Motor for axe/mace

Hi. After asking around about various things including pneumatics but have decided that might be out my reach at the moment for a first attempt at a featherweight.

Me and my friends (after many arguments) have decided upon doing an mace like weapon. The issue with this is finding a motor that we can mount to the robot and then connecting the weapon to it.

Does anyone have any ideas to do this? Suggested motors and mount ect. The easier the better. It's our first featherweight so if it's a bit rubbish that is not such a worry.

The normal motor I've seen for an axe is a scooter motor in the 200-300W range (example:https://www.ebay.co.uk/itm/Electric-...e/184650912002). In theory, with the right gearing, even a 775 motor might work, it all depends on the gearing.

Thank you. We will be using a battery that is 11V and the motor you linked, and most of what I have seen on ebay, are 24V. Will they work on 11V or would that be too underpowered?

Its going to be underpowered. It'll move sure but it's going to be underpowered by over 50% to the point where I can't really see it performing adequately, even if it is going to be flailing a mace. 3S LiPo (I assume that is what you are using given the voltage?) is definitely on the low end of the spectrum foir FW voltages, espeically when there is more weight to carry with an active weapon.

You could potentially use a 12v scooter motor that will run at full capacity, but tend to be 150 watt or abouts. I used one in wanna choppy, an axe bot that was low in height so had to use a smaller motor. It still had an impressive looking hit, but in comparison to axebots using these bigger motors, it wasn’t as impressive in damage. That was running on a 5s or a 4s battery, so I did over power it slightly. I used a 6.2:1 ratio with chain.
Mine was I think a ZY6812 motor

One option for an 11.1V system is a 'CIM' motor. They're rated at 5300rpm at 12V and not too expensive. The downside is that it would need gearing down, perhaps around 10:1, but that would be true of most scooter motors and axe systems so depending on what tools/experience/workshop space you have, it may be within your means.

In terms of mounting, I believe it has threaded holes in the front face, so you could either drill corresponding holes in a vertical chassis panel or make a 90 degree L bracket to mount it in your robot depending on your design.
A 10:1 ratio may be quite difficult to achieve in a single stage transmission using chains and sprockets, so it might be easiest to use spur gears. I know Lucy (Ocracoke) has done similar with limited tooling so she may be able to provide more detail.

Here's a link to the motor: https://www.robotshop.com/uk/12v-531...RoCUjcQAvD_BwE

I have indeed used CIM motors on the original Kaizen axe, Azriel 0.9's axe and still in Jibril's drive system. They are quite robust little motors but they aren't especially torquey. They do indeed have two mounting holes (10-32 imperial size screws) on the face.

You can see the axe mechanism on Azriel 0.9 from 6:30 as below (from RL Grantham 2019, apologies for the dodgy camera work):

https://youtu.be/JsXZ8t9PRo0?t=391

As far as gearing goes, yeah, I use spur gears on them. The one in Azriel 0.9 as above is a 3:1 MOD 1 single stage setup (and I wonder why I couldn't self right... :P) and looks like the below:

Attachment 9826

The trouble with single stage transmissions is that although simple, you do end up not always being able to reach the desired ratio and, especially in the FW class, weight of the output gear is a factor. One of the big 127T gears I use in Jibril is 2.1kg and I use two of them. However, if you were to go with this setup, 1x 12T 8mm bore MOD 1.25 gear and 1x 120T say 12 or 15mm bore MOD 1.25 gear will achieve 10:1 here. Just make sure it is lightened.

As far as attaching gears to shafts go, on the pinion side, you could get away with drilling a slot into the keyway for a grub screw to sit in but this depends on how heavy the swinging mass is so I'd recommend drilling the shaft and bolting it. Same for the output gear if you can reach it with a drill but if not, it'd be either a keyway cut or welding the gear on (I am currently going through that challenge with Jibril as we speak). Some lockthread wouldn't go amiss either, just ensure it has time to set fully.

Drilling gears to attach shafts and drilling shafts to attach gears with isn't hard but is time consuming. Slow as you can, plenty of drilling lubrication and it'll work. I would recommend a drill press if you can get access to one to ensure a vertical drill hole.

Hi guys. Thank you. CIM does look like a good option. I have never used gears as I am very new to this stuff so have a few questions that may seem silly.

1) Where do you actually buy them from? Do you have to buy them individually or do you buy them in a pack?

2) The CIM motor in the link looks like it has a shaft that would need an 8mm shaft hub attachment. Similar to question 1 where would you get a hub that is a gear thing?

3) Really silly question now. With gears (and for example in the picture Lucy sent above) what do you use to join the two pieces of plastic together and what metal bars do the gears go onto?

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1) Where do you actually buy them from? Do you have to buy them individually or do you buy them in a pack?

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The link Jamie posted is where I got my set from.

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2) The CIM motor in the link looks like it has a shaft that would need an 8mm shaft hub attachment. Similar to question 1 where would you get a hub that is a gear thing?

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The gears I get (from gearsandsprockets.co.uk) have hubs attached to them though not all have hubs. They are labelled if they don't.

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3) Really silly question now. With gears (and for example in the picture Lucy sent above) what do you use to join the two pieces of plastic together and what metal bars do the gears go onto?

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The only thing attaching the two sides together in that is the shaft though technically, they aren't "connected" at all since the shaft doesn't bite into the plastic holes it sits in so it's better to think of it as a carrier. Each side sits on L brackets.

Both Azriel 1.0 and Jibril 2.0 have a big bolt running in the back of their carrers to hold the back together to reduce flex.

In Azriels case, the output gear sits on a M10 bolt which has nuts and washers to form the front brace. For long term engineering use, that is a terrible idea but let's face it, fighting robots are often short term and limited time use machines. If it was a spinner running on a bolt like that, it'd wear out very fast but in this case, I don't see it being a problem. There is a video in my build thread showing the rebuild of the carrier where it shows this.

In Jibrils case, there is a idler gear on the front of the carrer which is held in place by two shaft supports With the back support, the 12mm shaft at the front and the big 20mm shaft up top which will have holes drilled in to keep the shaft in the bearings, that makes a strong structure. You can see this in the latest build video I did.

The shafts in the picture is a chromed steel 10mm shaft which I got from gearsandsprockets.co.uk. Jibril is supposed to be using 12 and 20mm titanium shafts but I don't have the proper tooling (yet) to cut them quickly. In light of that, it is currently using a 12mm shaft cast off and a 20mm 316 (I think) stainless steel output shaft.