Hi Friends. I am building a brakin 2

[Sweetdick]

Hi Friends.
I am building a braking system for rear brakes on a trike. This project is a 70's Triumph Bonneville, trike conversion with a modified Ford Falcon diff with Ford Falcon drum brakes. The basic rear brake system design so far is a 1" bore master cylinder with an inline flow control valve after the master cylinder to adjust away any brake locking.
Do you think this will work well? I can't think of any other way to go. I would appreciate your thoughts.
This is not my first rodeo. I am a fitter and turner and have a Cert III in fluid power (Hydraulics & pneumatics), I am not a guru but have a fair understanding. Your input would be appreciated.

 

[gruntguru]

The "flow control valve" you mention will need to be a proportioning valve. It will limit pressure not flow. And yes it will work.

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je suis charlie

 

[TugboatEng]

If you're going to use an industrial type flow control valve you MUST specify EPDM seals to work with brake fluid. OR, you can use a silicone DOT5 brake fluid. Even with the silicone fluid I still recommend EPDM seals.

Do you want a pressure limiting device? What if you do want to push harder to get a little more pressure in some unforseen situation?

A flow control valve can help as it prevents the jerk that may lock up the wheel initially.

Otherwise, the pressure in the system is determining the correct size master cylinder. This gives the option of being able to push a little harder on the pedal when you need to.

I strongly suggest converting to disk brake as they are much less prone to locking up. And don't get fancy with slotted or vented rotors. Bolt on kits start at $350 USD. Weld on kits are slightly less.

 

[BrianPetersen]

This type of vehicle has inherent handling and stability problems. Are you retaining the original motorcycle front brake on the handlebar with independent control of rear brakes from a pedal, as pet standard motorcycle operation? If so, then the rider is in control of front/rear brake bias, and no other flow or pressure regulation is necessary.

Look at your weight distribution and C of G height to estimate how much the front brake has to do relative to rear. Be on the lookout for difficulties, because you will find some.

 

[Sweetdick]

Thank you all for your help

 

[MintJulep]

Are the Falcon brakes self-energizing?

If so, I'd want to know how much and where, relative to the force you need, the self force comes in.

 

[Sweetdick]

I imagine they are self-energizing, although I have not yet had the wheels off it to check anything inside the drum. The idea of putting a bias valve/flow valve in the line after the master cylinder is to have some adjustment in the braking force. So, I have a one-inch master cylinder bore pushing fluid into the two rear Ford drum brakes, which I expect will be self-energising. Between the master cylinder and T-join to the 2 drum brakes, is a bias valve I can open from 57%-100%. the plan is to be able to adjust away any grab.
In theory, it would work. Thoughts?

 

[LittleInch]

The issue for me is that your Ford Falcon, as far as I can see weighs probably 1500 to 2000 kg? and brakes to match.

Your trike? Maybe 250kg?

So brakes more than a bit oversized. And flow control will do zero for you in terms of adjustment of braking force, only speed of action. The adjustment of braking force is your right foot. but even that might struggle between gentle slowing and a whole pile of smoke. IMHO.

what was wrong with two of the triumph rear brakes?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Sweetdick]

Thanks littleInch.
The brake lever is the only part of the rear brakes left on that project. I realize this plan may be overkill. Once the system is in place it may cause the wheels to lock. The idea is to wind out any wheel grab with the bias valve. If, as you say becomes a struggle between gentle slowing and a pile of smoke, then I would need to change to a smaller bore master cylinder. Is this correct?

 

[LittleInch]

Basically yes.

Not sure if you only have one brake lever or do you have a front lever and a rear foot operated pedal?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JayMaechtlen]

The car drums do have some self-energising built in, but shouldn't self-lock if you grab too hard then release, for example. Design/fab so you can change/adjust the mechanical advantage on applying the master cylinder. Then once you can conduct some tests, you can adjust the leverage as needed.
The only good thing about drums is they have provision build-in for parking.
Adjustable proportioning valves are available, if the same circuit is used for front and back you might want to use one on whichever end locks first.
A fair number of roadgoing trike/car hybrids have been built over the years, there should be some literature available.

Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[XR250]

That seems like a lot of unsprung weight for a trike. Gonna be hell on a bumpy turn.