Combining brakes to hand brake lever


Information and questions on GL1500 Goldwings (1988-2000)
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Shootdaroc
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Joined: Fri Sep 26, 2014 9:11 pm
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Motorcycle: 1995 GL1500A Aspencade Trike with Motor Trike kit

Combining brakes to hand brake lever

Post by Shootdaroc » Tue Oct 13, 2015 9:36 am



I have a 1995 GL1500 Aspencade with a Motortrike trike kit. As a disabled rider I am trying to combine most (if not all) of the brakes to the hand lever. Originally the hand lever only worked the right front disc brake. Last winter I had my mechanic route a new brake line to work the two drum brakes on the trike. He felt the hand lever master cylinder would support either the two front disc brakes or the two drum brakes in the back. I didn't think I would want both fronts only in an emergency situation, so opted to have the two rear drum brakes. I now find that the stopping power of only the rear drum brakes is not adequate. Not even as good as the original right front disc, so I need to add at least one front disc brake to the equation...

Has anyone accomplished this brake setup?
Is the Front master cylinder from a GL1800 bigger than the GL1500?
Could a right side delay proportioning valve off a GL1800 be used?
Any help would be most appreciated... Ron



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WingAdmin
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Re: Combining brakes to hand brake lever

Post by WingAdmin » Tue Oct 13, 2015 9:59 am

The problem you're going to have is just how much effort it takes to brake.

The hydraulic brake system is essentially a force multiplier. You squeeze the lever which moves a small piston a relatively large distance through its bore, pushing fluid down the brake lines.

This fluid then exerts pressure against two large pistons, which move a relatively tiny distance. Let's say you squeeze your lever with 10 pounds of force, and in doing so the lever moves 2 inches.

The piston in your master cylinder moves much less, because of the lever action of the brake lever. Let's say the piston moves 0.5 inches. 2 inches divided by 0.5 inches = a force multiplier of 4, which means the piston translates your 10 pounds of force into 40 pounds of force being exerted on the piston.

The piston travels 0.5 inches, and pushes fluid down to a brake caliper. There are two pistons in the brake caliper. The total area of the pistons (based on their diameter) is 1.5 square inches. The total area of the piston in the master cylinder is 0.05 square inches. 1.5 divided by 0.05 is 30, so multiply our 40 pounds of force by 30, and we get a total of 120 pounds of force being applied to the brake pads, simply by squeezing your brake lever with 10 pounds of force.

Of course, because the caliper pistons are that much larger, they move much less. With the master cylinder piston moving 0.5 inches, we divide that by the difference in area between master and slave pistons (40), which tells us that the pistons in the brake caliper move only 0.0125 inches. Fortunately, this is all that we need, because the pads rest almost right on the brake rotors - and moving only this tiny amount is enough to have them contact the rotor.

Now we add another brake caliper, which effectively doubles the area. We need twice as much fluid moving through the brake lines in order to move the second set of pistons the same amount. We can't double the lever travel from 2 inches to 4 inches, because our hands aren't that big! So instead we have to increase the size of the piston in the master cylinder - let's say we double it. Now in order to actuate the caliper pistons the same amount, and apply the same amount of force, we have to apply twice the force to the lever - 20 pounds instead of 10.

Now add two more - for two front calipers and two rear calipers - and we are well beyond what can be reasonably applied using your hand. This is what brought about the advent of "power brakes" in cars - essentially using vacuum from the engine to boost the brakes, reducing effort required from the driver.

So what is the answer? The GL1800 type system might be an option, if it could be adapted. It adds a second master cylinder built into a brake caliper, and the brake caliper is allowed to pivot. When the rider applies brakes, the caliper "grabs" the brake rotor. Because it can pivot, the brake rotor pulls the caliper slightly, which then pushes the secondary master cylinder piston into its bore, and this is what then actuates the other brakes. Basically you're using the bike's momentum as a brake booster to actuate the second brakes.

