Build Log | Caractacus - Any Tips?

[willcaddy]

for the axe mech i suggest going for the simple scooter motor chain reduction as it works will

Thank you very much! Would you be able to elaborate a bit because this is a very new thing for me!

[Ocracoke]

So it is a scooter motor with a cog that drives a chain connected to another cog connected on a shaft to the axe arm (I am sure Hatchet uses something like this, as does BattleAxe and Blacksmith I seem to recall). Fairly simple and quite effective - I'd go and check their respective build diaries to see the mechanism in action.

[willcaddy]

So it is a scooter motor with a cog that drives a chain connected to another cog connected on a shaft to the axe arm (I am sure Hatchet uses something like this, as does BattleAxe and Blacksmith I seem to recall). Fairly simple and quite effective - I'd go and check their respective build diaries to see the mechanism in action.

Awesome, Thank you very much! I shall go and have a look now

[RogueTwoRobots]

I made an axe mechanism for my robot Onyx a good few years ago. Started off with a drill motor powering it before switching to a scooter motor as the drill motor gearbox was too fragile. Here's a look at the transmission with the drill motor fitted:

onyx_build (1).jpg

It's a 5:1 ratio using 8mm 05B chain from Technobots. Think it's a 40T sprocket on the axe and a 8T one on the motor. Just drilled two holes in the axe arm and large sprockect to bolt them together, then drilled a central hole for the shaft, which was 12mm silver steel. It's a live shaft so I used grub screws tapped into the boss of the large sprocket to pin it to the shaft, and then there were 12mm needle roller bearings in either bulkhead (second bulkhead removed for visibility). Made for a very smooth mechanism.

I then switched to the scooter motor:

onyx_build (52).jpg onyx_build (53).jpg

It was a bit ungainly sticking out the back but it was a huge improvement. That just bolted to the baseplate with M6 bolts and again used an 8T sprocket. The only difference was that I welded the sprocket onto the shaft and got rid of the idler sprocket from the first picture as I managed to improve the chain tension. The axe arm was a section of hollow steel bar so I ran a steel cable from the axe head down to the shaft, round and back up to act as the tether, as specified by the rules.

And the mechanism in action:
https://www.youtube.com/watch?v=60-9-927nPw

[willcaddy]

I made an axe mechanism for my robot Onyx a good few years ago.

Two things, 1: That video is absolutely brilliant! Made me lol! xD and 2: Thank you so much! That is really helpful

I'm actually just in the middle of printing out the templates for cutting the main part of the robot out of wood so i can test sizes etc so this is perfect timing

Will keep you posted how i get on!

Thanks again

EDIT: Forgot to ask a couple of things lol. Firstly, when you say the boss of the large sprocket, where do you mean exactly? Not really sure what boss means lol. Secondly, is the tether there in case the fixings fail so it doesn't fly off mid swing?

Thanks again

[RogueTwoRobots]

Sorry, just saw your edit.

The boss is the protruding cylindrical part that comes on a lot of sprockets. It's a good wall thickness on the 40T sprocket which made drilling and tapping for grub screws nice and straightforward

_20180406_180541.JPG

The tether is in the rules so that if the axe head becomes separated from the arm, it doesn't go flying off, potentially breaching the net roofing of some live arenas and into the crowd. At least, I think that's the main reason. It's more for axe heads that are bolted onto arms where the chances of the bolts shearing is reasonable, but on Onyx the axe head is welded on, so it's a bit redundant, but dems the rules

[Maxamuslead]

I think that's the main reason. It's more for axe heads that are bolted onto arms where the chances of the bolts shearing is reasonable, but on Onyx the axe head is welded on, so it's a bit redundant, but dems the rules

Sorry for hijack but is this required for any axe head evan if the shaft and head are one of the same E.g. Hatchet's ?

[qbnut]

It is strictly in the FRA rules but I think that EOs bend them on this one, especially in the age of spinners. A chunk hit off in spinner blow is in my opinion likely to do more damage than an axe head falling off or being thrown.

