Homemade tracked wheelchair project

[undy]

The Industrial Arts kids have been great. They took some online class for a program called Solidworks and all three aced the certification test.

Here's a picture of early hub and sprocket prototypes:

The hubs were 3d printed. The sprockets were CNC router cut.

The finals are being machined as we speak. We ordered 5/8" id hubs from McMaster, and hogged them out to 7m. But the keyway is 6m, very wide for such a small shaft. The broaches available wouldn't fit into the hub, so they're being burned out.

Hopefully this is all done asap, and I'll have them in hand.

 

[undy]

Please remember that this is a first attempt. It may well fail. So far, the expenses have been under $320, so if it does fail, I try again.

And yes, I know the welding is atrocious. It was a free MIG I was trying to get working. It was worth what I paid for it. I am thoroughly embarrassed.

Here's a closeup of the track adjuster. Two square tubes slide within each other to maintain alignment, the threaded rod tightens it. It seemed to be able to achieve pretty good tension on the tracks, using the prototype sprockets.

 

[undy]

Here's a shot of one wheelchair motor mounted. When one was hung upside down without the mounting bolts tight, it leaked a small amount of lube. The bolt threads showed some sort of thread sealant on them.

Can you guys tell me what these should contain, how to fill them, and any other advice I need? Obviously, they were oriented differently on the original chair, but since they don't leak when the bolts are tight, I'm presuming they'll work fine like this.

In this photo, the track is fully loosened, and the sprocket is not on the drive shaft.

 

[undy]

The big question was, do these wheelchair motors have enough oomph to drive the tracks???

Partial Success Today!​

I got one sprocket and modified hub back and installed. The track moved, but with lots of jarring and jumping. I ended up rounding off the teeth on the sprocket some and playing with track tension, but it's running pretty smoothly now.

This morning I dropped it back onto the floor and gave it a try. With only one track driven and attached to batteries by an umbilical wire, it only spun in a circle. It moves, and on concrete at that, but not yet fully loaded.

The second spindle should be finished soon, hopefully today, and I can give it a test drive. If all goes well, I can proceed further on the seat, etc.

I am cautiously optimistic.

 

[undy]

Today I rode around my shop on the tracked wheelchair. It climbed over a 4x4, and is capable of spinning in a circle fully loaded and on concrete. Initial impression is very good. Still needs a seat though.

It will not, however, counterrotate, at least not yet. I expect this may change after the tracks get spun around a few thousand times and get somewhat softer, as well as on dirt instead of concrete. The reverse function seems to have less torque than does the forward.

More testing to follow...

 

[it's all about downhill]

Some one who knows may tell you different, but I like Lucas heavy duty oil stabilizer in gear boxes. I run it straight in my mower (8' flail behind 50 HP tractor) drive box. I haven't had to rebuild it since using it.

And play with that welder some more. Push vs pull, I'm thinking slower wire feed. The magic will come. Big difference for me is cleaning the lens pack and a NEW plastic cover...enlightening. YMMV

Those 3D copiers are so amazing. It's so surprising that the materials can be tough enough to actually be useful for anything other than a model.

 

[undy]

Good idea about the Lucas. I've got a bottle on my bench right now, as a matter of fact. Thanks.

That welder!! I got the damn thing for free, and it's worth every cent I paid. I just replaced the whip liner, but the feed is still just too sporadic. It's also a limited duty welder to start. Plus it's old metal and different thicknesses. Mind you, I'm making no claims as to my abilities either!! All my training came in high school, forty years ago. But so far, form follows function, and it hasn't fallen apart. (Yet.)

Working with the local Industrial Arts "Whiz Kids" and watching them make those prototypes has been absolutely thrilling. It's all new technology to me. I did try a 3d printed hub, but the motor just ripped the guts out of it. The final version was steel, with a plastic sprocket.

Today I'm going to see how far I can drive the thing around the yard before the batteries slow down.

 

[undy]

The project continues. Big changes to come.

