Big wheels on a heavyweight

**robotwars** · 15th January 2008, 10:34

both myself with the new ripper, and beast are now using sidewinder speed controllers and have both thought that we have lost some speed due to the speed controller, compared to the roboteQ.

This might explain it. I am planning on putting the roboteQ in ripper for swindon and am going to compare it.

Interesting what you say though !

John

**big_nipper** · 15th January 2008, 11:58

While its true there will be some voltage drop in the speed controllers, even at full speed (unloaded) the volt drop from a sidewinder or robotec should be way less than 0.1 volts. Its more likely something else. The most common is that you are not using the full range of the RC signal, could also be very thin wiring / bad contacts. The first is easy to check. Put the transmitter stick at full speed, then adjust the trims, if it speeds up then youve solved your problem. The other common reason of driving slow in an arena is that you are hitting the speed controllers current limit. Be careful when adjusting the sidewinders current limit as too far can turn it off.

**mark_m** · 15th January 2008, 12:04

Were your voltage measurements at the motor terminals and the battery terminals or at the input and output to the speed controller?
Lets assume that your no load current for your drive is a total of 30A (is this reasonable?) then this would mean that if theres a 1 volt drop across the whole system (minus motor and battery) your system has a resistance of 33milliohms.
That seems reasonable to me.

**craig_colliass** · 15th January 2008, 12:49

Thanks guys

The trim thing I donâ‚¬â„¢t think this is a problem as the radio is Spectrum and I have adjusted the travel to elevator aileron to125%. But I will do the test tonight and will keep you posted.
The readings were taken at the battery terminals, and motor readings taken at the connector plugs fitted to the motor the nearest possible point to the motors. The wires are those supplied by the motor manufacturers and the Sidewinder tails everything else is the Technobots big cable 16mm stuff.

I would like to say that I donâ‚¬â„¢t have a big problem with the Sidewinder performance, it works well, I have had one of my Bosch motor drive chain seize up and the sidewinder was un harmed, even if the Bosch was un touchable for quarter of an hour because of the extreme heat this event generated. I can live with 22.7volts at the motors if that is reasonable I donâ‚¬â„¢t think another 1.3 volts would make much difference to my fight record!!!!!!!!!!!!!!!

**robotwars** · 15th January 2008, 12:55

Hiya,

Yeah i just wanted to add..... we dont have a problem... it was just something that we noticed, and coincidenly said to each other.

We may be completely wrong. The side winder is a nice small it of kit!!

John

**craig_colliass** · 15th January 2008, 14:34

Yep

I just done the tests and Battery with no load was 25 volts, battery under load is 24.1 volts, and input to motor is 23.1 volts at the plug.

I also tested the volts under load at the speed controller tails they were
24.1 volts input
23.1 volts output
So I donâ‚¬â„¢t think itâ‚¬â„¢s the resistance in the rest of the circuit, has any one measured the input to output volts, on their speed controllers to see if this volt drop is there on all speed controllers. I donâ‚¬â„¢t think it will matter to me but I would be interested in peopleâ‚¬â„¢s ideas as to where this missing volt has gone!!!

**stu** · 15th January 2008, 14:40

I think its something to do with the spectrum if im honest. I noticed a change in speed when using the specktrum... i think i played with the end points and it was ok... so i think Jonno and John Lear just need to read some books and setup teir specktrums and sidewinder current/slew limits correctly.... LOL

Mr Stu

**typhoon_driver** · 15th January 2008, 14:46

It probably is the spektrum. I had similar problems in Hive at the UK champs. Although mine were somewhat worse.

24V going into the speedos but only a max of 11v coming out to the motors.

Got home, took the spektrum to its extremes with the travel and bingo problem sorted.

This is one of the major reasons I dont like the spektrum. I only have one around in case my 40meg stuff gets damaged.

**robotwars** · 15th January 2008, 14:48

ive got no idea.... it works so ill leave it alone !

Someone did tellme about the speckrum causing a reduction.... it might have been stu.... i did mess about with the settings but gave up, as i didnt want to mess it up, and it didnt appear to make any difference.

When I put the roboteQ in over the next week ill have to measure the voltage as i am curious now.

I bet the 1 volt is being lost, it is being used to power the little hampster on its wheel inside !!

john