Printable View
The other problem alistair is that at 36v they will be pulling nearly 40amps at stall. Thats alot of current and will need a Big speedo to deal with it.
They will also get very hot. Realistically to run golds you will need to use 3amp sanyo cells. These are quite heavy and would weigh 2.85kg.
Another problem with 36vs is a supernova (or replacement) will not charge those batteries.
So perhaps sticking with 24v is a better idea.
Regards
Ian
40 amps at stall is not that much compared to many of the alternative motors available or even a 12v gold which stalls at more than that. If geared correctly I doubt you would have any trouble with a 25 or 30 amp continous rated speedo.
Ian is right in most bots drive trains they will hot, very hot is pushed to hard.
As for needing sanyo C cells to run them this is rubbish, Thuggernought runs 2Ah sub C sanyos on a pair of golds at 24V and we have had no trouble with them and will easily run 2 fights without charging and they are only ever warm after a bout never hot.
The charger issue is a problem but can be over come with 2 18v packs or even 3 12v packs.
The golds in thuggernought are not worked to hard and we are thinking about 30/36v the main problems we have are - new batteries (want matching packs and need a different shape), More weight (We are a bit under but n ot enough) and the fact the electronise speedos are rated to only 24v and I personaly would not like to run them over 30v.
I agree Sam, Ive tested the golds in a bot and on the bench and you definately can run the 24v at 36v. I used the H5 speedcontroller @ 36v on mine. Ive also driven BlacknBlues spinning bar on a 12v gold @ 24v and whilst the motor was very hot the subC NIMH cells were only warm. The only disadvantage of the golds is weight and cost
The other problem alistair is that at 36v they will be pulling nearly 40amps at stall. Thats alot of current and will need a Big speedo to deal with it.
40 amps is piddly. Weve run our 12v winch motors (2.25kg each) in our featherweight Torque 2 Me and they will draw a good 100+amps when we sit on it riding around. We power this all from a single 7AMP DOSS SLA which is 2.6kg. We use an IBC controller and it handles this fine.
In reguard to the gold motors, drill some 8mm vent holes in the case, add some suppression caps if your dont already have them, gear them down more to get the same speed as you would want for on 24v and use 3 x 12v NiMH 3000mAh packs. I dont know much about the H5 controllers, but they sound like they will do fine.
Pushing the limit is all apart of Robot Combat :)
LOL - I dont think youll be getting 200 amps out of a 7Ah SLA
I think you may find that in that circumstance your battery is providing you with more than a little bit of current limiting !
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
We originally though that too Ed, but weve managed to pull 250 amps continous for 1min out of our DOSS 7AMP SLAs on our featherweight spinner Annihilation before the power slowed down.
Weve tested it on two amp meters and both times weve had the 400amp initial start up current then the a drop to 200-250amps continous till the battery drops to 10.6v and our weapon relay shuts off. Funny enough, we thought the batteries would die quite quickly with this type of abuse, but after 4 events with several battles at each, the batteries are still going good.
If your willing to pay $15 Aussie and the P&P, Id gladly send you one for you to do some testing with :)
Surely at 200+ amps for 1 min continuous the little faston terminals would start to melt?
We used to use 4Ah SLAs at 120ish Amps (peak) and after a couple of events the bottom of the batteries had started to sag from the heat they were generating. After a 5 min fight they were too hot to handle.
Im with Ed, I cant believe you are pulling 200+ Amps continuous from such a small battery.
250 amps for 1 min is a discharge rate of 35C on a 7Ah Battery.
To compare like with like, a 35C discharge rate from a fairly standard robot battery like a Hawker Genesis would mean 1 x 16Ah Hawker being capable of delivering 560amps for say 1 min.
Even the 16Ah Hawker Genesis is only rated for 535 Amps for 5 seconds before the voltage drops to below about 7 Volts, and the voltage heads south from there to the point the battery becomes un-usable.
I did have a whole section of the post where taking into account efficiencies of SLA batteries vs rated capacity and Ah ratings I worked out that if you *really* developed 250amps for 60 seconds, you actually exceeded the rated capacity of the battery, and ended up with the terminal voltage of the battery hitting 0v.... and thats before you look at the size of the terminals ! (so I just decided to delete all the maths as it would have just bored people!)
Bottom line is guys, Im sorry, but theres no way a 7Ah battery can supply 250 amps (or 200 for that matter!) (3Kw of power!!!!) for 60 seconds.....
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Well, I want some of those 7Ah batteries because they perform far far better than anything else on the market. Im with Daniel and Ed on this one, its just not possible for a 7Ah SLA to provide 250A for one minute. A really good SLA like a 16Ah Odyssey has a 4C Ah factor of about 40%, this further reduces with higher drains. If we were really generous with your 35C drain and assumed 25% Ah efficiency then your 7Ah battery would only last 25 seconds at 250A. The power dissipated in your battery assuming a typical internal impedance of 28m Ohms would be 1.75kW i.e. meltdown. As Ed suggested, the maths is getting boring.
