Deathly Hallows - FW - No-IP-Rocs

So after the learning experience of Alligrator I have a new idea.

Basic idea is to repurpose an MY1016 to power an axe/hammer.
I'll reuse the electronics for controls too.

New brushed geared 24V DC 500rpm motors for drive.

Chassis shape I have some ideas but not fixed yet. But it will surely approximate a triangular prism. The slopes facing forward and back. The weapon should be a self righter.

After the issues with chain drives I am tempted to use fixed gears or a belt drive would be an option to reduce the shock to the weapon motor. Any recommendations?

Fixed gears for the drive. I've seen the setup on Satanix with speed 900 motors (and I think shakey's got a brushess setup for sale at the moment) and it works really well, nice and robust.

Belts work but only when they have tension. For an axe, I found fixed gears work when the casing for the gears are robust, which mine wasn't. I am sure some of the HW axes use a fixed gear system when driven off of a pneumatic ram and I am sure Hammerhead (one of Team Shock's FWs) had a similar system? I'd probably try a toothed belt if only to have something easily replaceable if it breaks.

Been away on business trip last week. Unfortunately looks like I'll be away a lot over the next few months. It's going to be hard to find blocks of time so this will be a slow build. I have a horrible feeling that this year will be a washout. But if I can keep designing, making part lists and building when I am at home, but I'll get there eventually.

I'm still thinking about the axe mechanism. Whether to fix the larger geared spur to a live axle and the weapon arm to that live axle. Or fix the arm to the larger spur and have a dead axle. This second option is my preferred as it has less failure points, and I can probably drill the necessary mount points myself in a solid gear.

I've had some time to play in CAD and started building the first parts. I have some new 24v 550rpm geared motors. These are a lot lighters than the MY1016's.

I have made some small purchases.

Banebots wheels and hubs arrived
Some steel bar for the arm
A steel rod for the axle for the axe
Also a motor controller that should handle the amps needed for a full stall on the axe.

Here I am wondering about using and Arduino to control it. I realise it adds complexity, but it could react a lot faster than I could to the stall, reset and fire again. More pondering required...

I won't have time this weekend to build a test rig, but the weekend after, that's what I want to do. Build a test rig for controlling the axe

Tested the new wheel drives. Seems to be a big difference in speed between forward and reverse could. More severe than I have seen before. Should be possible to address the balance with controller.

I have started working in onshape cad to convert my sketches to real drawings.

It's ticking over

If it were me I would keep it as simple as you can.

With most transmitters you can set an exponential curve that means the slightest twitch on the channel puts it at 100% throttle / throw. You might find that's sufficient depending on the axe mech. This is what I do on all of my axe Featherweights.

Whilst you could Arduino it, there's more to go wrong, plus if the intention is to full-on the channel on a transmitter button press, your chosen ESC would need to handle a 0 -> 100% change without errors for the speed at which you want to change it, as some would see that as an invalid value change if too fast. You would have to experiment to find what the absolute fastest change value you could get away with is.

Another more technically challenging solution I have seen is you cut out the middle man and instead code custom firmware for your ESC itself to do it, though that's an advanced solution.

ok for the axe. t8f (8mm scooter google it)chains work great for a scooty axe they have bean proven to work and can take the power. For ESC i suggest time THIS it is the replacement for the tz85 and it best ESC which is still in procduction. i would suggest a Feathertwo Single channel but they are out of production and people who have them are not that willing to sell. on the Arduino front i did dabble with the idea but speaking to Shakey it is a bad idea as the Arduino can get confused and fire the weapon randomly. the only person i know who has used a Arduino in full combat is Rory Charlesworth in Aegis acting as a limit switch controller.
For drive 550rpm sounds really low so either you are looking at beetle gearboxes or a really high reduction, you got a link to them ?

Thanks - your right. The switch speed could be too high, though I could program a pause.

I'm going to see how it can go together next weekend. The motor controller is not the typical unit and built for an Arduino but nothing to stop me wiring the pwm signal to the RX directly. It is a real experiment. I intend it to run max speed no ramp up, could be a dead end, but worth a bash.

I'll give details when I try it out.

I'm sure I'll get the controls for weapon sorted. I am having more issues trying to imagine how to fix the weapon shaft to the motor. So I fit a small spur gear to drive shaft say a 1.5mod 20t then a larger 1.5kod 80t as the final drive. So 4:1 that will make it around 700rpm. That gear will have a central bore of 15mm. Now I can get a gear that has a hub with two M6 threaded mounts if I want a live axle, in which case I would have to then fix the weapon arm to the axle. Alternatively I could not fix the larger gear to the axle, but fix the weapon to the gear. This is could drill and fix with bolts or I'd need to get welded. ( Wish I'd bought that welder at Lidl a few weeks ago). The prior option has two failure points and unless I drill a hole in the axle I am not sure this is really that strong. The latter option seems to me stronger but if the weapon failed it would mean a new gear.

