golf cart steering

[cg285]

i am not a robotics guy. i was directed here from "practical machinist forum". my son has recently been released from a hospital where he spent 7mo w/life threatening burns. he is now able walk some but has no use of arms/hands. he has given me the task of coverting his golf cart to foot/leg controls. (all reasearch on existing handicap stuff relates to hand controls only)
i need some suggestions for steering. linear actuators was mentioned but the supplier says no as they are 20% duty cycle.
any ideas?
thanks, cliff

[JamesCH95]

Best wishes to you and your son.

A hydraulic ram steering system, typical on 4x4/off-road vehicles, would be very effective but are moderately complex and heavy. Could be foot-operated with either a lever or pedal.

Where are you located? I would wager that you aren't too far from a FIRST team, and they would probably be willing to help you directly if you wish.

[cg285]

i'm near orlando, boy & cart are in virginia beach

[DonRotolo]

OK, so do we find you a team in Orlando, a team in Va Beach, or both?

Also, before we start: We are a bunch of practical guys, some engineers, some not, and a LOT of High School kids, here on this forum. You and your son need to be the final deciders if something is safe or not.

OK, let's understand the problem: He has some use of his legs, but not his arms or hands. That means to me that he can use throttle and brake, but not steer. Is that right?

Going on that assumption, if the right foot is go/stop, the left foot needs to be steering.

Problem #1: How does the left foot control steering. That is, does one use a gas pedal type control (press for right, pull for left) or a side-to-side lever? I would hesitate for a push/pull arrangement, since a big bump could cause an inadvertent turn. But, think about your son's capabilities and let us know what you think.

Problem #2: OK, we have some kind of input, how to we physically move the steering wheel?

A linear actuator directly on the steering box sounds nice, but as you said most are really not suited for that - but check McMaster.com and Google for other styles that might be workable.

Pneumatics are right out, since they can't hold a given position (Air compresses)

Hydraulics are fine, but need a pump for pressure and some plumbing. You don't need a lot of power (= thin cylinder, maybe 1" or so), but the controlling is pure mechanical.

Any of the above require a permanent modification of the cart, and people without a special skill can't drive it easily.

Another idea is to install a sprocket onto the steering wheel, and use a motor to turn it via chain drive. Make a method of de-energizing the motor and anyone can steer it. Electronic controls are light and cheap. I like this idea the most so far.

For a motor, look for a large servo motor. A servo motor is a special motor that provides feedback for its exact position. Using some basic electronics you can command it to, say, 7.2 degrees right and it'll go and stay there. The controls can take several forms, so as he improves different control schemes can be considered, not just a lever at his left foot.

Thinking off topic a little, he might even be able to control this with his head - turn right to steer right, and so on. Does he have good control of his neck?

OK, enough speculating for now. Let us know about #1.
Oh yes, we also need to know a little about you: Your experience, skills, machining capabilities, and budget.

[cg285]

Originally Posted by Don Rotolo

OK, so do we find you a team in Orlando, a team in Va Beach, or both?

Also, before we start: We are a bunch of practical guys, some engineers, some not, and a LOT of High School kids, here on this forum. You and your son need to be the final deciders if something is safe or not.

OK, let's understand the problem: He has some use of his legs, but not his arms or hands. That means to me that he can use throttle and brake, but not steer. Is that right? yes, correct

Going on that assumption, if the right foot is go/stop, the left foot needs to be steering.

Problem #1: How does the left foot control steering. That is, does one use a gas pedal type control (press for right, pull for left) or a side-to-side lever? I would hesitate for a push/pull arrangement, since a big bump could cause an inadvertent turn. But, think about your son's capabilities and let us know what you think. he is capable of most anything

Problem #2: OK, we have some kind of input, how to we physically move the steering wheel?

A linear actuator directly on the steering box sounds nice, but as you said most are really not suited for that - but check McMaster.com and Google for other styles that might be workable.

Pneumatics are right out, since they can't hold a given position (Air compresses)

Hydraulics are fine, but need a pump for pressure and some plumbing. You don't need a lot of power (= thin cylinder, maybe 1" or so), but the controlling is pure mechanical.

