Big wheels on a heavyweight

[craig_colliass]

Big wheels on a heavyweight

Things seem to be moving on ok with The Saint Mk2 Ive sorted out the hubs modified from car trailer units, and the drive will be my Bosch750 motors with a 19:1 ratio. It looks like the wheels will be about 550 - 600 mm Dia made from HDPE about 15mm thick would that sound about right?

Also if the robot flipped it may get stuck on the face of the wheel, how do I stop this, I know some robots have domes spun from steel like Stinger, is this the best solution? Where would I get them from or made? Thanks guys.

[maddox]

Big wheels on a heavyweight

Other option, think War Chariot style blades on the wheels.

One source of steel domes are LPG tanks. The ends are dome shaped.
Pulveriser used these.

[swanaldo]

Big wheels on a heavyweight

craig i have some 20 to 1 gearboxs if your interested. used with bosch750 in hells teeth3. i will bring them to swindon you can have a look. might be of some use.

[craig_colliass]

Big wheels on a heavyweight

Mario thanks for the idea for the dome, I will look out for some tanks, also old air compressor tanks as they have two domed ends!

Shane please do bring the gear boxes They sound very interesting if not for saint 2 then saint 3! If you know of any Bosch 750 motors anyone has. I need those too, but I know they are like hens teeth at the moment Jonno wanted some a few weeks ago but I think he had to buy new.

[craig_colliass]

Big wheels on a heavyweight

I did some measurements on the Saint regarding the drive

I have 2 Bosch750 motors with a sidewinder speed controller and standard Hawker bateries16Ah I think.

The battery voltage measured at 24.7 volts with no load
The volts going to the motor on full speed measured 22.7 volts
The voltage at the battery terminals under full speed was 23.8volts
I think I am loosing about 1to 1.2 volts through the speed controller is this ok?

[robotwars]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

Thanks guys

The trim thing I don€™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 don€™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 don€™t think another 1.3 volts would make much difference to my fight record!!!!!!!!!!!!!!!

[robotwars]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

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 don€™t think it€™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 don€™t think it will matter to me but I would be interested in people€™s ideas as to where this missing volt has gone!!!

[stu]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

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]

Big wheels on a heavyweight

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

[woody]

Big wheels on a heavyweight

You could try calibrating the Sidewinder ....

QUOTE:-

Different radio systems have slightly different center points and travel ranges. To adjust
the Sidewinder to your radio a small button is located near the Status LED on the circuit
board to activate the radio calibration function. To calibrate the Sidewinder to your radio
systems set all your trims to center and press and hold the button for at least 2 seconds
(remove the front plate to access the button) while the radio is transmitting. The Status
LED will blink rapidly during calibration. Move the radio controls to their full extent
several times. When finished center the controls and press the button again. The
Sidewinder is now calibrated. You can verify proper calibration by observing the motor
LEDs. Both should be off with the controls centered. We recommend you disconnect
any motors from the Sidewinder during calibration.

http://www.robotpower.com/downloads/RobotPower_Sidewinder_quickstart.pdfhttp://www.robotpower.com/downloads/...quickstart.pdf

http://www.robotpower.com/images/sidewinder-bare-top-labels-sm.jpghttp://www.robotpower.com/images/sid...-labels-sm.jpg