Paul
Ill try to get some more testing done on them to get some more accurate data for you. Weve tested the same motor and weapon setup with the amp meter on a 15amp SLA and we get the same amperage readings. The terminals are slightly discoloured but they havent melted yet.
Im not sure what voltage it drops down to, but it stays high enough for the relay to keep the solinoid going. Im really tempted on sending one over to you Paul for free just to hopefully prove they these batteries are quite good.
How exactly are you measuring the amps the motor draws? If your winch motors do draw that much power your IBC should have blown long ago.
Ive been wanting to ask that for a while.
Please do send a battery, I can test batteries up to 200A drain and data log the current (+/- 3% accuracy), voltage and temperature from 1mS intervals upwards.
Paul
@Daniel: We used Nicks ampmeter at the Marayong Annihilator when we were going put one of NiMH packs in, but he wanted to check if the motors would draw too much from the NiMHs, Andrew just gave it half throttle and then grabbed the wheel and it shot up over the 100amp mark for about 1-2 sec until he couldnt grip the spinning wheel.
On Annihilation we use a 1000amp analog shunt ampmeter, we use to run it on a 300amp scale but on start up it would just go off the scale, so now we use the 1000amp scale.
I think the IBC takes a bit more because we have a fan mounting on ours and tend to give them a break every now and then when driving them. When Brett did the testing on the older version of the IBC with the crap fet insulator washers, it would take 120amps for 5 secs when the insulators melted before blowing the fets. I dont know how much it could take with the new insulator washers installed.
@Paul: Ill be in Melbourne for RoboWars 2 in just over a week, Ill pick a few more DOSS SLAs up. Will grab and extra for you.
Sounds to me that you need to re-calibrate your amp meter. If you have previously saturated either of those meters then they will no longer give you accurate readings. You should always set the meter to measure a higher reading than what you expect then work your way down to avoid overloading the meter. The best way to test the meter (or measure any current in any circuit) is add a resister of known value in series and measure the voltage accross the resister. Use Ohms law to get a value of the current through the resister (I = V / R). Compare this value against the readings from your amp meter.
I also remember hearing that T2M can run for over 5 min with the 7Ah SLA but when I was running 2 x EV-warriors off a 7Ah SLA the robot was useless after less than a minute and I know for a fact that I was not drawing more than 80A total (I instaled circuit breakers to protect my speedos during testing).
@ Daniel: The 7amp you are using I believe are the Supercheap ones, which we have bought a few and they have been pretty crap, no where near as good as our DOSS SLAs.
The winches seem to draw a lot of amperage quickly when really loaded IE: Person sitting on it. But with the force required in pushing another featherweight and driving itself around, it draws bugger all and has been know to fight 2-3 battles in a row without getting charged(RoboWars 2003, didnt have time to charge).
Do you have HellBringer 3 intact still, as I wouldnt mind lending you a DOSS battery and seeing how long you go with it.
In regards to our amp meter, it could be inaccurate, but weve tested it with RS-550s and its been within 1-2 amps of there specs. About the resistor part, the shunt on the ampmeter is a piece of resistor plating if Im correct, and we just move the wire from one bolt to the another one further or closer depending on which scale we are using on the ampmeter.
Anyway Ill talk to you more about them at RoboWars 2, I think we should give the Gold Motors there thread back and possibly start a DOSS SLA thread :)
Back on the thread...
I recently brought 3 12v gold motors and I wondered what the gear/timing pulleys specs are (looks more like a timing pulley but you never know...). Each of the motors came with a pre-keyed fixing (gear or timing pulley) which may come to be useful...
Regards, Ewan
Ewan just to let you know that you will have to suppose the shaft of the 12v gold motor some way as they have no bearing built in as are available on the 24v versions.
As for gears etc. contact HPC and get a catelogue, I have one and their invaluable.
Regards
Ian
Ewan just to let you know that you will have to suppose the shaft of the 12v gold motor some way as they have no bearing built in as are available on the 24v versions.
As for gears etc. contact HPC and get a catelogue, I have one and their invaluable.
Talk about stating the bloody obvious, that wasnt my question anyway
the HPC catalogue is a good referance but its cheaper to buy from RS or Technobots. See if you can get hold of a couple of old 24v Golds and use their front plates instead of the ones fitted on the 12v ones. Are you running the 12Vs at 24v? Alpha uses MOD1 steel gears, probably abit OTT but theyre the smallest i could get hold of, i could turn them down...but that requires time :P
If your talking about the Timing pulley already on the gold, id reccomend against using that size belt which goes with that pulley. They snap and slip and all sorts. Heat it up and pull it off. Just a suggestion, we learnt with Kitty, and so did the very first Cutlet..
