Fiest [beetleweight]

[ewan]

Continuing the trend of starting projects and then starting yet more before the first is finished: here's another beetleweight. It's a great class to build in, especially with the range of RC/model components available relatively cheaply. I don't expect this one to do much but fail spectacularly, but it's an experimental concept. Inspiration comes from 'Gene' on the RFL forum, a while back he experimented with a kinetic axe (himself possibly influenced by the likes of Team Whyachi's Warrior), which looked like so:



I don't think it actually ended up in an operational machine but the concept was sound in my eyes (and pretty brilliant in that that 'trigger' for the axe is simply braking the flywheel motor). So I drew:



Key differences with this idea are a horizontal flywheel and cable-drive to the axe arm (notice the 'cam' around which this cable would run). The bottom bits may look like a bit of a scramble - that's just me trying to work out how to fit all the bearings & firing mechanism into the height of the thing. A key issue is how to transfer a ~6000rpm disk into a sudden actuation, this will hopefully be done with a chunk of steel hitting another chunk of steel, without either breaking?...
Continuing the trend of being a bit weird, different and likely to break I've decided to use car-steering also (a'la Killerhurtz of old/The Judge). At the pile'o'parts stage at the moment, don't expect this to be finished before the end of summer! (along with the featherweight & electric scooter rebuild...):



Thoughts?

[mark_m]

Re: Fiest [beetleweight]

Cool! I'm also a big fan of Gene's work. I'm interested to see how you connect up the flywheel.
If you're going for an axe robot with killerhurtz driving style then you've got to include a KHz style axe head:


I'm not sure if my 2mm polycarb top armour will stand up to your axe but can't wait to find out. When this arena going to get built anyway?

[ewan]

Re: Fiest [beetleweight]

May well go for something similar, or even like The Judge's in its last guise:



Will have to see about damage ability - no chance it'll compare to a disk, though at least hopefully it'll look cooler!

[Ellis]

Re: Fiest [beetleweight]

The Judge is a truly epic robot. Anything similar to it would surely be terrifying! I can't wait for this build!

[ewan]

Re: Fiest [beetleweight]

Half way there with a prototype flywheel-clutch.



Spins up to insane speeds (this is my first foray into brushless motors..) and then if the motor brakes the flywheel quickly climbs the shaft (mounted at both ends with thrust bearings). Now to construct the other 'engaging' half to do something with the energy

[ewan]

Re: Fiest [beetleweight]

Got a little further, this is working well as a proof of concept





Changed to a timing pulley drive which certainly helps when braking the motor - the round belt would slip and occasionally jump under heavy loading.
Shortened the threaded shaft and added a 'toothed' assembly above the flywheel which it's designed to engage with. This is disconnected from the threaded shaft and only turns when driven by the flywheel (lots of thrust bearings). I'm yet to connect this clutch part to any loads but when testing it snaps around nice and quickly which is promising (and the flywheel continues to unscrew itself out of the assembly as there isn't a load to stop it..)

[typhoon_driver]

Re: Fiest [beetleweight]

a very interesting concept you have there. I will be curious to see how the brushless handles it and how much energy you could get out of the mechanism

[ewan]

Re: Fiest [beetleweight]

Built the basic chassis of the machine, focusing on the flywheel mechanism before worrying about drive etc.





You can see a steel cable running from the top of the dog-clutch which will be attached to the actuated part (still going for an axe first but could really be anything).
When running up to about 1/4 speed and braking the motor, the flywheel ran all the way up the threaded shaft, pulled the cable all the way in and jammed- need to add a load before trying anything faster. Should get a basic axe mounted and tested tomorrow.

(Yes the tablecloth hurts my eyes too..)

[ewan]

Re: Fiest [beetleweight]

Finished the axe mountings and gave a test run with just the cable-pulley in place (no axe arm) but the cable kept jamming either on the clutch or pulley parts. I'm going to find some thinner bike brake cable and give it another go by the end of the week.

[Ellis]

Re: Fiest [beetleweight]

It will be really interesting to see if this is a viable way of making a powerful weapon. If you get it axing, please get some video!

[craig_colliass]

Re: Fiest [beetleweight]

Looks good,
I don't know if the brushless will like the abuse it will get but if you don't try you will never know

For my axe mechanism on Gabriel (feather)
I am using an un-bustable 150w brushed motor that weighs a tonne.
The drive is chain 1-4 reduction running a tri-lobe cam with an axe arm connected via a bolt
the idea is to run the motor for about 3 turns before it engages the axe arm 2-3 turns more
and the axe hits something
to prevent the motor stalling there is a torque limiter fitted.

[PJ-27]

Re: Fiest [beetleweight]

What does the cam do?

[ewan]

Re: Fiest [beetleweight]

Looks good, also unsure why you're using a tri-lobe cam though?

Hopefully by slowly releasing power to the flywheel on spin-up rather than direct-driving an axe the beetle's motor won't be in danger of stalling, the damaging part will be when the motor brakes, but no problems just yet (though not run near full speed so far..)

Bike cable should be here tomorrow, will put up a video then

[craig_colliass]

Re: Fiest [beetleweight]

Re the cam
It is not used as a cam like in an IC engine. in fact it could be circular. I just used the phrase for identification purposes with the picture in the previous post.
To explain there are three bolts through the cam, one has the axe bolted loosely, so the axe arm can pivot on the bolt. the other two bolts are for engaging on the axe shaft on either the strike or the retract mode.
As with all these type of things the reality is a lot simpler than the written explanation.
I hope to run a video of the operation so you can see it and then you will see how easy the mechanism is :shock:

[Ellis]

Re: Fiest [beetleweight]

I think I can see how it works. I'm guessing the thought process behind it is to get the motor spinning and get some momentum going before it engages the axe, allowing for a faster swing. Less of the swing is used up by the motor starting up under load and thus you should get more speed and power.

Be cool to see it in action.