Team Thrifty /Fifty Build Diary for Bitza

[PJ-27]

Ohh and I'm sure if we where just to wash all the mud off the robot (it's mostly made from an old lawnmower) it would drop some weight........

[woody]

My advice would be to remove the scoop ...it'll be nothing but trouble.

[PJ-27]

Really?

[woody]

I'm fairly certain that the scoop will bend so much during any impact that it's distortion will probably lift the drive wheels off the floor.

Try dropping it ...scoop down and at an angle..... from knee high onto the ground this will simulate a gentle bump....chest height for rough and tumble and head height for a decent impact.


See what happens.

[PJ-27]

Hhhhmmmm, this had crossed my mind.

Guess I need to think up something!

[PJ-27]

We are almost done (although we have been saying that to ourselves for a while now!).

The robot it now within the weight limit, all of those bugs mentioned earlier have been fixed and some fine tuning has been done.

Ears and front uprights have been added, so not much more we can add to the robot now.

We do have one nasty bug though, where we seem to be about 75% down on power and can't figure out why. Unless we get this sorted before Birmingham then we will be useless in the arena.

[woody]

Hmmm... What was the EXACT setup when everything seemed ok?

What transmitter and receiver do you have?

How is the mixing done? .... I seem to recall some transmitters that have a 50% speed reduction with the onboard mix.

Finally try driving on left and right stick with NO mixing see if that improves the speed.

NOTE: One slow motor would give your bot an awful drive line / curve ...it'll be permanently turning towards the slow motor.

[PJ-27]

The EXACT setup was, two 7.2v NiMH bats in series (with the link separating them), connected in parallel to 2 15amp Electronize ESC (each with a 25amp fuse), these then connected directly to the drill motors. The Tx was the Radio Link T4UE and the old 6 channel Rx. Nothing else was in the chain, no light, mixers, external failsafes, nothing.

The power drop happened after some modifications, which are as follows;
Now the Rx has been changed to the newer 7ch option (since the old one broke). The fuses were increased to 35amp, I added a power light and I neatened up the wiring, which included shortening some sections and lengthening others to make the whole thing sit better.

Other changes included, adding bike tread to the wheels to improve traction and ground clearance, (since the old wheels where smooth and barely stuck out from the chassis) straightened the chassis so that both wheels have equal clearance on both sides of the bot, re-made the motor mounts (old ones came loose) and tweak the wheel mounts so they spin free and smooth with no fouling. I then conditioned the batteries and ran the bot to find the current issue.

One thing that has changed is the new motor mounts grasp the drill motors on the piece of plastic above where the grub screws go in, before the shaft exits the gearbox. They grasp it with downwards and side force. Could this be inhibiting the motor?

We also found that the robot no longer drove straight, one side had a lot more power than the other, whereas before it drove straight and true.

We don't use a mixer, just old fashion tank steer on the 2nd and 3rd channels of the controller.

My initial thought was that the motors had just accumulated crap over time inside the motor casing, but we had taped the air vents at the very start to stop this.

Any ideas?

[woody]

Certainly sounds like a fudged motor.

Connect a battery straight to each motor ..you should be able to notice a difference if one motor is considerably slower.

I doubt that the mount makes any difference...you could of course loosen it temp.

[psychostorm]

My initial thought was that the motors had just accumulated crap over time inside the motor casing, but we had taped the air vents at the very start to stop this.

Any ideas?

Could the motor have over-heated?