Synchros

Given a source of 12 VDC and one of 110 VAC at 60 or 400 Hz, how might synchro operation be established between the driven wheel of a bicycle or tricycle and the free (nondriven) wheel(s) for all-wheel drive?

IIRC a synchro is a rotary VDT (variable displacement transducer) or type of transformer. They were used in airplanes (long ago?) to connect the steering yoke to flight control surfaces (ailerons, elevator, and rudder)

The reason I ask is I have a Kinetic Energy Recovery Bicycle group on LinkedIn. Any of you here would be welcome there. Our goal is to save lives and smooth bicycle/automotive traffic interaction with regenerative braking of bicycles/tricycles as they approach a stop, including "winding up some joules" while stopped (applicable to trikes) by backpedaling. With energy on board, extending the development to all-wheel drive seems a natural next step--for a different purpose and market, though.

We've discussed magnets in the rim and an arc of electromagnets along an arc near the rim, as one method of drive, and then I though, that looks like it could be a synchro. Without a synchro, we'd have to measure the torque at the pedal driven wheel, and control power input to the electric wheel(s)...way too much trouble, like building an ABS from the ground up. We can assume our trike has 3 same-size wheels.

There's no reason to reinvent...the wheel. (giggle)

Douglas (Dana) Goncz Replikon Research Seven Corners, VA 22044-0394

Reply to
The Dougster
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I looked up synchros and found they usually relay position. They don't usually control a load unless an amplidyne is used.

From the Wikipedia:

"How an amplidyne works

An amplidyne is a special type of motor-generator which uses regeneration to increase its gain. Energy comes from the motor, and the power output is controlled by changing the field current of the generator. In a typical generator the load brushes are positioned perpendicular to the magnetic field flux. To convert a generator to an amplidyne you connect what would be the load brushes together and take the output from another set of brushes that are parallel with the field. The perpendicular brushes are now called the 'quadrature' brushes. This simple change can increase the gain by a factor of

10,000 or more."

More recently, power FETs are used.

Doug

Reply to
The Dougster

You don't need to sense pedal torque, the driven wheel either has enough traction or it slips. When it slips you have a speed difference between the wheels that you can sense and correct. You don't need to accurately measure the difference, just null it out.

The All Wheel Drive on my car detects a difference between front and rear axle speed and connects power to the rear axle proportionally to the difference. Each axle drives a pump that moves hydraulic fluid in a circle. A speed difference lets pressure build up and operate a clutch cylinder. There's some allowance for cornering and driving in reverse but it's a simple concept that works very well.

For an electronic version you could sense wheel speeds as DC voltages, subtract the main and slave voltages and power the slave wheels proportionally to the difference, with a small dead band. You'd need PM motors etc for tachs to sense speed, a low-gain op amp to compare them, and an H bridge or PWM controller for the slave wheel motors. And a kill or dead-man switch.

I love the irony of printing KILL KILL KILL KILL on the label maker when I'm assembling *safety* equipment.

My truck has an all-mechanical 4WD with no center differential, both axles turn at the same speed. In very slippery conditions both work well, any difference is masked by the different weight distributions. In marginal conditions the AWD slips a bit before the rear axle engages but I don't feel it, only hear the tire noise. There is no feedback to the steering wheel. At speed I think stable steering is more important than maximum traction, having owned a Civic that oversteered on ice.

Ever ride a dirt bike on a slippery surface? If the rear drive wheel can slip you don't have much steering traction either. When you brake enough that the front wheel slips you go DOWN.

A three-wheeler with an electric motor driving a rear differential might be easy to do and work well. Separate wheel motor drives would give you dangerous steering problems at more than lawn tractor speed. Once you go fast enough for wheel hop things can become complicated.

ABS is really simple until you add on all the fail-safe circuits. I built the test stations for the first analog electronic ones in the

70's.

jsw

Reply to
Jim Wilkins

Actually -- the synchros which I have seen/used don't have enough torque to do what you want, nor do they have enough to control the flight surfaces.

They were good at feedback from the remote control surface to tell the controller what position it has reached, so the servo motor (a different thing) could be told to keep trying until it got there. Best is to power one end's rotor with the AC, and compare that voltage to the voltage induced in the rotor at the other end. The difference will be zero when the two are pointing the same direction. Amplify the difference and use it to power the AC servo motor to position things. Still not what you really want on what you are building.

Smaller ones were used to drive pointers in navigation instruments.

