Wheelchair lift concepts for Travel Trailer

[David Mast]

Hello all, i recently purchased a travel trailer, and i want to create a lift to get inside it.

a little background on me, i was in a motocross accident, broke my back and am now paralyzed. I currently work at a full fabrication shop as a mechanical drafter, we have the capabilities to make anything i can think of.

I have a few ideas in mind regarding the wheelchair lift, but wanted to see if any of you can come up or think of some other ideas.

here are the parameters I'm trying to work with:

- be able to lift 275lbs
- stop in place (electric motor capable of holding weight)
- ideally, id like to weld it to the frame of the traileri can post a few pictures of the lift system in my truck, which uses a 12v motor to turn a ACME rod, which in turn lifts a small seat i sit on. I believe this would be the best concept. hardest part would be finding the correct motor.

 

[berkeman]

Hello all, i recently purchased a travel trailer, and i want to create a lift to get inside it.

a little background on me, i was in a motocross accident, broke my back and am now paralyzed. I currently work at a full fabrication shop as a mechanical drafter, we have the capabilities to make anything i can think of.

I have a few ideas in mind regarding the wheelchair lift, but wanted to see if any of you can come up or think of some other ideas.

here are the parameters I'm trying to work with:

- be able to lift 275lbs
- stop in place (electric motor capable of holding weight)
- ideally, id like to weld it to the frame of the traileri can post a few pictures of the lift system in my truck, which uses a 12v motor to turn a ACME rod, which in turn lifts a small seat i sit on. I believe this would be the best concept. hardest part would be finding the correct motor.

Welcome to the PF, brother. Real sorry to hear about your MX injury -- rotten luck. How high was the break?

What have you found when you look at existing van lifts? Can you re-use any of their designs? I'm pretty sure they are welded into the vehicle frame as you plan to do. Can you post some pics of your travel trailer, and some van lifts (from Google Images or wherever) that are similar to what you want to do?

 

[berkeman]

How high is the landing in your travel trailer compared to a van? Does it have double doors already, or are you going to have to widen the door? Have you looked at Toy Haulers with the big rear door?

http://www.accessiblevans.com/images/products/common-handicap-van-rentals/full-size-wheelchair-van-rental.jpg

 

[Rx7man]

Have you considered hydraulic lifts? Small electric pump units are readily available. Are you looking to just lift yourself or yourself and a wheelchair?

 

[David Mast]

Hello all, sorry for the delayed response.. I have came up with a pretty good idea. And will post up a few pictures of the 3D model tomorrow. Basically, I designed a mount that will bolt to the trailer frame. That mount will support a vertical post (2x2 x.187w 6061sq tube). And bolted to that is a electric camper jack. Look up happijac 4800 jack on YouTube. It is basically a liner actuator capable of lifting up to 3000lbs +. I designed an aluminum frame that bolts and pivots on the base of the camper jack, that will stop at 90 degrees (parallel with the ground, and then will fold up 90 degrees so it's parallel with the trailer while in transport).

My issue is the camper jack is pretty slow... About .50" per 2 seconds. I would like to increase that to more like 2" a second if possible by re gearing the gearbox between the motor and the shaft. I do know some info on gear ratios, but the whole hp, ratio and what not has me a bit confused. Do you think the motor will be able to lift me faster with a lower gear ratio? (Remember the "stock" ratio/ motor was designed to lift 3000lbs. I only need it to lift a maximum of 300lbs)

Any thoughts on the re gearing of the motor?

 

[Rx7man]

If the stock motor can lift 3000 lbs before it stalls, you should be able to gear it up 10:1 and it should lift 300, and that would be 2.5inches per second (may be a little fast)...

Now it already has internal gearing I'm sure, it would be a matter of reducing the amount of reduction it has.. if it's multiple stage, perhaps if you can bypass one stage it would work.. If it has a 50:1 reduction on the lead screw, perhaps it's a 5:1 followed by a 10:1 and you can bypass the 5:1 stage and you'd be set.

 

[David Mast]

If the stock motor can lift 3000 lbs before it stalls, you should be able to gear it up 10:1 and it should lift 300, and that would be 2.5inches per second (may be a little fast)...

Now it already has internal gearing I'm sure, it would be a matter of reducing the amount of reduction it has.. if it's multiple stage, perhaps if you can bypass one stage it would work.. If it has a 50:1 reduction on the lead screw, perhaps it's a 5:1 followed by a 10:1 and you can bypass the 5:1 stage and you'd be set.

I will take the cover and take some photos of the inside of the gear housing later today. I will also count the teeth of each gear so we can determine the gear ratio, and go from there

 

[David Mast]

Here is the lift concept I have come up with

 

[David Mast]

View from a different angle. I will post pics of gearbox in a bit.

 

[David Mast]

ok, so here are the pictures of the gearbox. and i counted the teeth on all gears and drew a representation on a sticky note. i hope you all can make it out clearly. and help me figure out the ratio?

 

[berkeman]

Is there a way to make it a 2-sided lift? The one-sided lift looks real unbalanced...

 

[David Mast]

as far as simplicity goes, no. the issue is with the door opening on the other side. if i went with the van style above, i would have to create a whole new trailer door to accommodate the width.

i may add an additional support that can slide up and down in a guide system to keep the camper leg straight (vertically) if the one sided load (weight on platform) hints at bending the tube to the left direction, which seems like a possibility considering the load (300lbs) will be all on the right.

 

[Rx7man]

It may require a second gearbox to be a 'donor' for gears, as well as some lathe work, but if you could take the 72 tooth and swap it around with the 32 tooth, that would get you pretty close to your goals

32:72 = 2.25:1
If swapped around the difference is
2.25*2.25 or 5:1... or 5 times faster than it currently is.. It should lift about 1 inch per second under load.. not blazingly fast, but much better than 1/4 IPS (which might be under no load, depending on the specs).

If you could find a motor a higher speed rating, that may be another way to go about it, it could afford to have as much as 10 times less torque (Maybe 6-8x to be safe) and still get the job done

 

[Ben123]

Can you ditch all the gears and machine the shaft for sprockets and just run a chain under the cover instead?

 

[Rx7man]

Can you ditch all the gears and machine the shaft for sprockets and just run a chain under the cover instead?

It would be really hard to get a sufficient gear reduction with a single stage chain.. about the best reduction ratio you can get with sprockets that would fit in the cover looks to be about 5:1 (10:50), tensioning may be a bit tricky too..

 

[Ben123]

Yes, good point. I think that changing the gear ratio might be more trouble than its worth... Would a different actuator be feasible? Or what about pulling it up with a cable?
Harbor freight has a 2500lb winch, that will pull 8.3FPM at 1000 lbs. That would be easy to mount on the top of the tube and run the cable down through. Has a wireless remote too!

 

[Rx7man]

I really don't like cables.. they love snagging and dangling and tangling.. that's just me though. I would find a way to do it hydraulically, where the cylinder is sized so that it can handle the side load as well.. another option would be to use a parallelogram style lift that attaches under the trailer...

Since he's already got the screw type lift, I'd give that a shot first.. and I think swapping the two gears I mentioned earlier would be the easiest way to keep everything meshing and looking pretty... The stacked gears may be two separate gears pressed on to a common hub.. if that's the case it would make it a lot easier to do, though it would still likely require a lathe.. it's worth looking into though