One of the goals I have for Lawnny is for it to be able to move my boat into its parking spot behind my house. While it is possible for me to back it in directly with my vehicle, it's an extremely tight fit and the margin for error is just an inch or two on each side. Because of this, I generally park it by pushing it in by hand. Because I have a relatively flat driveway, amazingly it is possible to push the 2,500+lb boat trailer by hand, but it's not exactly fun.

I'd like to mimic a trailer dolly, similar to this:

But instead of pushing it, I want Lawnny to do the work for me.

Now there are a few major concerns here:

1. Will the weight of the boat trailer crush Lawnny?
2. Will Lawnny have enough power to move the boat?
3. Will Lawnny have enough traction to move the boat?

Will it crush?

Success: 🟢

After my experiments today, I can say..... it will not! I wasn't really worried about the frame— the 2" receivers are made from 1/4" steel and would probably support a 747. I was mostly worried about the motor axles. The treads are connected directly to the motor axles with no support from a pillow-block on the frame, so the motor axle itself is pretty much taking all the load. The other issue is that the treads are offset quite a bit away from the motor, and this creates a lever-arm which increases the force load on the axles. I was extremely worried they would just snap or strip a gear.

Apparently they've taken this into account when building these mobility scooter motors (probably thanks to the obesity epidemic in America), because there was absolutely no issue taking the weight. I think the tongue weight on my boat trailer is around 350 lbs, and it seemed to barely register when I lowered it on the ball hitch.

Will it have enough power?

Success: 🟢

Yes. It was able to get the boat moving without any trouble. Buuuuuut there is more to the story below....

Will it have enough traction?

Partial Fail: 🟠

As you can see here, it did not.

But I'm going to say it wasn't a completely fair test. This part of the driveway is slightly uphill, and I was starting from a complete stop (no momentum) and the ground was wet from rain.

Did I fully think this through?

Fail: 🔴

As you can see from the following video, I did not...

Remember above when I told you I got the boat moving? Well I didn't really think about stopping it...

So I'll start out by saying that I was very aware up front that Lawnny would have trouble towing from this position if he moved in reverse— there is nothing to stop him from tipping over the front. My solution to this problem was always going to be "When towing: don't drive in reverse. if you need to go backwards just turn Lawnny 180° in the opposite direction and move forward". You can see this working in the first video.

But what I didn't account for was the cruel mistresses of inertia and gravity. Lawnny can get the boat moving without any trouble, but when Lawnny wants to stop the boat, the weight of the boat and the slight slant of the driveway say otherwise. It's pretty much the same as if Lawnny started to back up, which rendered my so-called solution useless.

Anyway, I'm starting to think that towing such a large trailer may not be the best idea. I think I could solve the tipping issue by putting another set of wheels in front— which is super easy to do because of the modular nature of the hitch receiver frame— but it won't solve the braking problem. Luckily my driveway is relatively flat so I'm less worried about gravity running away with it, but the inertia problem still exists.

At the end of the day I'm still interested in getting this to work, but I'm going to tread lightly— I don't want a 2,000 lb boat careening down the neighborhood street dragging a helpless robot along for the ride.