Any of the above require a permanent modification of the cart, and people without a special skill can't drive it easily.

Another idea is to install a sprocket onto the steering wheel, and use a motor to turn it via chain drive. Make a method of de-energizing the motor and anyone can steer it. Electronic controls are light and cheap. I like this idea the most so far. this was my first idea but i think it would have to be a geared head motor

For a motor, look for a large servo motor. A servo motor is a special motor that provides feedback for its exact position. Using some basic electronics you can command it to, say, 7.2 degrees right and it'll go and stay there. The controls can take several forms, so as he improves different control schemes can be considered, not just a lever at his left foot.

Thinking off topic a little, he might even be able to control this with his head - turn right to steer right, and so on. Does he have good control of his neck?

OK, enough speculating for now. Let us know about #1.
Oh yes, we also need to know a little about you: Your experience, skills, machining capabilities, and budget.

i can deal w/anything mechanical inc fab & machine. i'm just back online from the weekend and am absorbing the posts. i'm going to investigate the tricycle thing. the boy might not like it but sounds intriguing to me (work on lower body while commuting). his idea for a golf cart is because he already has one. thanks for the ideas, cliff

[DonRotolo]

I agree, if there's a way to get him some aerobic exercise in the deal, it's good. But we don't want to tire him out just yet.

Instead of complex electric motors, sensors and and chains and stuff, maybe just a linkage between a foot plate for steering and the original steering shaft. Left foot steers, right foot gas/brake. Simple is usually best.

Let us know how we can help.

[cg285]

well the aerobic thing is out as i found out he has no sweat glands (only on his butt which didn't get burnt) and has to monitor temp always.

looked @ the cart this weekend. 3turns lock to lock, using a rack/pinion connected to a bell crank. not alot of effort to turn.
my thinking is a linear actuater connected to the bellcrank would be real easy but the duty cycle and the fact that it would not be easily converted back to manual operation is a concern
coming from an automotive background i thought about splitting the mast jacket, adding a sprockett to the strg shaft, sandwiched between 2 collars and a chain drive to a wiper motor or window motor. bushing the driven sprockett and securing with a removable pin or a gear dog. that way it's easy to change for normal steering.
fab a footpedal w/springs and stops to control range and effort. weld 2 pieces of bar stock forward and aft of center to operate a windlass sw (reversing sw)
other issues:
old style dimmer sw mounted on firewall (w/lighted indicator) for on/off.
makeup for/reverse arm, hanging down w/handle for leg control
lengthen the existing rail on driver side of seat and adding a safety net from rail to roof (driver unable to fasten seat belt, etc) enter from pass side
what do you think, too easy?

[Tom Line]

The wiper and window motors we use (denso) do not have the torque to steer the vehicle. In addition, they are not built for continuos cycle and at high torques will trip out their internal thermal breaker. They don't have the rotational speed you would need to gear them down far enough and still have responsive steering. They also aren't terribly robust - they strip their worm gear out fairly easily.

Perhaps you could use one of our inexpensive "cim" motors which are quite powerful, durable, and inexpensive, and run them through a reduction transmission. I'd think that a ratio of 48:1 or a bit higher would be a good mix of speed and torque.

You could do that with off-the-shelf transmissions here:
http://www.andymark.biz/am-0141.html (3 stacker boxes)

Or here:
http://banebots.com/pc/P80K-nnnn-0005/P80K-444-0005

I would run an auto-resetting 40 amp fuse through the banebots transmission. The cim has 103 oz-inches @ 40 amps. That's 0.536 lb/ft of torque, and through the transmission will be 34 ft/lbs. (Someone can check my math if they like). That's a safety factor of 2 against the rating of the banebots gearbox. You could drive the steering with 35 chain from mcmaster, and simply have a foot control that turns the current on and off, left and right.

[GarrettF2395]

Originally Posted by Don Rotolo

I agree, if there's a way to get him some aerobic exercise in the deal, it's good. But we don't want to tire him out just yet.

