Project Squirrel

[Outlaw]

Once more, haven't touched this in a while, so I figure I'd update what I've done... which is not a lot other than re-brainstorming.

The idea's to use as much as I can from the original variant of Ratatoskr, so the motors, wheels, ESCs, and maybe some of the plastic, but the batteries I'm going to have to replace as they've not been used in ages (Need to find out how to dispose of them safely or if I can even dispose them at all.)

Additionally, to add to that, it'll be a different body style, a more traditional box-ish shape with it's front with a 45 degree wedge, almost like a mini RW7 Thor... with liberties on the design of course.

On top of that, I'd be switching from a linkage system for the axe to a Snail cam sprocket(?) system. Are snail cam sprockets a thing? Because all I'm finding are bike chain tensioners and adjustors, which aren't exactly what I'm wanting... On top of that, I'd probably need to find a motor with a longer axle or a way to extend my scooter motor's axle to accomodate two of them.

So my list of things to do now is this:

-Draw up the design in an art program or attempt to get CAD software working again to make it more feasable
-New Motor Mounts for easier access and security
-See if such sprockets are available in the first place
-New Batteries
-Maybe get the chassis built out of aluminum for a little more rigidity

...that's all I have for now.

[Outlaw]

So, figuring things out still with the axe mechanism... I'd have a better time just going for a standard chain drive in that respect, and with it, get a sprocket that fits on the motor's axle, and possibly just hook up a bike axle and sprocket for the other end of things... I should really think first before saying things.

[Outlaw]

So, with the redesign of the weapon system, I wish to put out a few questions to... well, anyone that does axe weapons done with a chain drive system. Here's what I've got so far;
axe mech2.png
I'm wanting to do a reduction of sorts when it comes to bringing the weapon up and over the bot in order to bring the axe to bear, as to try and balance it between speed and torque in an attempt to get as much power out of what little I have, using this https://www.ebay.co.uk/itm/164336973228 overvolted to 21 volts and a sprocket replacement and getting new batteries to boot, considering I don't trust the ones that I currently have...

My questions are as follows;

-Would the diagram drawn out above even be feasible, what would be the best "ratios" and if so, would it increase power, or would it just slow it down too much?
-Where would be the best places to get such sprockets, along with chains, axles, bushings and keys?
And;
-Would it even be possible to fit all those chains and sprockets into a 5cm gap between the uprights?

At the moment, this is all just concept stuff. So any help with this would be fantastic!

[Ocracoke]

To answer your questions based on my experiences with axe robots:

-Would the diagram drawn out above even be feasible, what would be the best "ratios" and if so, would it increase power, or would it just slow it down too much?

Yes, it is feasible. I do exactly this 2 stage reduction with solid gears in my Middleweight. I would aim, in the FW class, for around possibly 8:1. Azriel (my FW axe robot) uses a single stage 4.5:1 reduction and although the axe is quick it lacks downwards oomph. I'll be addressing that in a rebuild soon enough.

-Where would be the best places to get such sprockets, along with chains, axles, bushings and keys?

I use https://www.gearsandsprockets.co.uk/ for my stuff. They have all you need except keys. Bearingboys.co.uk sell key steel as well as gears et al but you will need to find someone who can machine a key into a shaft. Roboteernat has done mine in the past.

Would it even be possible to fit all those chains and sprockets into a 5cm gap between the uprights?

This I can't answer for you. You need to sit down with a pen, a piece of paper and a calculator to work out how wide each sprocket is based on their engineering diagrams, how wide the chain is and then add them all together to get your answer. When I was working on Jibril, I used CAD and a calculator to work out the overall dimensions.

[Outlaw]

I would aim, in the FW class, for around possibly 8:1.

I apologize for all the questions, my math is absolutely atrocious, but would this mean that in order for me to get an 8:1 ratio, it'd basically be a 4:1 on the first reduction, then a 4:1 on the second? Or would both be 8:1 then 8:1?

[Ocracoke]

Each stage is a multiplier. 8:1 x 8:1 = 64:1 so you'd want say a 2:1 on the first stage and then a 4:1 on the second.

[Outlaw]

Right, I get it now, thank you so much. I'll get to adding everything up and go from there. Many thanks!

[Outlaw]

Quick question (apologies for the continuous amount of them), what would be the recommended diameter for the shaft, from previous experiences if you have any?

[Ocracoke]

Jibril 1.6, the final incarnation of that version, used a 12mm steel shaft for the first stage and a 10mm titanium shaft for the second stage. For a MW, the second stage was woefully undersized and when it was steel, even tool steel, it would warp badly. The 2.0 incarnation uses a 12mm first stage and 20mm second stage shaft, both titanium grade 5. That machine has been flipped on its head and nothing shifted.

Azriel uses a 10mm steel shaft which doesn't appear to be too bad but remember, that gearbox isn't transmitting a whole load of torque. If I was going to rebuild Azriel with something like a 8:1 gearbox, I'd probably go with 12mm titanium on both stages based on experience.

In general, the thicker the better but weight is a thing. I'd probably start at 12mm and see where that gets you. Remember, enlarging a hole is easy, reducing it... eeeeh not so much.

[Outlaw]

So 12mm sounds good to me, and I'm think of using the silver steel. I'm a bit of a dipstick and I looked back at one of my previous posts/questions about shafts/axles... So I may go for the 12mm silver steel shaft.

[Ocracoke]

Silver steel is OK. If you needed a upgrade to the silver steel, I sometimes have used tool steel bolts which are harder to bend.

[Outlaw]

Okay, I'm back with more questions... good lord, I need to get my act together.

So the first reduction chain would have a 6mm pitch to it leading between both the motor and the sprocket it's going to. This being the starting sprocket on the motor: https://www.ebay.co.uk/itm/174202985284

Question is would it be alright for me to swap over to a different size chain pitch and different sprocket to act as the start of the second reduction?

I'm sorry if the question's confusing, just trying to sort things out measurement wise.

[Ocracoke]

Question is would it be alright for me to swap over to a different size chain pitch and different sprocket to act as the start of the second reduction?

Technically yes, you can use a different pitch set of sprockets and chains for the second stage but what is the advantage in doing that? You end up with two sets of incompatible chains that means you have to carry spares for both in the event they break. For the power of the motor, I would honestly stick to 6mm pitch for both stages to start off with.

[Outlaw]

Okay, fair enough. Now for the 1:4 ratio, can't exactly find a 44 tooth sprocket to make the 1:4 ratio work... would a 45 tooth sprocket work? Just wanting to cover all bases here, and make sure I don't end up screwing up.

[Ocracoke]

45/11 is 4.09 so it isn't adding anything signifcant to the overall reduction, you should be OK.