Mr Stu
The plan is Mod 0.8 gears from HPC gears at 3.8:1 ratio (I was quite surprised at the lack of range available from RS infact). The Mod 1 gears are just a tiny bit too big for my chassis which is a shame as they wouldve actually been far cheaper.
See if you can get hold of a couple of old 24v Golds and use their front plates instead of the ones fitted on the 12v ones.
Whats the advantage, it looks pretty similar in construction to the 24v version, although as with the bearing is the face mounting plate different? Im actually on the way to running the 12v at 18v, Im just planning to use 3 4AH 6v SLAs in series, just a nice and simple, cheap solution.
There is a huge difference from using the 12v front plate compared to the 24v front plate. As you and others have said, the 24v one has a Bearing in it - much nicer. I think there ataully mostly the same sizes etc, the 12v has a bush. No bg chnage to physical size, but getting more power, less friction, more life out of batteries, and nicer on the motor overall, the 24v plates are nearly a must have.
Mr Stu
Make sure you have alot of cooling on your motors; overvolting them + 6WD + Very small gear reduction = ALOT of heat! Look at how hot Alphas get and thats running them at there rated voltage.
Out of interest, do you blow air away from the motors or onto them (Or even both :)?) with the fan in alpha?
Thanks for the advise guys
I dont use the fan anymore as it kept breaking (the fins kept snapping off during fights). But it worked by sucking the air from the side sections and blowing them in the direction of the batteries and motors. You might be best to try a strap a couple of computer fans on the motors.
I have also drilled air vents in the motor cases to allow air in. Stiff Breeze also has holes drilled in the motors and hes running a very similar setup to you.
Yeah drilling Air vent holes into the motors is a good idea. Kitty first to do it :proud: LOL! Does make a big difference.
Just make sure you clear out all the bits of metal before you put it back together or big problems arise.
Mr Stu
You will have to keep a VERY close eye on the motors heating up, you would probably want to mount them in ali or something to act as a heat sink with the fan cooling that. PloughBots lifter motor gets almost red hot. and that isnt running all the time. It sends paper brown and can nearly set tissue on fire after a fight so be warned and be careful!
At this point I should point out that we turned down the motor casing to save weight and this disturbed the magnetic circuit and resulted in poor efficiency causing the motor draw more current and to heat up more.
I assume adding holes would casue a similar effect and not to mention the increased EMI casuing more http://www.x2y.com/cube/x2y.nsf/1/07...72604FDCM.pdf>
I have not noticed any problems, but i have just drilled one single hole which is inline with the joint in the magnets (therefore in theory if there is any effect it should be equal). The hole is as far away from the magnets as possible (level with the brushes). There may be a small drop in efficiency but its not been noticable.
Cant say there are any EMI problems with Kitty with all the holes drilled in the motor. But know in other cases when you do the same with motors, things happen. So yeah something to watch as Mark said.
Mr Stu
PS - Dogs looking cool Mark!
I think Ill just use a big lump of ali milled out to accept the motor body for both mounting and heat conduction, shouldnt cause any efficiancy or EMI problems.
So far Ive just modded the leads to 6mm2 silicone cable which is nice and beefy compared to the weedy cables which came with the motors.
Ill hopefully put a gold mod page on my site soon. Ill try and get my hands on some 24v golds asap
sounds kool. would a steel ring aroung the motor casing increase the power of golds?
Has any1 tryed this?
I have thought about that as well, if i get time ill give it ago for next event. I know drill motors have a extra steel sleve that improves the performance. I suppose it depends how effective the casing already is and wether it will make much differance.
The extra steel sleeve on the drill motors is actually to be slid over the ventilation holes during manufacture so no crap or swaff goes inside the motor, its also handy for when you have to drill around your motors :)
The steel ring can enhance the torque of the motor, by containing the magnetic field inside the can.
Easy way to see if the can is thick enough is to use a thin piece of steel. If it sticks to the can, the magnetic field is not contained entirely, ans therefor loses a little force. The stronger the attraction on the outside of the can, the worse it is.
Ahh, does that decrease the speed though? I have been running a small motor in my RC Plane and it says to remove the ring but it doesnt say why. (I guessed that having one on increases the torque, and so would it decrease the speed)
Is this what happens?
Grant, looking at it logically, if the magnetic field is reduced then i would say that the motors back EMF is reduced and thus the motor will run faster to further increase the back EMF until it balances out.
Hi Ewan ,If you are overvolting 12v gold motors they wont get hot, theyll get VERY hot.
But then it does depend on the gearing,current limit (if any,slas should be ok),and the way you drive it.
Stiff breeze 12v golds at 19.2v (using sub-c nicads) with a 40amp current limit,5:1 gearing and 80mm diameter wheels.
So far Ive metled the armature insulation and had the armature spindles come loose.But im blaming Toms driving for that! :)
:)GORD
LOL! AWWW!!!! OH Dear!
Gord - how could you. LOL.
Mr Stu
easy, by over volting them:)