New Heavy

Taken the plunge, i know i know, i should probably do a feather first but what the hay its all for fun and if it gets destroyed at least i will find the weak points !

I have been lurking and learning, asked the odd question, given away 13 electric wheel chairs and motor kits for free to forum members so not totally new.

I picked up Hardox and Daveimi old shell and sort of merged them !

Shell - Done ( no paint yet)
Weapon - 80% done
Drive Train 60% complete
Wiring Harness 85% complete
Wheels - Ready just waiting on motors.
ESC on its way but harness ready to receive it


Well within weight limit at 77kg, so Armour will be my last task once weighed...
( how is it weighed at a live event & how close do you skirt to 110kg...)

now my weak point .... i really hate electrics.. but i can do it..

Can some one translate this for me into suitable battery packs and how many i need based on your experience?

I am limited to 45v max, but up to 60 amps per channel output.

Spinner weapon is 17 kilos, was thinking hi amp starter solenoid for it perhaps ?

i have 4x 350w motors or 2x 800w to choose from.

● 6 – 18 cells NiMH or NiCd battery.
● 3 – 6 cells LiPo or Li*Ion battery.
● 10V – 45V sealed lead acid battery.
● 10V – 45V power supply (​ Must be in parallel with a battery with same voltage​


Opinions and helpful direction welcome.

Quote:

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Originally Posted by katch

Taken the plunge, i know i know, i should probably do a feather first but what the hay its all for fun and if it gets destroyed at least i will find the weak points !

I have been lurking and learning, asked the odd question, given away 13 electric wheel chairs and motor kits for free to forum members so not totally new.

I picked up Hardox and Daveimi old shell and sort of merged them !

Shell - Done ( no paint yet)
Weapon - 80% done
Drive Train 60% complete
Wiring Harness 85% complete
Wheels - Ready just waiting on motors.
ESC on its way but harness ready to receive it


Well within weight limit at 77kg, so Armour will be my last task once weighed...
( how is it weighed at a live event & how close do you skirt to 110kg...)

now my weak point .... i really hate electrics.. but i can do it..

Can some one translate this for me into suitable battery packs and how many i need based on your experience?

I am limited to 45v max, but up to 60 amps per channel output.

Spinner weapon is 17 kilos, was thinking hi amp starter solenoid for it perhaps ?

i have 4x 350w motors or 2x 800w to choose from.

● 6 – 18 cells NiMH or NiCd battery.
● 3 – 6 cells LiPo or Li*Ion battery.
● 10V – 45V sealed lead acid battery.
● 10V – 45V power supply (​ Must be in parallel with a battery with same voltage​


Opinions and helpful direction welcome.

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I guess the weapon is a spinner?
Would really help if you could give us the MoI of it (or at least the rough shape and diameter), since weight distribution is at least as, if not even more important than the pure weight to know how it will behave.

The Weapon is a 500mm solid hardox Z shape thats been stretched slightly, running on 2x 35mm ID bearings. Its currently 19 grams out of balance, but it will be balanced after the sprockets are fitted to it.

MOI ?

MoI = Moment of Inertia.
Or: how much do i need to push to get this thing rotating?
In that, the diameter and mass distribution along this diameter are the factors. For every single bit of mass it's calculated per m*r², so the radius (and weight distribution) is more important than the actual mass to see how fast a spinner will spin up, how much energy it can store etc.
That's why a spoked disc of the same weight and at the same speed can store more energy than a solid disc or bar, because more of the weight is further away from the axis.
That's also why i'm always a bit irritated by people giving the weight of the spinner as only factor.

But apart from having some physics knowledge, i am a noob to robot building, so i'll let the actual answers for other, more experienced guys. Just thought this might be an upcoming question anyway, and wanted to make it easier for those who actually can answer to this thread once they do so ;)

Come here often :)

Is it running gear for the weapon your stuck with? Are you gonna go with brushless or brushed?

Sorted now, got some expert advise and a lot of guidance from a really decent Roboteer !!

I can guarantee most teams will not have calculated the MOI or inertia of their weapons. Most teams just ball-park their system against previous known setups, both ones that worked and didn't.
I'd take the mass of your weapon and diameter and find some robots with similar weapons and see what they use as motors. If you can't afford or have the weight for what they use then increase the ratio so it will spin slower and use a smaller motor.

As for your motors and batteries, they need to be worked out together. You need to guess how much capacity you need and what voltage all your motors run at, be it 24V, 36V or 48V. Again, look at other robot setups, take something that worked and then adjust it to suit your needs.

PP3D has a MOI on it's disc of 1.946896539 kgm^2. With a rotational velocity of 2500rpm or 261.7993875 rad/s that results in a kinetic energy of just over 66kJ. Those figures for MOI came from CAD. Of course these are perfect world with no resistance figures. The actual KE is probably a good 10% lower but that doesn't sound as impressive for the cameras.

If you don't have access to CAD to calculate your MOI you can use the team cosmos calculator to do it for you (with a few assumptions about shapes etc). http://www.teamcosmos.com/ke/ke.shtml

It is in imperial units but converting your dimensions to inches isn't difficult

666 hectajoules sounds even "heavier"....

