First Time Bot Builder/Buyer

This is a rough price breakdown for my bot - its a 4WD invertible (I hope!) rammer so quite similar to what youre after:

Motors - 4 x 9.6V cordless drill motors - £40
Batteries - 4 x 7.2V Nicad packs - £20
Wheels - 4 x 75mm blue wheels - £22 (Although Id strongly recommend using 100mm blue wheels if you wanna be invertible - I managed it with the 75mm ones but vertical space is tight! Main bot chassis is only 50mm high!)
Speedos - 2 x Electronize 30A with external relays - £100 (15A microprocessor Electronizes are a cheaper option but only by about a tenner each)
Radio gear - 6ch Skysport - £120 (Technobots 4ch kit would be better though, and only £40)

Then theres the things you forget about at first:

Battery chargers for nicads - 2 x fastcharge units - £40
Miscellaneous nuts/bolts/screws etc - Could well possibly be up to £30 depending on how much you use.

So, going by the cheaper options Ive listed, youre looking at £255 give or take a bit, not including materials for chassis etc or any form of weapon. Thats the cheaper end of the scale anyway...... :)

EDIT: Forgot about things like a removeable link, power light, failsafes, mixer etc - approx £35-£40 on top of that

(Message edited by K_C_R on April 25, 2007)

Jamie, if you are going to spend £120 on radio gear. You may as well get a Spektrum for an extra £30, we have 2 they are brill. Unless its too late.

Spektrums werent around in 2003 unfortunately :)

£120 was one of the cheaper quotes I got for the full kit; receiver, tx and rx nicads, charger and servos etc (one greedy model shop were trying to flog it for £170 - no wonder they went out of business)
It was also before the 6EXA came out, back when the Skysport 6 was the main product, hence why it still cost a lot

ABS Roller from car boot £2 = 4 off 100mm dia wheels
3/8 UNF Deep Manifold Brass Nuts from your local motor factor another £2.

So for under a £5 you could get four wheels thatll fit on drill gearboxes.

As good quality wheels that arent likely to break? Questionable.

Questionable.
Yes ...Ive not yet tested mine ...but to me they look O.K. :).

http://shop.bodybuildingforyou.com/Images/ASOT/ab-slider.jpghttp://shop.bodybuildingforyou.com/I.../ab-slider.jpg

so would that gimson kit do me with 4 wheels instead of 2 and 4 motors instead of 2 then? would that speed controller in the kit handle the 4 motors?

then i would need radio gear, batteries, chassis, fixing (bolts,screws etc),then armor.

what else?

I would suggest that to handle four drills the Sabertooth controller should be mounted securely to an aluminum block or extrusion or similar for additional heat sinking and a fan directed upon the board (you could run a small fan from your main battery or receiver power). Also avoid stalls. But up to 14.4v that should be fine even for four drills.

I have used one un-heatsunk unit with two 9.6v drills at 18v (100mm wheels) for around five minutes without any problems beyond a hot controller. Its just a case of taking all the precautions you can.

how many 7.2V NICAD (2300mAh) batteries would i need to power the 4 motors or should i go with drill batteries instead of the rc car packs? drill batteries are like half the price too:p

(Message edited by xtreme on April 26, 2007)

This looks like an excellent option http://cgi.ebay.co.uk/Radio-Control-Battery-Pack-12V-3700mAh-SC-NiMH-Compact_W0QQitemZ300103587339QQihZ020QQcategoryZ34 063QQssPageNameZWDVWQQrdZ1QQcmdZViewItemhttp://cgi.ebay.co.uk/Radio-Control-...MH-Compact_W0Q QitemZ300103587339QQihZ020QQcategoryZ34063QQssPage NameZWDVWQQrdZ1QQcmdZViewItem

And remember youll need a charger suitable for whatever pack(s) you choose

ill get a cpu fan and heatsink that should work right? if i got it cooled how long will i be able to run it for?

would that one battery power 4 motors?

Hehe look i dont wanna be this simple. ohh i asked him, he knows nothing about the radio gear or weights. there using upsidedown wheel barrows as bodies. http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&ih=020&sspagename=STRK%3AME WA%3AIT&viewitem=&item=300104293276&rd=1&rd=1http://cgi.ebay.co.uk/ws/eBayISAPI.d...STRK%3AMEWA%3A IT&viewitem=&item=300104293276&rd=1&rd=1

A substantial aluminum would be a good bet, and also any general cooling fan should do. Places like maplin should have suitable stocks, for example http://www.maplin.co.uk/Module.aspx?ModuleNo=32006&criteria=fan&doy=26m4http://www.maplin.co.uk/Module.aspx?...a=fan&doy=26m4 which is nice and compact for a potentially small machine also technobots have a cheap offering if youre going to be buying things from there http://www.technobots.co.uk/index.html?lang=en-uk&target=d538.htmlhttp://www.technobots.co.uk/index.ht...rget=d538.html

Yup, that battery would be fine, though you could do with a spare so you can charge one while the others in the robot. Those wheelbarrows look like ancient relics hehe. The windscreen wipers and batteries probably arent worth the £50 :)

better get to bed up at 6 :p james baker is emailing me about some second hand stuff so ill drop you a message see what ill need for my build gimson and ebay should have it all. thanks for the helpful info tonight ill be back bugging you again :p Cheers

(Message edited by xtreme on April 26, 2007)

No problem, I best be off too, oh the joys of early mornings hehe

I dont want to pee on anyones chips but I would be wary of relying on both a large heatsink and fan combination to keep a speed controller cool.

