider the ratio of the master cylinder/wheel cylinder combination. I'll explain but, it may get a little long winded. Calculate the area of your master cylinder and wheel cylinder: Master cylinder bore 1.00" 1 x1=1 x .7854= .7854 square inches If the wheel cylinder is also 1.00" the ratio of master cylinder to wheel cylinder is 1:1. Therefore whatever pressure you push on the brake handle will only be multiplied by the ratio of the brake handle. (Typically about 6:1). That means if you push the brake handle with 100 pounds of force the wheel cylinder will only put 600 pounds of pressure on the brake shoes. Now consider if you reduce the Master cylinder bore to 1/2 inch (.50) .5 x.5=.25 x .7854= .19635 square inches. .7854 divided by .19635= 4 Now the ratio of the master cylinder/wheel cylinder is no longer 1:1 as it was when you had a 1" master cylinder, it's now 4:1. Multiply the ratio of your brake lever (6:1) times the ratio of your master cylinder/wheel cylinder (4:1) and the overall ratio is now 24:1. Now when you push the brake lever with 100 pounds of force the wheel cylinders will put 2400 pounds of force on the brake shoes. Remember, make the master cylinder smaller and you'll have more braking with the same brake lever ratio. I hope this helps. Ron
Well, I installed a new handle that measures out to 12:1 ratio and now I have plenty of brake. I could probably lock them up if I tried and that is the way I like them. I really do not think locking the rear brakes up at 100mph is a good idea. Thanks for all the replies, all of the informatiion is good. I had most of it, but did not know the correct ratio to have on a hand brake. The 4:1 and 5:1 ratios are great for foot brakes, but not worth a **** for hand brakes. If you think about it, your leg has the strongest muscle in your body and the ratio does not have to be that great to be able to stop the car. Now if I could bench press 700-1000 lbs, I probably would have no problems.
Actually, We've devised a simple system to run both foot and hand actuation of the master cylinder, independant of each other. With multiple drivers it seemed having the option at hand (pun intended) was desirable. Thus we'll have three pedals and a lever. We did however, decline our further suggestions of hand throttle and hand clutch options. So, no twist or squeeze grip on the steering tiller.
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