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Alternatively I could not fix the larger gear to the axle, but fix the weapon to the gear. This is could drill and fix with bolts or I'd need to get welded. ( Wish I'd bought that welder at Lidl a few weeks ago). The prior option has two failure points and unless I drill a hole in the axle I am not sure this is really that strong. The latter option seems to me stronger but if the weapon failed it would mean a new gear.

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This is how I built the axe on Kaizen. A CIM motor drives a Mod 1 16T gear which in turn drives a 48T gear on a dead axle with the axe directly bolted onto the gear, giving it a 3:1 reduction.

Ok what scooter motor you are using. How heavy a axe head and how long a handle. This will effect what ratio be the best. Also gears are very heavy. I really do suggest using chains but if not. Use 12mm bushing as they have a 15mm outer thickness. Stick them into the weapon spur gear and use a dead shaft. For attaching the axe to it bolt it. However attaching the spur gear to the Motor will probably need a welder. Side note HDPE bot great at keeping gears meshed. It deforms too much.


EDIT: like this

Attachment 8408

But i a chain drive will be lighter and just as effective

I have made two axes bots with chains and one with spurs, and I'll say that there's no right or wrong solution - each has advantages and drawbacks. You do have to be more precise with spur gearing and as mentioned above, mounting them into HDPE doesn't really work, you would need more rigid bulkheads to use them.

On the other matter, go bushings all the way. Whilst bearings work they make maintenance hard, as you have to take the whole thing apart to change or fix. With bushings and a dead shaft it becomes an easier job to just slide things out if you need to fix.

Quote:

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Originally Posted by qbnut

I have made two axes bots with chains and one with spurs, and I'll say that there's no right or wrong solution - each has advantages and drawbacks. You do have to be more precise with spur gearing and as mentioned above, mounting them into HDPE doesn't really work, you would need more rigid bulkheads to use them.

On the other matter, go bushings all the way. Whilst bearings work they make maintenance hard, as you have to take the whole thing apart to change or fix. With bushings and a dead shaft it becomes an easier job to just slide things out if you need to fix.

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yes you are right BUT with scooties due to how they do not have face mounting hole ( legit only style cannot be found in UK and importing is not worth it) and with how toqurey they are i would suggest mod 2 min. And thinking about all the scooty axe (sams 4 your one Craig and my 2) they where all chain driven. Admittly I copied Sam set up but it works and works well

So much great feedback!!!

I have a MY1016 motor
The shaft outside the casing is a little over an inch long, half inch reverse threaded, but also it's got a flat edge the length of the thread.
I have measured repeatedly and it seems the shaft is 8.0mm I thought it would be 1/3" but appears not.
2750 rpm 24V says 300W and also two 250W units much lighter that were on alligrator
It's very torquey, the smaller motors on alligrator seemed easily powerful enough to let me ride on him if the chassis would take it - lol
Internal chassis and structure will be steel or aluminium

For the arm length, I actually plan something unusual. Relatively short 200-250mm with the axe being inside the body, rotating round 270° to impact the target. Yes I know it sounds odd, I'm probably also more likely to have issues as unusual, but I'm not one to follow the herd. If it fails, I'll extend the length and have the sting outside the body.

Sting..... Oh yes so no-ip-rocs backwards is.... Scorpion
And I have purchased a lovely stinger...

I should probably try and make a simple basic design first, but there is a lot of fun in designing and coming up with ideas

how heavy is axe head ?

Not that heavy. 133g

The arm will have more mass. This is the sting!

Attachment 8409

Erm yeah that's not gonna much damage. To give you a idea my hammer head is roughly .750 kg Craigs round .4-.5 kg

But the arm mass is part of the calculation not just the mass on the end. Though certainly the force generated by the same mass towards the point of pivot is less than that towards the end of the arm. So if I had a 1kg or 2kg arm the hammer point is only that, the point through which all force is dissipated/exerted. Perhaps I need a really heavy arm, or am I wrong?

Yes the arm will add energy but adding to the head will add more for the weight cost. Also increasinf the arm length increases power

Think of a disc. The more mass to the edge (higher MoI) more of the energy is applied to the target. Same idea with axes just less time to build up energy. I got a calculator on my pc I show you later the difference.

I understand and agree the greater the mass and further from the pivot the greater the impact.

Found a nice animated gif here:
https://en.m.wikipedia.org/wiki/File...a_examples.gif
https://en.m.wikipedia.org/wiki/File...a_examples.gif

I want it to be able to fight, but I'm willing to compromise for a bit of style over performance. ;)
First I'll get the motor control sorted then investigate if my idea is viable. Really appreciate your input. If you have a link to a calculator id appreciate it. I know one was posted here before but I can't find it now.

FYI The reason I was looking at spur gears is the bad experience I had with chains on the drive for Alligrator. Always jumping off.

Hello world! I'm back. Been a busy time at work and it's not going together any easier but I'm persevering with the project. Why does it always seem that I'm trying to work on a project when it's below zero outside?

Acquired a welder at Lidl and seems to do the job
Also bought the gears I need

I want to rig a test setup for a weapon test. Get a handle on how I'll operate it and see what kind of power it has.
I can attach extra mass near the end of I think it's needed.