With the help of a local bot builder who has competed already, i've picked up some more ideas and removed some poor ideas he shared willingly..

Ignoring calculations, i'm just not clearly not clever enough for that, i'm going mechanic style, "trial and error".

Test drive soon i hope ! No weapon, weighted for a battery load test. See how it goes or doesn't..

Update,

I went to a live event and ended up helping repair and load / unload make safe and arm the Bots. I was offered to drive, but the setup on the controller really didn't make it easy for me so i passed after a quick go.

I would recommend getting yourself down to a live event and seeing what "really" happens are what you think might be going on at an event.

My own bot has benefited from this day with ring side seats and pit work. I've changed a few failure points, and now seen a working set up. So on return i have a lot of enthusiasm and got my own HW up and running and tested for the drive train.

Its works, its starts, stops, and most importantly steers !!

The Bot cuts out with loss of signal and Safety Link does exactly what it should but won't fall out.

I have tested several areas i had concerns over an fixed a couple unexpected weakneses.

Now its time to start the weapon build and get testing.

I shall pop some images up as soon as i figure out a place to host.

Attachment 6707Attachment 6708

Okay,

So its mocked up with a removable drive train via 8 bolts. The whole thing comes out in one piece for easy maintenance. Running on Pallet truck heavy duty alloy wheels.

The batteries are spare motorcycle 12v i had lying around, but i have lipos ready to go when i am ready.

The drive is 2x scooter gearbox 24v left and right, with a mixer speed controller. Works really well and really easy to control.

Looking good! What's the weapon?

Oh sorry i forgot that !!

Its a donated part from Hardox, its on loan between both my bots, i'm using this as a learning curve so its most likely going home in a bin liner !!

Attachment 6709

In the pictures you will notice nothing is parallel or square, thats all been sorted now, but was simply because everything was put in with only 2 fixings and no structure really in place while i finalised my locations for parts etc... The first test drive it all moved and twisted.

This is so awesome :) Soooo glad it went to a good home!

Ok so its been a very long year for me.. House fire has taken over all my spare time since june july, only 2 weeks i'll be in my new house and i can concentrate on this bot.

I was going to post up some new pictures, but there isn't much thats change, but here is the revise weapon, coming in at

16kilos.. with a chain drive rated for 9,000lbs of strain..... Attachment 7440

Glad to hear your back :), give me a shout we will have to catch up one weekend

Gladly mate, i'll pop on up to yours, i have that 2nd chassis still and plans for it look promising ;)

This chassis i'll take to a live event with you if your up for it and see what that quad blade does to itself !

Quote:

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Originally Posted by ACE Robotics

Glad to hear your back :), give me a shout we will have to catch up one weekend

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Figured out my esc can be mixed on its board so tank steering by 2 stalks separately now works on dx6i .

Having been playing this weekend sort of finding time to figure stuff out.

36v the bot is much more lively so on lipo I think it will be just right

Got sparks on esc solved when connecting battery that was really easy.

Blew up the down voltage converter for receiver during the learning process lol

so onto weapon drive next..

Thinking of Binning my lem 48v off ... maybe using 2x or 3x 12dc motors

How did you stop the sparking when connecting the ESC to
the battery ? as I have a similar problem and the same ESC too.

The sparking when linking up is the capacitators charging.

The way to avoid that is to use a "precharge" link/lead , in short, you "precharge" the capacitators trough a resistor limiting the power that will flow before you put in the main link.

These should help

https://hobbyking.com/en_us/xt90-s-a...___store=en_us

Quote:

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Originally Posted by team death

How did you stop the sparking when connecting the ESC to
the battery ? as I have a similar problem and the same ESC too.

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Basically I use a 7.2v battery pack to charge the capacitor like Maddox said i then disconnect and attach the 3x 12v packs as it doesn't
Discharge

Okay so today was 36v 34amps 3 batteries lead acid in sequence. ...

Ran fine with me stood on it no change to speed or acceleration at 1/4 throttle so 95 kilos doesn't impact it at all..

I Cut out integrated switch on esc to power esc with its' own on/off switch makes charging capacitors easier.

Receiver now runs from esc which didn't Realise was there.. note to self..read manual Chris...

Rammed it full speed into pavement and it shook it off dozen times in a row. Esc fans happy for now and nothing fell off lol

Needs larger rolling diameter wheels next as its overgeared

That is one decent ESC! All that power, durability and chep price! Might order a couple myself.

Team death / myself and kaizen are using them. I think gearing is the key to get the best out of them but I'm over volting wheel chair motors at the moment.. ive tested the my1020 24v too at they like it...

Yet to be battle tested mind ..

As I noted in Kaizen's build thread, I'll probably end up adding a few passive heatsinks to mine to add a extra layer of cooling (there is definitely enough space underneath the fans to allow this) but certainly sounds promising at the moment as is. Reckon it'll make it to any events this year?

I'm happy with drive, a touch more speed be better but larger wheels I think is all that's needed.

weapon and lipo are next

so April Manchester is not out the question... but mines a spinner so prob not allowed... not sure of rules

Last year Extreme Robots did allow spinners but they had to be mechanically limited to 125mph I think and subject to pre-approval. Worth asking the event organisers directly I think ;)