I rounded off the sharper corners on the sprockets and got the tracks moving more smoothly. Using two good batteries out of my snow cat, the chair counterrotates well on concrete and climbs a 4x4 easily now. But. They are automotive batteries, and only worked well for about 3 minutes. It also can't be good for the batteries. I tried some deep cycle Optimas, but they don't seem to be good anymore and won't hold 12 v.

So my concerns about the robustness of this system continued. After all, this is only a first prototype, and it may or may not succeed.

Then I found a C/L ad for a "bariatric" wheelchair, a Wheelchairs of Kansas Overland model, designed for a 700# guy, with good batteries for $650 (I figured the batteries were worth half of that). I have now run it over a mile off-road on some pretty good inclines both front - back and sideways, without running the batteries down too far. It's possible that this chair could get down to the beach as is, but the track will be much smoother over rough ground than the tires.

I also tested these good batteries on the old track chair, and this seems to confirm that the original drive train is insufficient. I thought about just mounting the heavier drive train to the current tracked chair, but rather than cut up this W.O.K. chair, I am now going to fit tracks to this frame. This way, if things go badly, I can always reassemble the W.O.K. chair again and perhaps resell it.

New sprockets have been designed to replace the rear wheels, and will require a 5/8" spacer to allow the tracks to clear the belt-drive system of the chair. I'm hopeful to have these parts yet this week. They are 5/8 the size of the original drive tires. I estimate that this reduction will provide ample torque to drive the tracks, and this will also give enough distance to get Danny to the 1/4 mi. to the beach and back (based on my 1 mi. + testing).

I just ordered the steel for rebuilding the track systems. In order to provide clearance for the larger drive sprockets, I'll be slinging the frame below the boggie wheels (first model ran above). I'm also going to drop the center boggie about 1/4" below the #2 & #4 boggies to hopefully make it easier to counterrotate yet still feel stable. Then I plan to add a smaller, and more importantly, lighter seat (the old one is about 50#).

 

[MrLiberty]

It sounds like you might have to go with a four battery system to give you any distance. The motors are going to be pulling more power for the tracks lessening the distance you can travel.

 

[undy]

Thought about that. It was even suggested that three 8v golf cart batteries would work too.

I'm hoping that by decreasing the sprocket size by 37%, and decreasing the load, (Danny only weighs about 165, plus I'll get rid of some weight with a lighter seat), the motors should not be seeing that much of an increase in load, if any.

But yeah, so long as the machine has sufficient power for the job, more batteries would let it travel further.

 

[MrLiberty]

I have been toying with the idea of trying to mount a solar panel on a chair that would keep charging the batteries while you use it, outside of course.

I have it figured out in my head, but haven't put it down on paper yet.

 

[turbinator62]

Thanks, but nope. That wasn't it. The one I'm remembering had details on how to actually lay out a sprocket, based on the pitch of the track, IIRC. Maybe it was the other way around - how to space grousers based on pitch of the sprocket.

At any rate, I have tracks with a given pitch, and I need to lay out a sprocket somewhere around 10" diameter to fit those tracks.

This may be the post you are referring to.

http://www.forumsforums.com/3_9/showthread.php?t=63147&page=2

Start at post #33. Read it and if you still have questions post a reply and I will try to answer them.

 

[300 H and H]

And play with that welder some more. Push vs pull, I'm thinking slower wire feed. The magic will come. Big difference for me is cleaning the lens pack and a NEW plastic cover...enlightening. .

Wire brush the area to be welded till it is like new looking...

You always "push" away from you the mig gun when welding. Have some one adjust the wire speed while you are laying a practice bead, and adjust this till the welding sounds like bacon frying in a pan.. You should never feel the wire kicking back on the gun. If you do the wire speed is to fast, or your heat range is too low..

Really wish we had 30 minutes of shop time together Paul.. We could have a good time and figure your welder out.

Great project, look forward to more.

Regards, Kirk

 

[undy]

Turbinator,

Thanks. I'm pretty sure we've gotten the sprockets laid out accurately. The first version was only 6" diameter, and it didn't skip at all and worked well in both directions. This newer sprocket will be 10" diameter, so with the straighter arc will engage an extra tooth. I expect it will work even better than the first one.