What you have to remember is that in a battle the motors could be be slammed from full forward to reverse and everywhere in between. A drill motor can draw relatively large currents and these will happily blow up a speed controller with a low current handling capability.

I dont want to get into a debate with anyone and this is not meant to be offensive to anyone. Just stating a few facts.

I am sure that it could quite happily be implemented but it will require a fair bit of thought to make sure you get the required air flow and keep it cool.

I think these speedos have prety good current limiting, not too sure on how well but ewans done a few tests and they seem to work well lie that.

you should ask mark lumb about his opinion of the sabretooth.
in my opinion, heatsinking it in the way described is pointless, as you are heatsinking the plastic case, which is never effecient anyway. secondly, the current limiter is a safety feature, and cannot be relied upon once it is hit once, to be reliable the next time.

On 2 9.6v motors at 9.6v or lower, maybe the sabretooth is ok, if you resin it to stop all the heatsinks falling off, but for 2 pairs in parallel??? No, I dont think it will be enough.

go with the 2 electronize from technobots or the 1 scorpion (scorpions are £85 from me) for this application I think, or 2 sabretooth in resin.

I have yet to have a problem with my 15A electronize. Even stalled two gold motors on 24v with them and they got a bit warm but didnt blow

James the base piece is aluminium and can be mounted to for additional heat sinking, not plastic.

Although the unit is small it all depends how you set this controller up in your machine. I have full faith that without mechanical problems arising etc. One cooled and heat sunk unit could handle for drills (pairs in parallel). Shame I cant test this myself practically at the moment.

The effect that 4wd has in this case not been looked at carefully here: when you run four drills with four powered wheels, each wheel will typically have less traction and be easier spun, and though the skid steer pattern can produce brief current surges, the overall train wont consume all that more current than two drills taking the majority of the drive load.

At the end of the day its all up to Tom as to what he thinks best :)

Gary, electronize are great (especially 15A CPU ones) but once youve uses complete solid state speedos the relay delay is impossible. Ive never blown up an electronize from giving it too much current, so you cant go wrong with them for a starter.

I never notice the delay, wonder if thats just my bad driving :)

I would like to upgrade one day but if it aint broke then dont fix it!

ehhh so i dont know whats my best option now. what if i mounted a fan over the speed controller and 2 in the body armor i dont wanna waste a speed controller. but i dont wanna spend alot more cash if it will be ok.

if i had to go with 2 speed controllers which ones would i use for the 9.6v Drill Motors?

could somthing like this work? http://cgi.ebay.co.uk/Mtroniks-VIPER-Marine-15-15A-speed-controller-ESC_W0QQitemZ290106340077QQihZ019QQcategoryZ2564QQ ssPageNameZWDVWQQrdZ1QQcmdZViewItemhttp://cgi.ebay.co.uk/Mtroniks-VIPER...r-ESC_W0QQitem Z290106340077QQihZ019QQcategoryZ2564QQssPageNameZW DVWQQrdZ1QQcmdZViewItem

Tom, sorry to complicate your decision.

If I were you I would go with a solution that has been used a huge number of times with no problems.

Go technobots and look at getting 2 RC speed control 30A with External Relays (part number 1500-022).

Yes it will cost you more initially but its usually better to spend the cash now and not spend twice as much later with blown speedos. Or you could see if anyone has any for sale second hand.

These should be able to happily control your motors without bother. I am always wary of extreme cooling methods ie lots of fans etc as your robot is relying on a small piece of spinning plastic.

Just my 2 cents.

ok cheers ill see what james baker has for sale. any more ideas for speed controllers anyone?

(Message edited by xtreme on April 26, 2007)

would 2 of those those mtroniks viper 15s do the job? or the viper 20s?

ill return your email monday or tuesday tom, in the mean time, dont buy anything, you will waste your money on things weve already blown up.

btw Ewan, I know how the sabretooth works, Ive had one in bits already for extensive testing, and in 3 different robots, but thanks for the info. I stand by my earlier info. :)

Keep youre hat on James. If its the transfer material youre referring to you mightve underestimated it. ...

(Message edited by ewan on April 26, 2007)

?
sigh

ok? i just want a cheap and cheerful rambot that i can kill my friends rc cars with till i can get to an event

Tom, the Viper 15s or 20s would probably work (if youre going 4WD then lean towards the 20s) but from having a quick look through the specs, the highest input voltage you can use is 12V, which means if you ever want to upgrade to, say, 18V or 24V, youd have to get new speedos. (Just as a comparison, the Electronize take up to 24V input)

As Jamie said. The Mtroniks speedos do work well aslong as you dont run them any higher than 12v.
Not too sure on the price of electronize lately, but ive still got some in an old robot that ive had for 4 years on gold motors and theyve never got warm. A very reliable controller. As others have said, there is a tiny delay as they use relays, but unless youve driven a robot with a very expensive speedo you wont be able to tell the difference its that small of a delay.

i got tiny rams off my mate dave today. i was testing it out using a small compressor but wasnt that powerful ill youtube the vids and post em later might just use it as a can crusher or somthing. plus its got a leak in the airline connectors just couldnt be bothered sealing it :p

(Message edited by xtreme on April 27, 2007)

got a little vid of the rams in action now but im not impressed http://www.youtube.com/watch?v=6DWR015pxVUhttp://www.youtube.com/watch?v=6DWR015pxVU
dont know what im going to use as a air tank and how im going to connect it and refill it.

for a featherweight weapon it it is very weak indeed. Id look for a different setup if I were you.

mind you, setups like these are great to make test configurations.

so how was the weekend for you all?