h a l f b a k e r yGuitar Hero: 4'33"
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Haven't posted an idea for a while, so here goes.
This is something I coined for an electric bicycle or scooter, but could be used on any vehicle. If you find this idea on any load cell manufacturer sites, then they probably got it from me, since I sent them drawings for technical comments about
3 years ago.
I will describe for a motorbike as follows:
A twist grip is free to rotate except that it is locked in position by a small arm. If force is used to twist the grip, the arm is slightly bent. After the force is released, the arm returns to its normal position. A back stop prevents hairy arsed gorillas from bending the arm too much.
4 strain gauges are mounted on the arm, two to detect compression, and two to detect stretching. They are mounted in a wheatstone bridge configuration where temperature effects can be minimised. The strain gauges are connected to a simple low accuracy instrument amplifier which controls throttle position accordingly.
Zeroing takes place every time the ignition is switched on.
The sensitvity can be modified according to rider preference.
The rider keeps his wrist in the same position, regardless of throttle opening.
Drive by wire is quite common in motor vehicles: this is just an extension of the idea.
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If you feel like baking this yourself, I suggest that you dismantle a cheap digital kitchen scale. You get the strain gauge, amplifier and associated bits in a neat package. |
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Variation: A pseudo-suppository version that can be controlled by un/clenching one's buttocks. This might be better suited to braking, however. |
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I like it conceptually, but I wonder if it's practical. Something tells me that we're better equipped to maintain something in a given position than to maintain a constant pressure without the positional feedback. I'm not an expert though. |
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From a simplicity perspective: would a single strain gauge element with some sort of threshold/gating to handle the drift in the "off" position be sufficient? I think the feedback from the speed change would be sufficient and I doubt we're sensitive enough to notice that it now takes .5% more pressure to achieve 35 mph than it did when the temperature was 30 degrees cooler. |
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All questions aside, I'm tinkering with and idea where I'd like to implement manual speed control without markedly changing the hand position or compromising the ability to grasp the handle (which would happen with a lever type control). |
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[scubadooper], for an electric bicycle it is better because there are no mechanical wipers, and it's water proof. Furthermore, twisting the grip in the opposite direction can be used to apply regenerative braking.
For a motorbike, I restate what I already wrote: //The rider keeps his wrist in the same position, regardless of throttle opening.// and //The sensitvity can be modified according to rider preference.//
In my admittedly limited riding experience, holding a large throttle opening requires a tiring wrist position.
[phoenix], this novel braking system would almost certainly stop anyone from borrowing your bike, or nicking it.
[half], yes I think you may be right - one strain gauge may be OK since we don't need any degree of accuracy. A small deadband at the zero point would do the job. zero/span calibration during servicing. If the strain was controlled carefully, then there shouldn't be too much drift. P.S there are force sensors available on the market, but a single strain gauge is really cheap. |
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//holding a large throttle opening requires a tiring wrist position.//
I believe that some 'bikes have a throttle lock. Not that this takes away from the idea. |
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[angel], sorry, I forgot your suggestion at the top. Yes of course you are right. An indicator, too.
Didn't know about the throttle lock.. sort of like a cruise control, Eh? |
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When riding there's not really any force on the throttle you twist it to the position that opens the throttles (or injects the right amount of fuel) to keep you going at the speed you want to go at. The only force is minor provided by the spring return. |
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What you're suggesting is that whle I'm riding I need to be applying a moment to the grip, which to be senstitive enough to give me a fully selectable range of speeds from 0 to 150mph (or up to and over 200 on some bikes) must at the top end be quite a significant force. |
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That's definately going to be more uncomfortable than the current situation, where you have the ability to reposition your wrist (as I often do when travelling on motorways/highways). |
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In addition the current situation has better reliability, in that there is a spring return on the carberettors and a cable return on the throttle. |
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Good going for tryng to improve the world of bikers though! |
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[scubadooper], thanks for your comments. Yes, the normal way has a constant force/ variable position (if the spring return is designed well), and my idea is constant position/ variable force.
The force required does not need to be large, but I agree that some degree of differentiation between 10hp and 150hp should exist. A logarithmic response could also be used, where more control exists at the lower throttle openings, but wide open and 90% open are nearly the same force.
I cannot say if it will be ergonomically better without actually trying it.
A reference that I have mentions about "stiff stick" (yes!) controls- probably in connection with fighter planes. A stiff stick has been found to allow quicker tracking of a moving target in some studies. But the neutral position in this case has no actuating force. The reference goes on to say that not much work has been published on this type of control. |
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