How this would be done, or if it could be done is a little out the scope of this discussion - you're talking a fair bit of custom fabrication and adaptation.

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Mh434
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Re: Combining brakes to hand brake lever

Post by Mh434 » Tue Oct 13, 2015 2:11 pm

Although I haven't researched them there are small power brake boosters for ATV's available. Maybe that would be an option...

Shootdaroc
Posts: 3
Joined: Fri Sep 26, 2014 9:11 pm
Location: Baltimore, MD
Motorcycle: 1995 GL1500A Aspencade Trike with Motor Trike kit

Re: Combining brakes to hand brake lever

Post by Shootdaroc » Tue Oct 13, 2015 3:39 pm

Let me first thank you (wingadmin) for the very quick and detailed reply. Not being a hydraulics major I thought the issue was volume, not pressure! Your explanation really puts a different twist on this modification.

It has also been suggested that we use a slave cylinder to actuate the rear master cylinder since it is already setup for the 2 rear and the left front brakes. I figured that it would be much easier to run connecting lines and maybe proportioning valves, but it sounds like it won't be that simple.

Lastly, I want to thank you for providing this forum. I have learned sooooo much from it about my bike and would never have gotten the Pingle electric shifter to work properly if I had not found out about the shifter brace. The how-to article on installing the brace was spot on and the photos were outstanding (as are all the how-to articles)!

As I was writing this I saw the suggestion on the power booster. Another good idea to look into. Thanks everyone for your suggestions. Somehow, I know it will work!!

Shootdaroc
Posts: 3
Joined: Fri Sep 26, 2014 9:11 pm
Location: Baltimore, MD
Motorcycle: 1995 GL1500A Aspencade Trike with Motor Trike kit

Re: Combining brakes to hand brake lever

Post by Shootdaroc » Sun Apr 15, 2018 4:17 pm

I decided to update this post with what I have "learned" through this process over the past 2 years in case it helps another disabled rider.
First, I failed to mention in the original post that the new brake line that the mechanic put on to the rear brakes was custom made, but from rubber. I could pull the lever all the way back to the throttle and the trike would stop, but could not even lockup the rear brakes for an emergency stop.

Here are the other options I tried to get the braking power I need:
1) Looked into getting a different bigger master cylinder or getting the original master cylinder bored out with a bigger piston to push more fluid. I couldn't find a bigger master cylinder from Honda that would work and didn't want a setup like the K2 levers. Couldn't find someone to bore out the original master cylinder.
2) Tried a double banjo bolt at the hand lever, adding the original right front brake line connected to the right front brake caliper. That made it slightly worse as the master cylinder could not push enough fluid for all 3 lines and I could easily pull the lever back to the throttle.
3) Bought a new OEM right front brake line to use with the double banjo bolt thinking the original may have stretched - nope!!
4) Took the double banjo bolt back off and put a 10 psi residual valve at the end of the rubber rear brake line where it goes into the steel line. That may have helped, but not noticeably.
5) Finally over the winter I replaced the rubber line going to the back brakes with a steel braided line and connected that to the 10 psi residual valve and can now lock the rear brakes up at will and can no longer pull the brake lever to the throttle!! Yeah...

Now, just because I can lock up the rear brakes doesn't mean it stops real quickly as you really need the front stopping power too and the trike weighs about 1200 pounds without rider(s). I now plan to try 3 more ways to get the front braking power added in the near future:
1) Try the double banjo bolt again at the hand lever with the original right front brake line connected to the right front brake caliper. My thoughts are that by using the rubber line and allowing it to stretch, the rear brakes will start braking first.
2) If the master cylinder can again not push enough fluid for all 3 lines, then get a steel braided line made for the right front brake caliper. I think the master cylinder can handle the volume if there is no stretching.
3) If that still does not do the trick, then put a 2 psi residual valve at the end of the steel braided brake line to the right front brake caliper.

This will hopefully give me the 2 rear drum brakes plus the right front disk brake to provide the braking power needed for those emergency stops that we all encounter a few times a year!!



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