Rear Brake for a Trike 1

[zaraf1]

Dear Community,

I am designing a loader-trike. The full laden weight will be around 800Kgs.
For rear axle, I am using some off-the-shelf parts from a small car with disc brake systems. These parts very basically placed in front-axle in that car. So I am just reversing the axles. For front I am using motorcycle fork also with a disc brake.
What I know is that in a braking system around 70 percent is provided by front braking due to load transfer. Now my question is if I could use just the rear-axle braking to completely brake the trike by not relying on the front motorcycle fork. I am not sure if the motorcycle fork will be able to handle that force at all?

 

[BrianPetersen]

You have to do your homework.

What's the load on the motorcycle fork, in the original motorcycle application, under max braking, taking into account the center of gravity height, weight distribution in the vehicle, and max available deceleration?

Don't go by rules of thumb. Do your homework. Establish the wheelbase and center of gravity location and do the math.

Broad hint: On my own roadracing motorcycle, with nicely warmed up racing slicks, I can use the front brake to raise the rear wheel off the ground. (edit:

https://www.youtube.com/watch?v=ttj16s4piQM

)

Now, re-do that exercise for your proposed vehicle and see what the various loading cases are.

As for relying on rear brakes only, hopefully you are not developing a high performance road vehicle that is expected to go very fast. Or an off-road vehicle that is expected to go down a steep hill on a dirt road and not end up in a pile at the bottom.

Not a fan of three-wheelers. A long-term friend put it well: all the bad things about a motorcycle, plus all the bad things about a car, plus a few more bad things of its own.

 

[GregLocock]

Single wheel at the front tricycles are worse in their own special way compared with tadpole trikes as well, think Reliant Robin vs Morgan. Ultimately it all comes down to CG height and in a cargo carrying application that is almost entirely out of your hands.

Cheers

Greg Locock


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[Lou Scannon]

all the bad things about a motorcycle, plus all the bad things about a car, plus a few more bad things of its own

Hahaha, good one! Reminds me of my Dad's saying (he was an RCAF and airline pilot), "An airplane wants to fly; a helicopter wants to crash".

"Schiefgehen wird, was schiefgehen kann" - das Murphygesetz

 

[dgallup]

What is a "loader-trike"? I'm imagining something like a 3 wheeled fork lift but I could be all wrong. How fast will this thing go? Where will it go? On road, off road, warehouse only? Need to know a LOT more about the application.

----------------------------------------

The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

 

[GregLocock]

I was thinking one of these

https://www.aliexpress.com/i/32948554767.html

Cheers

Greg Locock


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[GregLocock]

This is more fun

https://cn-motorcycle.en.made-in-ch...eap-Motor-Truck-Tricycle-for-Afghanistan.html

Cheers

Greg Locock


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[EdStainless]

If you are about to cross the street and one of those is coming don't step out. I have seen them with 1000lb of brick stacked on the back. They take about a week to stop, or until something breaks.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[zaraf1]

Hello gentlemen,

Thanks for your inputs. I would summarize the missing information:

1. Max Speed would be restricted to 80KMH.
2. From construction point of view very similar to

https://cn-motorcycle.en.made-in-ch...eap-Motor-Truck-Tricycle-for-Afghanistan.html

as someone posted.
3. It is meant for city usage for local transportation of passengers and goods.


As Brian mentioned I would check out the maximum braking provided by the motorcycle fork I am intending to use. And also would check all the load cases and transfer on the front fork. So if I correctly understand Brian, the crux is to solve the following:
1. to check the load transfer on front wheel. F= muxN, where N is the dynamic force
2. calculate the Torque on the wheel resulting due to 1.
3. calculate the Torque on the brake disc of the motorcycle fork.
4. For effective braking 3 should match 2.

Coming back to the theoretical question I asked. Can one just rely on rear braking or somehow optimize it?

 

[BUGGAR]

It's a tuk tuk! Entire families and their relatives ride through Bangkok on these.

 

[3DDave]

There is no optimization without boundary conditions. At best one can supply more braking to the rear than the rear can absorb, locking up the rear wheels. Most of my experience is one can rely on rear brakes to be relatively useless, but that is in the case where the center of gravity is in the middle of the vehicle.

 

[BUGGAR]

If you load this trike wrong, how will you keep the front wheel on the ground? I can see some wheelie bars being necessary.

 

[BrianPetersen]

You want that to go 80 km/h? "City usage" = being driven on public roads?

Where ("country" or "region of the world") are you proposing to do this?

