Servo-Operated Throttle

Hi,why not use a two cable system similar to what is used on dirt bikes.The spring tension will be lighter and the second cable will guarantee the throttle returning.

I recommend against potentiometers, as they generally can't handle the vibration for very long -- especially the film types, whether thick or thin film. Wire-wound pots last longer, but, there again, won't handle vibration for a long time.

Optical encoders are your best bet, and one needs to be chosen with fairly low resolution, again because of vibration. Incremental quadrature encoder is required so that direction can be ascertained, or one may use an absolute encoder with perhaps a little higher resolution.

I would also recommend a brushless DC servo motor, so that vibration doesn't wear the brushes out, and also so one doesn't have to depend on the integrity of brushes in order for the throttle to work properly.

As with any system that deals with life safety, I highly recommend that the system design ensures that failure of any component results in shutting down, or at least returning throttle to minimum.

More info if needed -- I spent ~25 years designing servo control systems for one thing or another.

Harley-Davidson is currently using "Throttle By Wire". Maybe something can be learned by studying their system.

check BMW... they have been using "drive by wire" for almost 20yrs i had them on my V12's and they rock!! the throttle motor setups are better on the "newer" (95-2001) 5.4 ltr motors as far as response (i will cross 200K miles on mine sometime next week) but the one on my 89 was original @224K and i had very few probs w/them..... instead of a small block chevy why not try a v12? takes up about the same space and if you've been riding for a long time the torque band would remind you of the old 3cyl Yamaha's a little poochie off the line but when you hit the magic number wave bye bye....hehe

Before using an electric servo, look at two servos you already have from when the engine was on the pickup truck.

The least bulky and lightest weight will be the vacuum boosted power brakes. If you can easily adapt a wheel cylinder to pull on the throttle cable - this might do the job.

The other servo system that you have is the power steering. Leave the power steering pump on the engine, and see if you can adapt the hydraulic servo on the steering gear to pull the cable.

I will be using a servo throttle on my prototype trike, but in it there is no direct connection between engine and wheel, (the wheels being driven by electric motors) so if the system fails, the only hazard is that the engine will overspeed -- but that is prevented by other means.

If a servo is used to control an engine that is directly coupled to the wheels, then it must be very thoroughly designed, and I would recommend lifting a drive by wire system from an existing car... but that alone can be complicated, because you can quickly find that you need the entire engine, the ECU etc.

For simplicity and safety, I like the recommendation in the first post to lighten up on spring tension and use dual cables. Also, use high quality cables, so that there is little friction. But even so, you have a lot of load to overcome: a foot throttle may be the best bet.

I'm using a standard holly four barrel carburetor about 550 CFM single pumper. The engine is a stock "87" 350 from a pick up and I'm running an "87" Th200 4R trans with factory kick down linkage (cable).

As you probably know, (because you mention it) this setup is the basic problem. In a modern engine, there is no kickdown cable, no accelerator pump, there is no progressive action with the linkages from one pair of barrels to the other. A modern engine's throttle plate can be operated by hand. Old Honda Gold wings were sometimes hot rodded with twin Weber two barrel carbs, which can also be operated by hand.

The secondaries could be operated by vacuum, (if they are not already) and kickdown could be servo operated (so that only a micro switch needed to be operated by the hand linkage) but I would avoid servo operation of the throttle proper, unless you can lift a fully-engineered system from a car.

Having said that, hall effect throttles are available for electric motorcycles (the link is typical, but you can find many -- Magura, of traditional motorcycle fame, makes one too). These are more reliable than pot-based throttles. There are, no doubt, servo drives from linear actuator providers that would interface directly with a hall sensor throttle (0-5v output). But remember, especially with an auto trans, an unintended full throttle event can be deadly to you and others. You would do well to read the Federal Motor Vehicle Safety Standards regarding throttle operation.

But really, I think you have already found a good solution -- a foot throttle. With auto trans, you are not using a foot to shift, so you might as well use it for throttle.

You are making my head smoke. There are parts that have not been used for too many years. In my younger years I would see Hydraulic throttles used on drag cars. As I recall there was a small hydraulic cylinder attached to the gas pedal, and a matching one on the carb. They were onlt about 1/2 to 5/8 " around, and connected by 1/8 nylon tubing. Filling with oil or brake fluid would allow near 0 friction. Try searching some automotive or marine speed shops. Good luck.

I did a search of hydraulic throttles. There are about three available units that showed up early. You might have to activate the foot throttle with your cable throttle, but the rest should be a piece of cake compared to the rest of the construction.

Back when I lived in the Great Lakes area, I rode my motorcycle through the winter. My mitts tended to slip a bit on the twist throttle. This was 40+ years ago, so snowmobile technology was not far advanced. My lined leather mitts were wrapped in a folded towel, and the whole thing slipped into a 5 pound sugar bag (6mil poly) for good insulation, but minimal dexterity! I hose-clamped a metal bracket to the throttle handle. I could use it normally, or rest my palm on the top of this bracket, near the start button, pulling or pushing on the end of it, for fine positive throttle control.

I would suggest you enhance the throttle or use the simple hyddraulic system before re-inventng the servo thing.

Good luck!