Kirk,

Ditto the wish to work together. You're pretty much describing my efforts, pushing the lead and working the speed to get it to work at the voltage I want. BUT, I'm afraid I'm chasing after a whole bunch of equipment failures.

The wire drive seems to often slip and not feed the wire, and I've tried two different brands of wire (one Harbor Trash and one Hobart), replaced the whip wire conduit (plastic tube-like thing), etc. The wire drive is not slipping on it's drive shaft, but rather just doesn't seem to grip the wire well enough. I fiddle with the speed, seem to get a nice fried egg sizzle, and then nothing. Pisses me off, because it used to do a decent job, but at some point it just isn't worth the aggravation!! The last exhaust repair I did, I finished with my arc welder (!).

I've been known to do impulsive things. The last push mower I bought new from Menards (MTD. Shoulda known better.) began to fall apart the very first time I used it. I rewelded the deck several times. Then the recoil would fail to recoil. So I'd disassemble it and make it work. This continued through that summer. The next spring the recoil failed again. I fixed it, and it failed again. You should understand that to fix this recoil, the top plastic cover and gas tank had to be removed. You might see where this is going...

The recoil failed again. I ripped the plastic cover off (no tools!), emptied the gas tank onto the mower, and lit her up. Then I went to the house for the shotgun. I'm still finding pieces of that mower over by the barn. But it'll never mess with anyone ever again.

Maybe this mig welder would be better off filled with concrete and used for a boat anchor?

 

[JimVT]

my hose that has the gas and wire got squashed on my small welder. after that I had to keep it pretty much straight or it slipped feeding the wire.
are you using gas?
the Hobart welder web page has instructions that help me some. I was never able to do a good job until I bought a much larger one.

 

[undy]

Jim,

I replaced the plastic "hose" that the wire feeds through, but still have problems, even when the whip is pretty much straight. Yes, I do use gas.

I'll look up that Hobart page and see if I've missed anything.

I too am considering a larger mig, as they seem to be less problematic. I used to have access to a gigantic one with an outboard wire feed, and it was a whole new ballgame.

 

[MNoutdoors RIP]

Undy,

Three things to check.

That the wire matches the groove in the feed wheel like .035 or .045
Some have both based on which way it's installed

Second

After a lot of used the drive rollers can get worn in the groove not pushing like they should also check the tension on feed wheel


Third

The gun liners get dirty speacialy if you not using a felt wire wiper in front of your drive wheel if your gun has a liner ( mine are removable they look like a spiral wound outside choke cable shield ) clean them with brake cleaner a the accumulated dirt and grit gets in them.

 

[undy]

Brad,

Thanks.

It does have two grooves. I'll have to check for a size marking on it and make sure it's set to the right size. Do the grooved feed wheels wear out?

The tension wheel seems to be working okay. It's just a bearing with a spring to provide pressure.

You're bumping my obviously failing memory. The liner I replaced was in fact a spiral shield (Not a plastic hose as I previously wrote. That was for the gas. D'oh!) I have been using the felt wiper. Even though the line is pretty new, I should probably clean it to be sure.

Looks like I have a bit more checking to do, before I bust out the demolition equipment.

Thanks for the tips.

Paul

ps I may have to start another thread on welder troubleshooting, the way this one's going!

 

[undy]

Okay, still no joy with the MIG. But that hasn't stopped progress.

Yesterday I drove the new tracked version over 1/2 mile. It can climb a 4x4 and counterrotate. I still have to reconfigure the seat to cut some weight, but it's much closer to working.

A question for those of you who might be familiar with power chairs. The drive motors got quite warm while driving. Not quite too hot to handle, but close. I'm sure this isn't ideal, and leads to shorter operating time. But how hot's too hot?

My plan is to strip off the track assembly and reinstall the wheel/tires and test run it. If the motors get similarly hot just when I run it in the stock configuration, then I think I can assume that it's just normal conditions. If they stay cool with the tires, then I can conclude that the tracks are drawing too much power in use.

Anybody here know how hot wheelchair motors can get safely?

