Some time ago, and I’m not prepared to say long, I stumbled on a project in Make magazine, the Fetch-o-matic, we have a ball obsessed dog and I decided I had to make one. Overall the project was simple enough to make, I made a few modifications, mainly to suit the motor I got, the pictures should make it all clear.
A couple of pipe clips and the end of a broom handle make up the adjustable height leg
Detail of my pivot design. The ‘pusher’ bar was part of the original wiper mechanism, I just has to flatten the bar . Screwed to the threaded motor spindle is a small turned piece, which acts as a nut to hold the pusher in place, a spacer to set the main bar height and a spindle for the bar to rotate around. The top lock nut is not tight against the bar so it can rotate freely
These show the microswitch and it’s operating lever. I had this switch in my parts bin but the weight of the tennis ball was not enough to operate it. I used a piece of old copper clad pcb and some duct tape to make up a lever
This is the underside. The motor is attached to a steel plate, if I’d bolted it straight to the ply case the spindle would not have projected high enough inside the case
The underside again, the microswitch is held by the small piece of wood but it also needed hot glue to stop it moving. I wasn’t able to bolt it in as the whole thing was about the same depth as the ply. The battery is loose at the moment so I can remove it quickly for charging. I could just fix it in place and add some charging points for it. I have not fitted a separate switch as the microswitch does this job. I guess there is a small chance something might fall into it when it’s stored and cause it to activate, but I can just disconnect the battery.
Another view of the inside, the loose end of the spring attaches to the lid.
I Finally completed it over the weekend, at least to point where I could try it with the dogs.
I’ll start by saying that when I built the dog kennel, it took a good few months before either of our dogs showed any interest in it. I’m hoping the same will happen with the fetch-o-matic cause I had a frustrating Sunday trying to get Rylie to drop the ball into the hopper. I was depending on her ball obsession and her habit of dropping a ball anywhere where I happen to be focussing my attention, If I hang out washing I usually find the ball in the washing basket, If I dig up some potatoes the ball gets dropped in the hole, If I shovel some compost the ball gets placed in the wheelbarrow, you get the idea. No matter how much attention I gave the hopper the only way the ball ended up in it was if I put there. Just to make her point, on Monday morning I was drinking a cup of tea outside, Rylie jumped on the table and dropped a ball in the mug.
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Our other dog, Seamus just barks at the machine whenever I put a ball into it but he does that when I throw things for him too. At least he did learn fairly quickly to get out of the way.
There are a few improvements to make still, I think the bar will wear out where it pivots on the shaft so I would like to create a hub for the bar, connected to the shaft using a proper bearing, should be easy enough to make on a lathe. The lever I made to operate the micro-switch uses duct tape as a hinge, this works quite well but I think I need a tape with stronger adhesive. A stronger spring or maybe a weighted bar may also help give it more range.
Update: Made a little bit of progress with Rylie today, got her to drop the ball in the right place a few times but she’s not getting the connection between dropping the ball in the spot and having it launch. Originally the whole thing was painted white but I’ve now painted the hopper a different colour, which may have helped a bit. I’ve gone for Blue hopper which should be a colour dogs can perceive. Seamus, as ever, just barks at it.
Rylie does seem more interested in actual interaction with me than I was expecting, as Jonathan suggested might be the case. We may have to arrange for an event in a local park so we can bring our respective dogs and see what chaos ensues.
Last Updated on 22 August 2015 by Rob Hamblett