OutdoorKing Repair Forum Forums Finding and Swapping Idle Chatter Boat / Caravan - Powered Dolly

I had a bloke come over this morning after some Greenfield bits and after discussing this with him he explained he wanted to build a caravan dolly for moving his caravan/boat around his yard. After much discussion we decided that using the rear transmission from the Victa ride on mower I had here he could possibly even use a battery drill on the transmission pulley to drive it.

Not sure if it would be strong enough We could also use the existing pulley and something like a 12 volt starter motor, maybe even bolt a ring gear to the existing pulley? Has anybody attempted anything along these lines?

A starter motor would be the go more than enough torque to do the job if geared right power consumption would be high so battery wouldn't last long . An old battery mower motor would be the go should have some endurance compared to the starter motor idea. .

I've seen a modified cylinder mower used for that purpose removed the rear roller added a axle in its place used ride on wheels use to easily move 2t had a tow ball front and back to sort the reversing issue out

Captrusty, gives me a few more thoughts, maybe we could mount a Powertorque directly on top of the pulley and use a flexible pump coupling. Being a flat top motor it keeps the height down, and being a gearbox/drive unit it already has forward and reverse. Might be the way to go

Just had more thoughts, it is going to need a clutch to be able to select neutral, so maybe not an easy idea

You can buy 12V versions of a powered jockey wheel for under $300 on the Bay of Fleas just now; http://www.ebay.com.au/itm/Motorize...Power-Mover-Dolly-350W-Top-/252735087413

A google for 'powered boat dolly' then selecting 'images' brings up plenty of examples, too.

My brother has a ski boat, so he snaffled the old man's Greenfield Tractor ride-on, when the old boy gave up mowing lawns. Fabbed a towball mount for the front of it, and uses that to manoeuvre the boat trailer [it lives in the garage - the cars got a carport]! He's got a pop-top caravan now too, so it would get used for moving that as well.

Thanks Gadge, just when I thought I was onto something. I had better not tell him cause I sold him the gearbox and wheels for $50

Ok so it is getting to the stage it is working reasonably well just a little bit too fast. A speed controller would fix this problem but I'm a bit unsure what would work

G'day Norm,

What sort of current rating does the motor have?

Not sure Gadge, he has taken it away for another test run, I'll check it out when he brings it back. Apparently the motor is from a power steering unit on some Nissan

Righto, mate.
Once I know what load it has to handle, I can find you a speed controller.

The way to go is what's known as a 'PWM DC load controller'. What it does, is to send an output to the motor that consists of a series of DC current pulses. Longer duration pulses = higher speeds. They're cheap as chips, these days, for 12V.

Edit: I should explain here, that these solid state controllers are used as high-efficiency dimmer controls for DC battery powered lighting, and as variable speed controllers for conventional DC drive motors, such as we have here. PWM stands for 'pulse width modulation', BTW.

great looking idea you have built.
put a bigger big pulley will slow it down.
or also add a 3rd pulley n 2nd belt

Hi Gizmo, have been talking about fitting a bigger pulley but not sure how big to go. Trying to keep it as compact and simple without fitting another pulley/shaft setup but you never know, it is not that much too fast but could make manoeuvering the caravan/boat into position a bit tricky

G'day Norm,
Another thought has occurred to me; once I have that current rating, I can see if it will be possible to use a simple DPDT centre-off toggle switch for F-N-R selection. Or if it'll need a couple of relays as well as the switch.

Hi Gadge, at this stage we have F-N-R selection on the gearbox but my concern is if he is on the sloping ground and he puts it into neutral the thing might become a billy cart before he can get it back into gear. It also may not release from the gear due to the load on the gears so forward/reverse switching could be a good idea.

Hi Gadge, any idea how the pulley is fitted to the gearbox, is it splined, keyed or threaded?

G'day Norm,
Dunno offhand, but I'd think that splined or keyed would be most likely.

Hi Gadge, it was keyed and he had it already off when he brought it over. I fitted a bigger pulley he bought, but I don't think it will make that much difference, he has headed off to try again.I took some pics of the motor but the flash reflected a bit much, there is little info on the motor apart from a bar code and these numbers
JTEKT JS- 00314 Z not sure if you can work anything out from that.

Why not use the common as grass blades Ryobi 31cc lawn hornet engine? I'm sure it is up to that with the right gearing and all the other assorted attachments they used to come with.

Mowerfreak, due to the sloping ground this is going to be used on we are going to need to be able to switch the motor from forward to reverse, because of the load on the gearbox we are unable to change gears. Only way of doing this is by using a DC motor for the drive

Upon further pondering, battery electric is probably best for this job.
Keep us posted.

It's both easy and cheap to set up; the most work is making up the mounting panel for the switch and relays. Or they can be set up in a small diecast aluminium box, which can be weatherproofed quite easily.

30A rated 12V SPST automotive relays are cheap, and the switch is ~$5.

For example: Switch - https://www.jaycar.com.au/dpdt-6a-240vac-heavy-duty-centre-off-standard-toggle-switch/p/ST0576
Relays - https://www.jaycar.com.au/products/electromechanical-components/c/22?q=%3Arelevance%3Acategory%3A221%3Acategory%3A221E&text=