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$ 5000 Tug

Plus 1

Plus 1 Scott
Finish the tailwheel airplane?



Or of course, copy Alex, who has some great ideas here. I originally wanted the twist grip throttle, but could not locate one with a potentiometer spring loaded to center, the operating scheme for the fancy Sabertooth controller. Alex sidestepped the issue with the forward-reverse switch and a much less pricy controller. The differential in the axle allows turning without resistance, an overlooked detail. For example, the cheap tugs built with the snowblower gearboxes are indeed resistant to a sharp turn when loaded. Flip side is that one wheel may spin, but Alex has since run it in the snow and it does not seem to be a problem. Steering via independent motors doesn't have that issue, but brings us back to the human interface (currently a joystick) and controller choice.
 
I hesitated to post this with all the impressive engineering done by others. Not being nearly as talented, I took a much simpler approach. SNIP

Keith - the most elegant engineering is the simplest! I tip my hat to your solution. I also like the idea of the operator being the ballast, both for practical traction purposes and for sport. Do you have a sense as to how much the thing weighs?
 
Keith - the most elegant engineering is the simplest! I tip my hat to your solution. I also like the idea of the operator being the ballast, both for practical traction purposes and for sport. Do you have a sense as to how much the thing weighs?

Alex - the chassis is 100 lbs, the batteries (2) are 24 lbs each, and the seat is 37 lbs.
 
Finished this AM. Works fine on the shop floor. Left-Right function is perhaps a bit too sensitive, but I'll get it to the hangar this weekend and see if it's a practical concern.

Yeah, grand overkill, but hey...
.

Dan....I'm impressed again! Is there anything you can not do?

Scott...I second Dan's advice: Finish the RV-8! You'll love it.
 
Alex - the chassis is 100 lbs, the batteries (2) are 24 lbs each, and the seat is 37 lbs.

Alex is right, it's a good solution for a towbar application where the system doesn't lift the wheel off the ground. Offhand I don't know how much weight the typical nosewheel would add to the tow chassis when lifted. The tail wheel on my -8 is about 105 lbs when lifted off the floor. The new dragger is probably 75 lbs with two PC-985's. The combined mass appears to be enough to negate wheelspin.

So far I'm tickled with it. Plenty of power, silent, easy to couple, and instantly ready with the flip of a switch.

BTW, I traded emails with Dimension Engineering, the folks who make the motor controller. I can modify the response to left-right joystick input with a bit of re-programming. I'll let you know how that works out.

No one asked about the pair of contactors below the motors. They decouple the motors from the controller when the master switch is off. PM motors are generators when spun, as they would be when the unit is pushed around the hangar in an unpowered state. With one motor wire open, they spin freely, and do not energize the controller, which may be damaged with the batteries disconnected.

Balance worked out pretty well. 50 lbs of batteries obviously give it an aft CG when not hooked on the tail wheel, but when hooked and tail lifted, it only takes a few lbs of downward pressure. The torque reaction is larger than the static.
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The nosewheel weight on my plane is around 320lbs, maybe 30-40lbs higher with full fuel and no pilot. The tug I made might put an additional 40 lbs on the drive wheels. So, Keith, if you could put the operator on your rig you'd be similar (although I suppose the 14 has more nosewheel weight than the 6). Would probably only be needed in slippery winter type conditions.
 
The nosewheel weight on my plane is around 320lbs, maybe 30-40lbs higher with full fuel and no pilot. The tug I made might put an additional 40 lbs on the drive wheels. So, Keith, if you could put the operator on your rig you'd be similar...

Alex and I kicked around a few ideas early on. My original concept was a rider, first seated, then a stand-up (concept sketch below), which moved rider mass forward after Alex suggested the sit-down would need wheelie bars

It would have had a single upright post, hand holds to be determined, with a joystick. The tailwheel hooks would have been on a pivot, and when the operator stepped on a round pedal, it would have picked up the tail. A simple latch mechanism with a release on the handlebar would hold it up.

The goal was to swoop in, pick up the tail, and go. The concept could perhaps be changed to a nose wheel capture, and adapted to a chair chassis. Or not; the 350 lb lift may be too much.

Note platform carefully sized for 14's ;)
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Universal tug

It seems creating a universal tug that will scoop up and securely hold a nose-wheel with a tight, low fairing is probably one of the most challenging tasks. Using the existing tow bar is the easiest solution, but it has drawbacks.