Instead of complex electric motors, sensors and and chains and stuff, maybe just a linkage between a foot plate for steering and the original steering shaft. Left foot steers, right foot gas/brake. Simple is usually best.

Let us know how we can help.

I completely agree with this. Simple and solid is absolutely better in this situation.

My suggestion would be to install a 2nd steering wheel at foot level, directly attach it via rubber belting (or chain) to the original drive shaft. BAM there you have it!
This allows the cart to still be steered by its original wheel as well.

Now if you want to get extra fancy with it, you could also attach the accelerator to the steering wheel. This will make the steering wheel act as the gas pedal.
(ie. When he pushes in on the steering wheel, it causes the cart to accelerate.)
This would allow him to use both feet for steering, instead of just his right or left and thus, makes it safer. <-just an idea

[EricH]

The problem you'd get with a second wheel is the lock-to-lock turning is 3 full turns. Most of the time, you'd only need a little bit of steering, but when making a tight turn, you can easily run into trouble. If that were done, I'd locate it off the drive shaft (structural addition may be needed) and link it 1:1 or maybe 1:1.5, then put a spinning flat knob on the additional wheel, equipped with a bicycle toe clip and most probably a heel jam of some form, to allow the driver to fully turn the wheel. Some buses have a small knob sticking up from the wheel; this would serve a similar function.

[GarrettF2395]

Originally Posted by EricH

The problem you'd get with a second wheel is the lock-to-lock turning is 3 full turns. Most of the time, you'd only need a little bit of steering, but when making a tight turn, you can easily run into trouble. If that were done, I'd locate it off the drive shaft (structural addition may be needed) and link it 1:1 or maybe 1:1.5, then put a spinning flat knob on the additional wheel, equipped with a bicycle toe clip and most probably a heel jam of some form, to allow the driver to fully turn the wheel. Some buses have a small knob sticking up from the wheel; this would serve a similar function.

Great idea! I had thought about using something like the wheel knob (also found on some tractors and semi-trucks). A device like this would help the user greatly!

Also, if my understanding of the lock-to-lock being 3 turns is correct, then couldn't you just make the "foot wheel" a smaller diameter then
the main wheel to decrease the number of rotations it takes to hit its left or right limit?

[cg285]

i'll look into a "cim" motor as i am not familiar with it. on the other hand we use a bosch wiper motor for trucks & rvs that has 38 # torque and is 100% duty cycle.

[PAR_WIG1350]

the Chiaphua Components Ltd. Industrial Motor (CIM):

From Andymark.biz

Performance specifications
Voltage: 12 volt DC
No load RPM: 5,310 (+/- 10%)
Free Current: 2.7 amps
Maximum Power: 337 Watts (at 2655 rpm, 172 oz-in, and 68 amps)
Stall Torque: 2.42 N-m, or 343.4 oz-in
Stall Current: 133 amps

[theaznevan]

wow everyone here has got great ideas, and i take no offense if you guys don't like my idea. how about a tank drive kind of system, two pedals, one on the left other on the right and each control its respectable side of the cart. (right controls right side wheels, vice versa). another parking brake kind of pedal can control forward/reverse drive. the problem i see here is this system is highly custom configuration and might cost big bucks. nevertheless its an idea! not very detail im afraid though haha. i wish the best of luck and recovery to you, your son and your family!

[548swimmer]

Originally Posted by theaznevan

wow everyone here has got great ideas, and i take no offense if you guys don't like my idea. how about a tank drive kind of system, two pedals, one on the left other on the right and each control its respectable side of the cart. (right controls right side wheels, vice versa). another parking brake kind of pedal can control forward/reverse drive. the problem i see here is this system is highly custom configuration and might cost big bucks. nevertheless its an idea! not very detail im afraid though haha. i wish the best of luck and recovery to you, your son and your family!

I applaud your input as such a new CD member, (welcome to CD by the way) though this is time for a teaching moment. That is a good idea however <lesson>previous posters have already come up with it and nixed it. Reading a thread in it's entirety as well as searching before you post will yeild much better forum usage for all!<\lesson>