Main gear drawbar

[Stinger]

Tossing around some ideas for a way to tow/pull my MX7 with the oleo gear. One of them involves making a drawbar connecting the main gear to a hitch for a lawn tractor. Then pushing the airplane into the hangar tail first for space constraints. My question is would there be any airplane maneuverability with that set up? Thinking it would be mostly limited to straight forward or back...

Might be easier to attach to the tailwheel, get the plane into the hangar from the soft grass and steel door tracks, then maneuver by hand the last fifteen feet.

I've got an unused Ryobi string trimmer I'm trying to figure out a way to use. Needs a gear reduction to connect to the drive shaft I'm almost positive, but coming up empty on where to get something like that.

It's been a few years since the last tow bar discussion, anything new?

[andy]

You'd need a really long tow bar to push from the front of the airplane - maybe 30 feet. You'd have to position the prop horizontally to be clear of the tow bar and make sure it's low enough to avoid the transponder antenna. Turning range would be limited to avoid hitting the oleos if the tow bar is attached to the axle bolts on a Scott tail wheel.

I assume that you don't want to spend much money on something like the Best Tugs A3 that I have: https://www.besttugs.com/a-3-info. A few owners have fabricated their own or bought less expensive gas power tugs. Minimax tugs look interesting on the lower cost end of the drill-powered line:
https://www.youtube.com/watch?v=GlwAW4-I3gg

[Stinger]

Definitely looking to go cheap on it haha

30 feet seems like at least double what is needed. Main wheels to front of prop looks to be maybe 7 feet just looking at a Maule picture. Then an extra 4 feet for clearance and I'm at at least under 15 feet.

I currently use a taildragger dragger which is great for pavement, not so much for grass fields. If I'm going to make my own powered version it'll be a similar cradle to hold the tailwheel (may even just use the bottom half of what I have). Then a handle to lift the tail a bit and get the weight onto the tow bar wheels and locking in place. Just need to figure out the gearing reduction and fabrication.

[Andy Young]

I have used a drawbar such as you describe for moving Otters from the front, with the bar attached to the main gear. I found it strange, as I was used to towing from the tailwheel, but that’s how this particular operator did it, so….
I got used to it, and it turned out to be an easy and accurate way to stuff the airplanes tail-first into the back corners of the hangar. Pushing from the front meant nothing in the way at the back. No tow vehicle to move out of the way to get the last several feet into the corner.

It was just two pieces of steel tube, able to hinge at the hitch end, with shackles at the other end to attach to a handy holes that happen to be there already on Otter gear legs. Have to work out a different attachment method for the Maule.

[onfinal]

Hi Stinger,
I guess you are taking about an 'A frame'. Our Ground Ops use such an 'A frame' to move a couple of Daks (C-47) in and out of our hangars. They push them in tail first, steering with the tail wheel and tractor hitch. The guys make it look easy but I'm sure it's a challenge, which with practice can be overcome.
Engineering fabricated the frame, it's tubular steel and chunky, although very rudimentary in design, with two retractable support wheels. Rather big and hard to tidy away. Andy's hinge sounds like a good aid for storage.

Not sure how the compression of a Maule's oleo struts and hence 'rocking' motion might effect mobility. A tire might 'dig in' as its strut compresses when turning. Not an issue on the C-47. As Andy highlighted, attaching to the Maule main wheel structure might be the first issue to resolve. Is there a Maule Mod ?

[Kirk]

I wonder how much side load a 2 bar setup would put on the main gear? It would try to spread the gear pushing back and pinch the gear in while pulling…. An ‘A’ frame would not have that problem.

Kirk

[Andy Young]

I wonder how much side load a 2 bar setup would put on the main gear? It would try to spread the gear pushing back and pinch the gear in while pulling…. An ‘A’ frame would not have that problem.

Kirk

I never had any problems along those lines with the Otters, but the bars were pretty long; long enough that the angle at the hitch was probably not more than 30°. That angle could make a big difference in how much of an issue this is, if any.

[Flyhound]

I'm still fond of the electric "hand truck" I built out of square steel tube, a bit of round tube, some electric scooter parts (1kW motor, controller, 48 volt LI battery pack, throttle, pneumatic tires, wheels and gears). It gets over the tracks for my sliding hangar door and it has plenty of power for the slight uphill tow into the hangar. My original tow bar was a Tail Picker 1, but the solid tires took quite a hit each time they rolled over the steel track for the hangar door and that kept breaking the welds on the long cantilevered axle. I will probably modify the system to use a belt drive rather than chain drive at some point. I have to adjust the chain once every couple of months, and a belt drive system would get rid of that hassle. Otherwise, this rig works well, and I only have about $300 bucks in the build.

[Stinger]

After drawing up a few versions, I think I'll build this. Not exactly sure what I'll use to connect to the gear legs, but I'm sure there'll be something at Lowe's or Tractor Supply I can use. I'll have to get measurements and play around with different material types, but the lighter I can keep it, the better.
The center tire is in line with the main tires. Then short vertical sections to connect to the gear legs.

[Andy Young]

I think you may want to triangulate that significantly. In my opinion, your current design is likely to either bend badly or snap at the welds anytime you impart any significant side load, such as when turning. Straight forward and back might work if it’s built heavy enough, but a triangle, with straighter lines of force, could be lighter and still be stronger. You don’t need the base leg of the triangle, as the airplane forms that. Unless you want it for ease of movement of the device.

[andy]

It looks like you'd be putting a lot of strain on the oleos when you try to turn the tow bar with this design. You would have to rotate the tail wheel first so it is pointing forward. Our Air Tractor AT-802F air tankers have welded fittings on the inside of the main gear legs to attach an A-frame type tow bar to a tug but the Maule doesn't have this. It's hard to tell from the photo if you have ABI HD gear legs without fairings. If so, then you might be better off clamping to the bottom of the main gear legs instead of the oleos for a stronger connection with some padding to protect the paint.

Have you considered a remote control tug like the SMARTug M3 or something similar but home-made and less expensive? You could adapt a remote control RC car to control a larger motor and chain drive without a lot of expense.

[Flyhound]

I have to agree with Andy. The right angled arrangement between the crossbar and the extended tow bar would put huge stress on any welds or bolts where the parts join when trying to turn the plane. The tailwheel is a long way back and that moment arm will put a lot of resistance on your attempts to turn the plane from up front. The only planes I've seen use a front mounted tow bar are trikes, or amphibs where the front wheel(s) are steerable. With the mains fixed on a taildragger the leverage is against you with this design. That is probably why there aren't any designs like this on the market for small planes.

[Andy Young]

Again, I think the fundamental concept is good, based on my experience with the Otters, as shown in the photo. Just needs to by designed with force vectors in mind. This one hinges at the hitch end for ease of movement and storage.

[RedOwlAirfield]

Jeepers I must be ancient.

When I was growing up tow bars like this were the standard. No one ever used a tailwheel tug. Of course this was generally on heavier aircraft, but still - it was done commonly. So it would seem unlikely to cause damage under normal circumstances. I can appreciate the healthy suspicion of anything that is not what we all know currently, but the idea works just fine. If the landing gear can take some of those lateral loads that some folks ( not me or you of course) have put on it, it can handle this tug system.