 

[it's all about downhill]

One thing no one has mentioned (that I noticed) (but you probably have done) is the tip that the wire comes out of. Those will wear out and stop making good contact. Probably need to replace it about every roll of wire. Too obvious, but the ground must have great contact. If the clamp is hot, there is resistance somewhere.

I don't know the temperature answer. Smoke is a bad thing. not burning skin when touched is good.

 

[MrLiberty]

Okay, still no joy with the MIG. But that hasn't stopped progress.

Yesterday I drove the new tracked version over 1/2 mile. It can climb a 4x4 and counterrotate. I still have to reconfigure the seat to cut some weight, but it's much closer to working.

A question for those of you who might be familiar with power chairs. The drive motors got quite warm while driving. Not quite too hot to handle, but close. I'm sure this isn't ideal, and leads to shorter operating time. But how hot's too hot?

My plan is to strip off the track assembly and reinstall the wheel/tires and test run it. If the motors get similarly hot just when I run it in the stock configuration, then I think I can assume that it's just normal conditions. If they stay cool with the tires, then I can conclude that the tracks are drawing too much power in use.

Anybody here know how hot wheelchair motors can get safely?

The motors on a regular powerchair will get warm, not hot, and I suspect that because you have added more stress to the motors by adding tracks that you are going to look at a shorter lifespan for the motors.

 

[undy]

I think it's about time to update and wrap-up this thread for 2015.

I tested the wheelchair on tires, and the motors do not get very warm at all, even under heavy extended driving.

I got an opportunity to inspect and drive an Action Trackchair that a local guy owns. In a short test run, my chair compares very well. Mine is perhaps a slight bit faster, but otherwise just as capable, except that the Action chair has a tilt seat to aid in steep climbs. However, those tracks are WAY less thick than what I'm using. On a positive note, the motors are very similar to what I have. The Action chair has a 90 degree gear reduction drive output and mine uses a chevron cogged belt with sprockets for reduction.

So, with that info in mind, I set off for the island with Danny.

First time out, the chair had been sitting for several days, so the charge was not topped off. We lost the first green LED about 1/2 way to the beach, but I figured we'd best continue, just in case the rest of the weekend was rainy. By the time we started back uphill from the beach, we lost the second green LED. It was a long push back uphill through the sand...

The second day out went better. We got down to the beach and a few hundred yards before the first LED died. But I still ended up needing to help push it back part way.

Conclusion: The power-buggy tracks are too substantial and offer too much rolling resistance to work for a wheelchair. I will spend the winter trying to source proper tracks. FWIW, the commercial tracks are more like thin conveyor belt material, with straight rubber "grousers". If I can find or make some, I'm convinced this chair will work.

Anyone here know where I can find the thinner tracks? (They are still 7" wide, but just thinner material.)

In the meantime, the thicker tracks will find a new home mounted onto the rear of a lawn mower, with new tin bodywork to look like a halftrack. I figure that way I can putt-putt around at the Iola Old Military Vehicle show in style!

 

[300 H and H]

Paul I have an MTD (Troy Built)snow blower that has some small tracks on it. May not be long enough, but the width might be ok..

How long do you need?

Regards, Kirk

 

[undy]

Hi Kirk,

I've thought about those, and they are somewhat similar. But I need them to be bigger.

The current tracks are 7" wide by 87" long. So the track assemblies on the chair are about 36" long.

As a last resort, I wondered about stringing several snowblower tracks together. I'd rather get the full length tracks if possible.

Thanks,
Paul

 

[DAVENET]

How long were the tracks on the Action Trackchair? You have already done all of the hard work getting everything set up & working. How much would a set of replacement tracks from Trackchair be and would it work with your sprocket configuration?

 

[undy]

Hi Dave,

I "lifted" the size from Action's website, and sourced similar sized tracks. They list them as 6-1/2" x 90". That's also the type of chair I inspected.

The current tracks have center holes which the sprocket teeth fit into. Because the Action tracks are less thick, they are made different. They have small rubber tabs, sort of like an inner grouser. The tabs keep their track centered between the bogey wheels and their sprocket is more like a waterwheel that grabs the rubber tabs.

If/when I get the correct tracks, I'll have to redesign the sprockets.

Paul