First featherweight!

[Mokichi]

Hey everyone, I've been reading around on the forums and now I believe I've got the majority of parts decided on. If you could just quickly have a look over before I confirm the ordering of everything.

So its just a simple wedge robot, which will most likely involve a lifting arm using a car jack, or an actuator. 2WD using Gimson motors (the 14.4v version) to power it. The wheels are 78mm from the Gimson site although I may also get the blue robochallenge wheels (100mm) too.

In terms of batteries I was looking at hooking up two 9.6v NiMH packs in series most probably 3.7Ah, 4.3Ah or 4.6Ah (advice please).

I've got a spare 16.8v drill around which I may be using on the car jack. I've already got the transmitter and receiver. Entire armour and chassis will be HDPE, most likely 10mm-12mm.

The main thing I'm unsure about is speed controllers. I've seen many recommendations around the forums such as electronize and botbitz. I myself was looking at the Sabertooth 2x25 (or the 2x12 is it doesn't need to handle so much current).

Thanks in advance for any help! Dan : )

Also, this bot is most likely not going to be competing or anything, its just something I've always wanted to make (since robot wars is awesome!). Perhaps I'd make and compete with a second FW

[maddox10]

Re: First featherweight!

The Gimson GR01 14.4V want a tad more amps. I would advice a Scorpion XXL, or else the Botbitz controllers.

We use a Gimson GR01 9.6V/Scorpion XL combo, and it moves well, is very controlable, but doesn't have an abundance of power.

I know, a tad more expensive; on the other hand, all the XXL's and XL's Team RCC has in use didn't fail us. Except 1 time, and that was a bit of swarf , after removing the speedo worked again.

Concerning batteries. LiPo batteries ain't as expensive anymore, and the more strick rules don't offset the advantages.

A 4S ( 14.8V) 3000 mAh pack costs between £20 and £45 delivered at your door.

[Mokichi]

Re: First featherweight!

Would the Scorpion XXL offer anything much over a Sabertooth 2X25 though?

From what I can see the sabertooth is the same price but 25A and 50A continouous and peak respectively, 5A higher than the XXL for both. Also there'd be shipping involved for the XXL (and I'd probably want to get the mounting case/fan too!)

[maddox10]

Re: First featherweight!

It seems the XXL has tad higher dependability.

But that could be me.
Team RCC prefers the Robot Power speedo's.
Hannibalito III uses the XXL, Hannibalito 4 the XL.

Kashei and Bullfrog use the Sidewinder .

[plargen]

Re: First featherweight!

if your not going to compete then the sabertooth 2x12 would do just for driving it round at h0me

[Mouldy]

Re: First featherweight!

Used all the above speedos, my review of them all;

Electronise.... relays sticking is a common fault, and control is pretty weak.

Sabertooth.... Everyone I've had seem to forget the centre point during a fight... Don't like any dimension engineering products.

Scorpion XL ... Probably give the best control of all 4, good customer support, very reliable, current handling is a bit low for the price. Nice and small... Would need to make your own surround.

Botbitz tz85a.... Great value for money, reliable, good customer support, good current handling, good all rounder... Would be my choice.

[Gabe01]

Re: First featherweight!

Botbitz tz85a.... Great value for money, reliable, good customer support, good current handling, good all rounder... Would be my choice.


Could you post a link Sir, so I can purchase some

[shakesc]

Re: First featherweight!

Google is your friend

http://www.botbitz.com/

see ESCheap85

[PJ-27]

Re: First featherweight!

Doesn't Cobalt use a Scorpion XXL? The way that thing drives it must be pulling more than 20amps?

[Mokichi]

Re: First featherweight!

A 4S ( 14.8V) 3000 mAh pack costs between £20 and £45 delivered at your door.

In terms of power I was thinking of 19.2V because it's still within the limits of the Gimson and I'd get a fair amount of extra torque and RPM. As for LiPo, I don't particularly mind paying the extra, but just quickly looking on eBay there are so many different makes, any particular recommendations?

Also the botbitz suggestion seems fine, I'm guessing I'd need one per motor or can they control two? Is there anything else I'd need to go with them (a BEC?, from what I've gathered it's just to not require an external battery pack powering the receiver although I have a few external packs already.)

Thanks, Dan

Edit: This Lipo pack for example. Would that be suitable? Also what's the additional ribbon cable attached to it, is it for charging?

[Max]

Re: First featherweight!

I think Calum particularly recommends flightpower lipos

The other lead is for balance charging- you need a charger than can charge lipos. For cheap lipos I recommend the gens ace range on giant shark, it hasn't failed me yet

[PJ-27]

Re: First featherweight!

There's a thread on here somewhere, where I asked a series of questions about Li-Po.

The cells need to remain in 'balance' and this is achieved by using a charger that monitors the voltage of each cell individually. This is done via the extra cable, one lead for each cell and a ground.

[archie2000]

Re: First featherweight!

i have botbitz escheap85s.
looking forward to see the way it drives

[maddox10]

Re: First featherweight!

In terms of power I was thinking of 19.2V because it's still within the limits of the Gimson and I'd get a fair amount of extra torque and RPM. As for LiPo, I don't particularly mind paying the extra, but just quickly looking on eBay there are so many different makes, any particular recommendations?

5S is 18.5V nominal in LiPo, but 21V fully charged.

On recommendations. We have fairly good results with the Turnegy Nanotech in Hannibalito 4. But that's a 3S 3300mAh (11.1V) pack powering the Gimson GR01 9.9V combined with a Scorpion XL.

Also the botbitz suggestion seems fine, I'm guessing I'd need one per motor or can they control two?

Botbitz controlers are single motor controlers, so you'll need 2 .

Is there anything else I'd need to go with them (a BEC?, from what I've gathered it's just to not require an external battery pack powering the receiver although I have a few external packs already.)

A BEC is a battery eliminator circuit.
The main advantage is that you have flat reciever batteries when starting up the machine and realising D'OH , I forgot to turn off the reciever pack.
Moost modern speedo's have a BEC. But I fear it's one of the weak points of the Robot Power products. Those BEC's were designed when 40MHz was the norm, and an old school 40MHz reciever doesn't need as much power as a Dual 2.4GHz Spectrum BR6000. I don't know how the more modern recievers are concerning power, but the older DSM1 type recievers are hungry.

[Mouldy]

Re: First featherweight!

The BEC on the tz85a is 5amp.... wont struggle to power most rx's. Ive used botbitz on dsm1 and dsm2 and it worked fine on both.