Speedo control cutoff problem

[Chris Elworthy]

Alright lads,

I'm new back to racing and am experiencing some rather strange problems with my speedo or possibly motor. I'm using the Speed Passion GT2.0 speedo with Thunder Power 7.5 motor in my Losi 22.
What is happening is, around 4 minutes into the race the power from the motor will cut and the buggy will grind to a halt, the steering however is not effected. If you then switch the speedo off then on again the car is back to normal as it was before the cut. The speed control has recently been returned from Schumacher as I thought it was faulty earlier (turned out to be a faulty transmitter) so has been tested and is supposedly fine.
Other observations are that the fan had stopped working the first time I noticed the cut in Power and hasn't worked since, this shouldn't be too much of a problem in a 2wd though.
I've been back to the setup box and reduced the voltage cutoff to 2.8 and alsO tried a reciever capacitor but no joy.

Has anybody an idea of what could be happening? Is it possible the motor could be damaged causing the issue? I doubt it matters but the car is being powered by Orion 90c 5500 Lipo's which are brand new.

Has anybody got an idea of what may be the issue? Its a really frustrating problem as you only know you have it when it's too late



Chris

[mattr]

Three things.
What temps are you actually seeing in the speedo. Just saying "it should be ok in a 2wd" doesn't really cut it!! One of the guys racing yesterday has had some overheating problems in his 210. (Fanless ESC) And i've had one hot enough to make me think twice about touching it (210 again)

And what servo are you using? If its a Savöx, they can do funny things to the BEC/ESC as the battery discharges! i.e. high current drain at certain points on the track can make it brown out as the voltage dips, even tho the battery is still good to go. A glitch buster can fix this.

Also, check the motor wires are soldered properly, i had an intermittent problem like this due to a badly soldered motor connector, once it got hot it cut out and stopped working properly, by the time i got to the car, it had cooled down and started working again. Until the solder joint actually separated properly!

[Chris Elworthy]

I haven't been able to check the accurate temperature of the speedo but it doesn't feel overly hot to me. It does seem similar to a voltage problem as it seems to happen as I open the throttle fully at the start of the straight. I borrowed a glitch buster to try yesterday but didnt seem to work, which reciever port do I use for the booster? I'm using a Sanwa 40 MHz recover which has 2 spare ports after TX and RX, one AUX and another.

It's strange how the fan stopped working so soon, maybe I will remove it as it may improve air flow to the speedo.

Chris

[Chris Elworthy]

Sorry, forgot to mention I'm using a low profile Futaba 9550 servo.

Chris

[dodgydiy]

what cells are you useing and what is the speed controls cut off voltage set to?? if you are on nimh you dont want any cutoff voltage set, on lipo check its on 3V per cell, have known problems with cutoff set at 3.2 volt per cell causing car to stop when accelerating out of corners, lot depends on battery really. also connectors, have personally had problems with a bad connector causing speed control to cut to voltage protection, if you are using deans connectors keep an eye on the spring tabs, they can go flat causing the connector to become loose

[mattr]

No idea then :/

Other than checking all the wires.

[dodgydiy]

sorry didnt read that very well, you do say you are using lipo and have set the cutoff voltage, drop a tooth on your gearing and replace the fan, if that stopped at about the same time

[Chris Elworthy]

Thanks for the input lads. I'm using corally connectors but they were unsoldered from an old speed control so are a little worn. I shall replace these with new Corally's and resolder the tabs on the motor. The car is doing exactly that, it cuts under hard acceleration, usually at the beginning of the straight under hard acceleration out of a 90 degree corner. I had the cutoff voltage at 3.2 but dropped it to 2.8, how low can I safely go? The car is running 1 tooth lower than the recommended gearing as it was running on a twisty track. Additionally the track was wet so I was being far smooths on the gas but still the problem occurred.

Finally, does this sound more like a glitch or incorrect speedo setup over an actual faulty speedo? It's just that te speedo has only just been returned from Schumacher and I'd hate to have to send it back again.


Chris

[mattr]

Can you reset the speedo back to factory settings, then start setting it up again from scratch.
Doesn't sound like a battery issue, i use the same type (but saddle) and get nearer quarter of an hours running (with a 3.2V cut off).
And FWIW, 2.8V is probably too low.

I'm still thinking either a loose or damaged wire, or a brown out (how is the servo? New, old....... knackered?)

[MattW]

I'd actually suggest switching the voltage cut off and doing a run. Obviously be certain not to run for too long, but just to see if it makes a difference.

[RudolfXC]

I'd actually suggest switching the voltage cut off and doing a run. Obviously be certain not to run for too long, but just to see if it makes a difference.


This will also turn off the motor cut-off which could be the cause of the problem due to some form of incompatibility.

[Chris Elworthy]

Thanks a lot lads, ive not had chance to try the car yet but earlier my mate spoke to Stuart Wood and he said that the Speed Passion drivers often turn off Voltage cutoff as it can be too sensitive. Obviously i will have to make sure I don't run the car for too long but if it will last the 5-6 minutes it will do me. I will try to get on the track tomorrow and report back.

Cheers lads,

Chris

[morpheus2010]

Someone at our club ( Southport ) had his car cutting out on hard acceleration after ~4 mins. Eventually dropped a couple of teeth on his pinion and no more cutting out.

Could have been over geared and hi-current draw caused a voltage drop perhaps enough to trip the ESC cut out.

[Chris Elworthy]

Hi lads,

Sorry for the slow Replies. I'm happy to say that the cutting out problem has now been solved simply due to turning Overheat protectecion 'off'
This is something that the team drivers do as the cutoff temperature is far too low so cuts out. We ran an 8 minute A-final at Bury Metro on Sunday and had no problems at all, the motor naturally was a little warmer than after a 5 minute race but the speedo temperature was no cause for concearn.

Morpheus, I would suggest that your mate from Southport tries this with his previous gearing, you need to be able to be flexible with you're gearing to tune it to the track not be restricted due to cutout issues.

Hope this helps.


Chris