I guess that a synchro *could* generate the torque you need/want, but the total size and weight would make it a losing proposition. I picture one perhaps four or five feet in diameter, and maybe 8 feet long to do it with 60 Hz. A bit smaller at 400 Hz, but you still have to generate that much power.

An interesting approach -- but I doubt that you could get enough power through it. They really are not designed for power -- just for driving things like a compass card, driving it from a gyrocompass (the

60 Hz ones used by the Navy once upon a time.)

I think that perhaps you do need to do just that. The drive from coils next to the rim might work for other types of motors, but not for synchros.

Enjoy, DoN.

Reply to
DoN. Nichols

Don, there were basically three types of "Synchros". Generators, Motors, and Control Transformers.(CT) The ones that used an amplifier and servo drive motor were the CTs. That is what was used in PPI scopes to control the rotating yoke. (I forget the size designations) The Generators and Motors would produce a fair amount of actual positional force. The Generators were not as suitable for an output end as they were not damped, but the general config. was the same as the motor. (I had a pair of those from the surplus when our outfit was broken up in

1952 and may still be in the "milk house" in PA) The CTs were constructed with a completely different rotor and could not be powered like the motors. Finally something I have had experience with. :-) ...lew...
Reply to
Lewis Hartswick

FWIW, I have a pair of 60 hz synchros here - if I tie the x,y,z leads together and also parallel the excitation leads, one syncrho will follow the other nicely - and the torque is enough foot pounds that it's well nigh impossible to hold - these units are about 8 inches long and 4 to 5 inches in diameter.

This would most assuredly be one of the last ways I would attempt to achieve all wheel drive -it is horribly inefficient, very expensive for the large syncrhos and very heavy - a much more standard solution would be to just use three separate DC or AC motors

Reply to
Bill Noble

Syncro's are sense and transmit the same rotation.

I have several sets - some very large.

I'd think they could be on a steering wheel and then hydrologists then slave power from another source to the small control power making the distant and resistant to move actually do it.

e.g. flight control surface. Drive or sense where it is and feed it back.

Torque on one won't consider driving a wheel if someone is sitting.

Martin

The Dougster wrote:

Reply to
Martin H. Eastburn

It sounds like they want to steal power through the synchros and drive another wheel. Using lots of power for the core that transfers to the other.

It is an idea, not a good one for a project like this.

Mart>

Reply to
Martin H. Eastburn

But they wre never intended to move control surfaces. Just instrument indicators.

Controls take *torque*...

Reply to
cavelamb

I am old enough to remember when the Schwinn Varsity was panned by all the bike aficionados because it was a few pounds heaver than the whizz bang French, Italian or Japanese bicycle.

Now you are suggesting to add weight so that after you pedal up the long grade you can recover some of the energy when you are going down hill to make it easier to go up the next hill.

Unless I am missing something, seems to me you will be expending more energy to go the same distance on your ride.

Reply to
Roger Shoaf

I think the improvement would come if you could capture, store and return some of the energy that is dissipated as heat when the cyclist uses the brakes. Being able to recover the energy might encourage cyclists to not just sail through stop signs and to maintain more reasonable speeds on down grades. For example, imagine a flywheel that would spin up when you are stopping for an intersection or going down a long grade. Then you could use that energy to boost yourself back up to speed. Sort of a hybrid.. and the weight added would be much less than if you tried to power the bike continuously.

If you seldom touch the brakes, it's not going to save anything significant.

Best regards, Spehro Pefhany

Reply to
Spehro Pefhany

I understand what he is trying to accomplish, but it seems to me that there are several problems that might be very difficult to overcome. First off lets say you were able to store energy in a flywheel. First you will have extra energy expended to pedal the flywheel up the hill, then you are at the bottom of the hill stopped and have a big old gyroscope that will create mischief if you need to change direction. I seem to recall that this flywheel idea was tried in automobiles and abandoned for that reason.

Next, if you were to try to convert the wheels of the bicycle into a generator, then attempt to store the electricity into batteries, you have some practical problems as well. First off you increase the weight requiring more energy to be expended going up the hill. Next your generator will be operating at a whole lot of different speeds and that is going to be a real pain to efficiently regulate the voltage to charge the batteries.

Think of how much weight and space it would require to have enough battery power available to go up hill at any decent rate of speed. Now think about having to pedal that weight up a hill or even drag it around on the flatland. Seems to me you are going to pay too big a price to get little in return.

Just my 2 cents.

Reply to
Roger Shoaf

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