I've got a bid in on a wheelchair with some spare parts - hopefully I can steal your ideas and create something that will help me move "the beast" that's between my RV-8 and the ramp in my shared hangar.
 
Mickey - steal away. Your point about the nosewheel needing to be securely attached using the tow bar points if important. The nosewheel can't simply be lifted, even if it were chocked on the lift platform. It also needs to be prevented from castering as one main hits more resistance than the other.
 
Mickey - steal away. Your point about the nosewheel needing to be securely attached using the tow bar points if important. The nosewheel can't simply be lifted, even if it were chocked on the lift platform. It also needs to be prevented from castering as one main hits more resistance than the other.
Thanks - I was thinking maybe something like a vise clamping on the rubber part of the tire would provide enough grip?
 
Thanks - I was thinking maybe something like a vise clamping on the rubber part of the tire would provide enough grip?

That might work if you get get a big enough bite. It would depend on how likely a main is to hit resistance such as a small step in the concrete, a chunk of ice, etc. When pushing a trike backwards, one feels surprisingly strong lateral tugs at the handle of a four foot tow bar as one wheel hits resistance.
 
My tug

Heres a photo of my tug, only had to buy the mobility motors, everything else was laying around or need to be modified. Need to put weight on the handle to get traction to move RV7. Modest amount of leaning to move over door tracks and no grade on ramp.

Keith Rhea
RV7
2021 donation
 

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I hesitated to post this with all the impressive engineering done by others. Not being nearly as talented, I took a much simpler approach. Since wheel chair motors are a favorite drive mechanism, I started with a used wheel chair, this particular model - a Jazzy Select 6

I can step on the step applying 150 pounds of ballast that gets the tug moving. An improvement would be built in ballast.

I have found this setup easily accomplishes my goal of a tug for my hangar ramp (gentle - about 2 degrees), but is trickier (non-intuitive) for close maneuvering - like turning the plane around and backing it into place - it will do it, but requires some spinning of the tug to swing the handle, and its just easier to disconnect for the final parking.

A great solution! For it to work for me up here, would need knobby tires & maybe 200+ lbs of ballast.
2 weeks ago I had a tough time getting the 6A back into the hangar, 1.5" of snow over glare ice on a slight upgrade. Nearly took out 2 teeth on the tow bar. Ended up getting the tractor out & positioned it's snow blade center on the tow bar & nudged it straight back into the hangar. I was too he/man proud to call some buddies for help...
 
Minor note.

I originally wired an LED light in parallel with the master switch, to indicate the power was ON. First weekend, I managed to walk away from it and leave the power on, despite the light. Luckily I found it an hour later, so no issue, but it did serve as a warning. It would be an unhappy thing to return a week later and find a pair of totally dead PC925's, as sometimes total discharge kills them forever...and they ain't cheap.

Found these on Amazon...a larger flashing light AND a beep-beep-beep aural warning. Foolproof for sure. Well, at least until Ms. Patti builds a better fool.

https://www.amazon.com/DIGITEN-Flas...a892e&pd_rd_wg=TkJXG&pd_rd_i=B017YL31OY&psc=1
 
Found these on Amazon...a larger flashing light AND a beep-beep-beep aural warning. Foolproof for sure. Well, at least until Ms. Patti builds a better fool.

My AeroTow tug had both a continuous-on red lamp and a Sonalert beeper to signal power was turned on. The company owner / product designer found a better solution to these annoyances. In the next iteration of motor controller a 10-minute "idle" timer was incorporated. The tug simply shuts down after 10 minutes of inactivity. The main power switch must be moved to the "off" position and then back to the "on" position before the tug will operate again after a time-out event.

I really like this new functionality as I hated the beeper. And no, I won't disclose how many times the 10 minute timer has saved my batteries! :D
 
My AeroTow tug had both a continuous-on red lamp and a Sonalert beeper to signal power was turned on. The company owner / product designer found a better solution to these annoyances. In the next iteration of motor controller a 10-minute "idle" timer was incorporated. The tug simply shuts down after 10 minutes of inactivity. The main power switch must be moved to the "off" position and then back to the "on" position before the tug will operate again after a time-out event.