Battleaxe had a chain tether at Insomnia last year and this was accepted in tech check though it broke in the 722 battle when the head came off anyway :/ It's now on a steel cable tether. Broadax on the other hand is one-piece Hardox so I don't believe it will be required depending on the EOs discretion. Though if in any doubt about the robustness and safety I would add a tether. You are right as far as I know the last Hatchet revision wth the one-piece also did not carry a tether.

It might be the case of still being needed for arenas without a roof I guess.

[willcaddy]

Thanks Everyone! and a question about the axe motor ESC?

Hello again everyone

Sorry for the really long update on this build. I have had a carpel tunnel operation which has left me unable to do a lot on the robot but it is getting better!

I just have a question about the ESC for the axe. If I'm using something like a 300w scooter motor, the first question is probably obvious lol but what ESC would you recommend based on the motor is probably going to do a fair amount of stalling in a battle?

Second, would it be a case of wiring it up the same as the drive motors or is this liable to snap the chain if you go to mad with it? Is a set up similar to a servo what you need? and if so, what would you need to do to add that functionality?

I hope that all makes sense!

Once again a big thank you to you all for taking the time to help me out! I have never known such a wonderful community

All the best

Will

[Roboteernat]

Glad your recovering

My axe is run from a 150w? scooter motor through a 2 stage chain gearbox giving 5:1 ratio, so not powerful, however it was rnning from a 30 amp electronize esc - as i didnt have a spare TZ85a esc.

It was stalling allot during my time at ER 3 fights, and didnt suffer, nor did the ESC get warm.
thats my insight into it if its any help.

[willcaddy]

Glad your recovering

My axe is run from a 150w? scooter motor through a 2 stage chain gearbox giving 5:1 ratio, so not powerful, however it was rnning from a 30 amp electronize esc - as i didnt have a spare TZ85a esc.

It was stalling allot during my time at ER 3 fights, and didnt suffer, nor did the ESC get warm.
thats my insight into it if its any help.

Thanks a lot for the reply! Was very helpful Just one quick question, did you wire it up the same as a drive motor (forward on the stick changes speed) or did you do like a servo type setup (stick position is the same as axe position)? (Hope that makes sense!)

Thanks again

EDIT: Just found your test video on you forum post lol it looks like you are doing the former xD but if you could confirm would be much appreciated!

[Roboteernat]

I understand.

I had no feedback from the motor position, so stick forward is drive motor forward, back, drive motor back.
The only thing stoppuing it from going further was the chassis/floor.

a video of it running is on the build log: http://www.fightingrobots.co.uk/thre...ld-of-fw/page8 first post on page 8.

Im using a servo tester to control the motor ESC so i didnt have ti wire in the TX.

EDIT: just seen your edit and that you found the vid

[willcaddy]

Thanks a lot You have been awesome

Can i just ask one more thing, did you use a brushless or a brushed scooter motor? I don't mind getting a 85A ESC of either type but just wanted to make sure which was best for the axe xD

Thanks again!

[PaulusSmallus]

You are using a brushed motor for the axe, so you can either use an ESC for a brushed motor or use an ESC for a brushless motor and change the firmware so you can use it in a brushed mode.

[willcaddy]

Nearing completion xD

Hello everyone!

The robot is really coming along now and with loads of great advice from Roboteernat its finally nearing completion xD

Just a few questions remain which i would love to get all of your input's on!

Firstly I have read that Hardox 450/500 is the go to for a hard wearing axe head so I would like to use that but I just wanted to get your opinions on what design i should use? Is a hatchet style blade beneficial verses a pick axe style blade? I would have thought a smaller point would pierce better but I see a lot of robots going for a wider blade. Your thoughts?

Also along that train of thought, Is there anything i should be aware off when using something like Fusion 360 to design the blade and export it for cutting? (also any recommendations on where to go to get it cut? xD)

The other thing is I went with the BotBitz 85A ESCs and I found out from Roboteernat that the original ESC these are based off of has been discontinued. I hear the FeatherTwo's from Rory are pretty darn good so i was pondering switching the ESCs out for a FeatherTwo and using the one BotBitz to drive the axe motor.

Again any thoughts/recommendations on that idea and other brands of ESC?

I will post a link when i upload the latest video of what im doing too if you guys are interested

Thanks in advance!

Will