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Designing Braking/Accelerating System

08/22/2017 7:25 AM

I have designed an handcart that is to be powered by an engine. I would like it to have a provision such that when the operator releases the accelerator, the brakes engages immediately but I don't know how to go about it.

Any help will be appreciated.

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#1

Re: Designing braking/accelerating system

08/22/2017 7:33 AM

<...handcart that is to be powered by an engine...> What an unusual concept.

The statements <...don't know how to go about it...> and <...have designed...> cannot both exist simultaneously.

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#2

Re: Designing braking/accelerating system

08/22/2017 7:43 AM

By that I mean I know the power requirements and major specifications. The issue is having a provision where the brakes automatically engage when the accelerator is released. Should I call it fail safe????

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#3
In reply to #2

Re: Designing braking/accelerating system

08/22/2017 7:49 AM

One might call it a single control application, perhaps.

  • Many rotary lawn mowers have a facility that turns off the engine when a control is released, thereby bringing the equipment to a halt.

In an environment where it is second nature to depress a brake pedal with a foot to apply the brakes on most road vehicles while seated therein, training of the operative to operate the vehicle correctly may prove to be the biggest challenge.

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#4

Re: Designing braking/accelerating system

08/22/2017 9:40 AM

May I suggest that you have an idea, but you don't have a design?

If you can't follow through with the adaption of a fail safe brake, how can you possibly comprehend any and all of the other design elements?

If your pockets are deep enough you can have 'your design' brought to fruition and feature it for kick starting and Gizmo web sites etc. Ad nauseum.

... that should be about as clear as your question

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#5

Re: Designing braking/accelerating system

08/22/2017 10:09 AM

This is a very simple design. Designing a modern braking system is far beyond your capabilities.

Start here and refine the idea as needed.

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#9
In reply to #5

Re: Designing braking/accelerating system

08/22/2017 11:38 AM

well, relatively good idea, though old school. That's my thoughts though.

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#6

Re: Designing braking/accelerating system

08/22/2017 10:29 AM

It seems like if you have a cable to open the throttle, you need another cable connected to the same control (lever, pedal, etc) to release the brake, which is held engaged with a spring.

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#15
In reply to #6

Re: Designing braking/accelerating system

08/22/2017 5:38 PM

I seem to remember some golf carts used a system very much like that. Single pedal, push down to release brake, start engine and apply throttle and when you wanted to stop, you would slowly lift up and the pedal would rise, closing the throttle, then killing the engine and then gradually applying the brakes as you lifted your foot.

The problem with systems like this is that you can only get as much braking force as the return spring on the mechanism. You can't 'stomp' on the brakes for an emergency.

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#16
In reply to #15

Re: Designing braking/accelerating system

08/22/2017 5:59 PM

I'd be surprised if such a drive system was on anything that the public was allowed to drive.

Especially golfers who had had a few too many.

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#23
In reply to #16

Re: Designing braking/accelerating system

08/23/2017 9:37 AM

Yes, I concur, I believe that any such push cart motorized will need an automatic arrestor system that applies normal braking, then will lock the wheels at a slow enough speed not to tip the cart over. There will also be a mandatory manually applied stronger braking system to stop and lock wheels, so no runaway situation develops.

If releasing the throttle kills the engine, and the engine is a positive drive system, will that serve as at least part of the automatic arresting system?

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#7

Re: Designing braking/accelerating system

08/22/2017 10:49 AM

The brake is applied with spring load. When the accelerator is depressed, a lever attached to the accelerator rod releases the brake.

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#8

Re: Designing braking/accelerating system

08/22/2017 10:55 AM
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#10
In reply to #8

Re: Designing braking/accelerating system

08/22/2017 11:40 AM

Well done! No point in saying much else. I will not mention He Who Must Not be Named, to prevent the sudden death of this thread.

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#11
In reply to #8

Re: Designing braking/accelerating system

08/22/2017 11:43 AM

That exactly what I was looking for. My concept is way close to this. The information is helpful. Kudos!

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#12
In reply to #11

Re: Designing braking/accelerating system

08/22/2017 12:34 PM

Now you just need to incorporate these stair stepper wheels into the design...for climb stair mode...

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#13
In reply to #12

Re: Designing braking/accelerating system

08/22/2017 1:33 PM

Aren't both things you mentioned still under patents? I would suspect they could be.

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#14
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Re: Designing braking/accelerating system

08/22/2017 1:45 PM

There's room for more original ideas here....as always a patent search would be required for any thoughts on commercialization...

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#17
In reply to #12

Re: Designing braking/accelerating system

08/22/2017 10:35 PM

Second pic seems to be a copy of the Schaeffler lightweight diff?

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#20
In reply to #17

Re: Designing braking/accelerating system

08/23/2017 12:42 AM
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#22
In reply to #20

Re: Designing braking/accelerating system

08/23/2017 4:47 AM

Yes I was 'almost' correct - ;-) - x that for planetarys to act as a diff, you need planets to be in pairs, to provide the reversing action.

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#18

Re: Designing Braking/Accelerating System

08/22/2017 11:13 PM

The problem with linking the throttle to the brakes is that both have varying degrees of applied torque/anti-torque. You don't want to have a partial throttle and a partial brake applied at the same time. That's like stomping on the brake and flooring the accelerator at the same time to give your auto-tranny a hemorrhage. If your system is still in the design stage, I'd recommend a worm-gear driven drive. They're "self-locking". The worm gear can go in either direction at any speed and the driven gear cannot reverse power the worm gear. Therefore, the driven gear only turns according to the throttle's speed/direction.

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#19

Re: Designing Braking/Accelerating System

08/22/2017 11:16 PM

Many years ago I took apart what was left of some odd small engine drive gearbox unit apart that used a odd but interesting combination automatic clutch and brake mechanism in one unit.

I don't know what it was originally was used for (powered wheelbarrow or tub cart was my guess) but the way the centrifugal clutches were set up was that at idle the brake would set via spring loading and as the engine RPM's went up the centrifugal weights for the brake assy counteracted the springs then once the RPM's were high enough the centrifugal clutch took over and started moving the gear shaft to the transmission.

I think, or at least that was the impression I got of how it worked. It was a simple High - neutral - low - neutral - reverse gearbox and from what I could tell the automatic brake only worked in gear. Lots of pieces were missing and it was rusted up beyond reasonable repair so it eventually went out for scrap.

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#21
In reply to #19

Re: Designing Braking/Accelerating System

08/23/2017 4:35 AM

That's a really sad ending. Awesome info there. Thanks

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#24
In reply to #21

Re: Designing Braking/Accelerating System

08/23/2017 4:00 PM

I wish I would have kept it now but at the time it was just an odd item that came from a pile of junk I bought at an auction for a few dollars.

It was pretty beat up and rusty and i had no real use for it. Especially given what was broken and what else was likely missing as well.

Now I have the tooling and skills to have rebuilt it but still it was just an old novelty at best.

Just something for you to think about.

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