I really like this new functionality as I hated the beeper. And no, I won't disclose how many times the 10 minute timer has saved my batteries! :D

I like this idea. I have a small white led light (might be for cargo beds, not sure) that I plan to hook to mine as a "I'm on" indicator. I like the timer idea better. A simple latching timer relay is all it would take - push a momentary contact button to engage, use the tug, and forget it. Nothing is gonna happen until warmer weather though...
 
Basically free

I found a Jazzy mobility chair down on the curb with flat tires and ripped seat, just waiting for a scrap guy to scoop it up. I knocked on the front door of the house and got clearance to take it away.

A few hours in the shop with some scrap metals and welder and came up with this. Roll it up to the tire, winch up, lever the tire off the ground, and go. All the weight is on the tug so it has excellent traction. The chair electronics work perfect and it’s got plenty of power. I also left it on by accident and it must have a battery saver because the lights were still on and it still worked after a week.
 

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I found a Jazzy mobility chair down on the curb with flat tires and ripped seat, just waiting for a scrap guy to scoop it up. I knocked on the front door of the house and got clearance to take it away.

A few hours in the shop with some scrap metals and welder and came up with this. Roll it up to the tire, winch up, lever the tire off the ground, and go. All the weight is on the tug so it has excellent traction. The chair electronics work perfect and it’s got plenty of power. I also left it on by accident and it must have a battery saver because the lights were still on and it still worked after a week.

Amazing. I envy you guys..
 
...A few hours in the shop with some scrap metals and welder and came up with this. Roll it up to the tire, winch up, lever the tire off the ground, and go. All the weight is on the tug so it has excellent traction. The chair electronics work perfect and it’s got plenty of power. I also left it on by accident and it must have a battery saver because the lights were still on and it still worked after a week.
Anthony, I might be wrong, but there looks like quite a bit more going on here than meets the eye. Really nice. The lever mechanism appears both complex and simple - I'm guessing quite a bit of thought went into that part for sure.
 
Anthony, I might be wrong, but there looks like quite a bit more going on here than meets the eye. Really nice. The lever mechanism appears both complex and simple - I'm guessing quite a bit of thought went into that part for sure.

Thanks Mickey. It is complex but simple as you say. I built pieces as I went and it all came together nicely. I sure didn’t have the big picture planned out. I’ll say I was pretty proud of myself when it was done.
 
Previously I wrote:

...I traded emails with Dimension Engineering, the folks who make the motor controller. I can modify the response to left-right joystick input with a bit of re-programming. I'll let you know how that works out.

Short version...motor response to left-right input was far too abrupt, but reprogramming fixed it.

The Sabertooth controller is a fancy piece intended for robots. Tech details are above my pay grade, but changing motor response to the joystick input was a matter of downloading a program (DEScribe), connecting a laptop via a USB to TTL converter, resetting some DIP switches, then uploading a new set of instructions. See the screenshot below. Forward/reverse is the standard exponential response curve, but the left/right response was reset to be a straight line with full stick deflection equal to only 10% of available motor speed. Seems to be just right.

Oh yeah, one other detail...I added a tailwheel. Now it can't bump its butt on the hangar tracks.
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Picked up a used wheelchair that works fine. Stripped off the unneeded stuff to just see if it has the power to move the beast that's between me and the taxiway.

I used Keith's idea to capture the towbar handle.

It will take some time to learn to maneuver this thing, and I had to put the towbar capture very low, or it wanted to tip over, even with a bunch battery weight. My back is already happier!

IMG_3756.jpg

One question - the motors say that they are 24v with 3.3 amps - this seems like very low power - is this standard for wheelchair motors? Mine feels a bit lethargic, but perhaps because I'm currently testing with some very tiny batteries.
 
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Drill Tug

Hi Dan

Love your drill tug, trying to build one myself. Were did you get the drive shaft/gearbox to drive the wheels. I've searched google to no end.

Cheers, Jurgen
 
R/C controller

Question for you guys- How do you get an R/C controller to work with a Jazzy mobility controller?
 
simplicity at its best

Lightweight, cheap, and functional to move my RV-10 in and out of the hangar.
No programming or configuring or futzing with software. Toggle fore and aft and a rocker switch to activate the fork.
Notice the linear actuator controlling the fork, no bending over to hook up the front wheel.
Yeah, you have to build it.

IMG_7651.jpg

IMG-7637.jpg
 
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