The operating conditions that you describe would mean this vehicle would be subject to on-road motor vehicle safety and emission standards along with the relevant insurance and licensing requirements. Digging up the relevant motor vehicle safety standards, and establishing what you need to do in order to conform to the requirements in the region where you want to use this vehicle ... is the first exercise that YOU need to do.

I can say that a vehicle as shown in your illustration, and without a front brake, would have no chance of conforming to Canadian motor vehicle safety standards for a vehicle of this registration class ("motor tricycle" subset of "motorcycle").

Preserving the motorcycle's original front brake and using the motorcycle's original foot operated rear brake master cylinder to operate your new rear-axle braking system is conceptually the easiest way to do this. But, watch out for regulations. As soon as you venture out onto public roads ... you have to not only concern yourself with your own vehicle and your own safety, but that of everyone around you as well.

 

[zaraf1]

Hello Brian,

Its a "concept car" for me and would be intensively tested in close circuit before I make it street legal.

I will try to follow the braking strategy that you suggested. I am concerned if the rear brake cylinder from motorbike will build enough pressure to lock the disc brakes from a car. I thought instead of this, operating the rear brakes using the foot-pedal and regular car master cylinder. Hoping that the two unused cylinder outlets wont cause any problems or safety issues.

 

[EdStainless]

For unloaded or lightly loaded you will need the front brake as the rear will not have enough traction.
Heavily loaded you will front and rear and likely more.
In practice most of these have limited size front brakes, about what you would expect on a small lightweight motor scooter, and then fairly substantial rear brakes. When stopping the front applies first and as you brake harder you get both.
On a scale of 1-10 the safety of these systems to stop you is about a 2 or 3.
And don't get us started on stability issues.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[BUGGAR]

Maybe you should talk with the drivers of these things. My tuk tuk driver in Bangkok could corner on two wheels at will. (We all know forklift drivers who pride themselves on carrying a load on two wheels).

 

[TED7]

I don't have a great deal of experience with the design of automotive braking systems but I do own a car without ABS.

If I stand hard enough on the brakes to lock the wheels, the front wheels will lock first - this means that in a locked wheel scenario, I continue travelling in whatever direction I was pointing the car and no amount of steering input will change that until I come off the brakes and the wheels gain traction again.

If I were to mess with my brake bias to lock the rears instead, I would have no control over the rear end of the car when I lock the wheels, but I would still have steering. This means that should I be heading towards a pile of dirt, crash barrier etc, I would probably attempt to steer away through instinct and cause the front of the car to change direction, initiating a spin - leaving me with no traction on any wheel and still travelling towards the target but also with no chance of coming off the brakes to recover the skid.

I think bikes are the other way around, locking the front wheel will drop you to the floor, locking the rear just causes fishtailing. Trikes probably behave more like cars because they don't 'lean' and can't fall over.

I would highly recommend considering the effects of which wheel will lock when you consider your braking system, and ensure that it is the front wheel.

 

[BrianPetersen]

In the conventional motorcycle application, the front and rear brakes are independently controlled. (Right hand lever does the front brake, right foot lever does the rear brake) Thus the rider has control of what the rider wants to happen. See the video of the stoppie that I posted several posts up.

There have been some built with "combined braking systems" in which applying the front brake lever also applies a little bit of rear and/or applying the rear brake lever also applies a little bit of front.

Nowadays, they mostly have ABS, which has its own problems, riding on dirt or loose surfaces often requires partially or entirely locking the rear wheel to get the bike to do what the rider wants it to do; thank the regulators for that. Some of these systems perform the "combined braking system" function described above electronically.

 

[waross]

TED7 Locking the rear wheels of a car may give even less stability that locking the front wheels.
The older members will remember the original VW Beetles and the "Handbrake U-Turn".
A quick pull on the hand brake lever while moving forward and you were instantly pointing the opposite direction.

zaraf1 I would go with the master cylinder from the automobile. The master cylinder and brakes have matching characteristics.
I remember an SUV that had had the master cylinder replaced with the master cylinder of a much smaller car albeit of the same make.
The master cylinder that was adequate for a small car could not produce the volume of fluid needed for the much larger brake cylinders on the SUV.
The brakes needed to be adjusted about twice a week or there were no brakes.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Compositepro]

The steering wheels are all that control the direction of a vehicle. Locking the front wheel causes total loss of control, and will spin the car. The "handbrake U-turn" or "bootlegger's turn" is a controlled maneuver using the steering wheel and the hand brake. The hand brake locks the rear wheels so they skid forward around the center-point of the front axle, allowing for a much shorter turn radius than a not skid turn.

Locking the rear wheels on a straight road is not very dangerous. Locking any wheels in a sharp turn is dangerous.