kengentry5000

My Feedback: (2)

Hi All,

I installed a Hitec 9745 Ultra torque throttle servo on my Firehammer a few months ago. I noticed it will "twitch" back and forth some while the car is sitting idle with engine running. It's not enough to blip the carb but it does concern me a little.

My bashing area is right next to a commercial airport. I wondered if stray RF interference from the airport could be the cause.

Then I saw where one large scale RC reseller recommended a PCM radio over an FM radio. The impression I got from the recommendation was that the vehicle ignition system could possibly cause glitching. My Firehammer has (to my knowledge) the original spark plug from Duratrax. I was told by my local hobby shop that I should buy the "hobby grade" spark plug because it reduces interference with the radio equipment.

Any ideas on what would make this servo twitch? Any suggestions on how to make it stop?

Thanks,
Ken

icecreamslick

My Feedback: (9)

My throttle servo did the same thing a while after I had my MB. I turned out to be the failesafe. Once I removed it, the problem was solved, so I bought a new (better) one the next day. I would suggest that you take the failsafe off and see if you still have the same problem.

Good Luck!

p113

i have the hitec servos and every so often get throttle gliching usually the same as yours just sort of shacking but this weekend it gliched enough to change the carb and accelerater into a wtery ditch lol usually no probs though ive though of getting a different spark plug top but the gliching dosent happen to offten touch wood

radio_controlled_mad

i have pcm radio gear and digi servos and still get glitching - i think its something to do with charge from the battery - or so the guy said the model shop - seems to happen more after a recharge.could also be interferance from engine electrics!! but thinkin on i have two of the same servos running hydro but i only get twitching in the throttle servo - throttle rod may conduct interference!!!

p113

but theres a plstic servo horn to so it coulnt conduct electricity my reciver has a built in failsafe

Mad Wax

Buy a new radio now (had 40mhz FM) I ignored it and caused £120 worth of damage. You could also buy a shielded spark cap.

radio_controlled_mad

my receiver is built in f/s also - my servo horns are held in by alan bolts - sometimes when i start messing round with a alen key on the servo they glitch like mad - cant think of what else wud cause it except some of interfernece been conducted in the throttle rod - out of two sterring servo and two brake/throttle servo - i only get glitching in the throttle side servo.i dont think its what type of radio gear u use that causes it - when i 1st started with nitro was useing entry level radio gear "futaba attack" now useing pcm receiver with futaba 3vc tranny and still get interference in a £120 throttle servo

turnell

glitching can sometimes be cause by the engines flywheel losening slighty and ending up rubbing against the ignition coil under your engine housing, give it ago it mite help.

kengentry5000

My Feedback: (2)

The Hitec has a programmable failsafe. I had the local shop program it for me. I test it before each run to ensure it is working. The Duratrax standard (included) failsafe was garbage. It caused all kinds of glitching. I wondered if the Hitec servo was pulling too much electric current through the Duratrax failsafe causing a voltage droop that the failsafe mistook for a weak receiver battery. Once I had the shop program the Hitec servo failsafe and removed the Duratrax failsafe I have not had any problems that I know of (except for the glitching described).

I assume when you mention your radio has a failsafe you mean that the receiver on the car has the actual failsafe, not the transmitter right? Probably a dumb question but I just want to get clarity here.

Ken

p113

yeh when i had nitro i always had the 50 quid set i now use the RTR controller ad does me fine im thinking of getting better radio equipment but would rather spend on performnce parts ect cus my current one works why change it until it breaks

radio_controlled_mad

cant speak for p113 as i dont know what radio hes useing but i guess its pcm gear - im useing futaba 3vc handset with a pcm 1024 receiver - you need to have a pcm receiver to enable f/s mode on the futaba handset - so one will not work without the other,good thing about that style of failsafe it will controll the 2 brake/throttle servos as well as the 2 steering servos all at the same time (3 chls in total) with out having to add or buy more failsafes.

Mad Wax

That's what I thought...Hitec Ranger II TX & RX is fine. Wrong. Crash...ah [:@][:@] lots of damage. A decent radio set might have gone to failsafe mode. I don't know what the failure was, will never know.

At least buy a Futaba 3PM (RX has a built in failsfe) only £70, and better than spending that on a new radio than trashing your model. See my recent post here (another reason for RX failsafe)

http://www.rcuniverse.com/forum/fb.asp?m=3288372

radio_controlled_mad

yeh we all start that way - you just get a bit at a time and build up,there is no way i cud afford to do buy everything in one go - every large scale owner has lied to there wives & g/f ect on how much parts realy cost - she thinks ive spent around £700 and even then she went mad - in reality prob chucked more like £2500 into my fg

p113

i know its scary how much u have spent if you were to add it up

radio_controlled_mad

yeh - but there loads of worse things you could be spending cash on - id rather spend money on r/c gear than piss it up a club wall or let it go up in smoke.

p113

yeh i hate smokers no offence if u smoke and drugs and things all pointless

SELWA

My Feedback: (1)

I've had simillar problems myself. I just picked up a SPEKTRUM radio so we will see how good the 2.4GHZ is. At least I won't have to worry about frequencies anymore!!! One nice thing about it is that it lets you use the 3rd channel for your 2nd servo for brakes or steering without the need for a "Y" harness!!!

kengentry5000

My Feedback: (2)

Yea, that Spektrum 2.4 GHz radio is very 'sexy' looking. I have some professional RF spread spectrum background with cellular phones and know the benefits of spread spectrum technology. RF noise rejection is tremendously better than FM and even PCM because you are spreading your RF energy over a much wider band of RF spectrum. Spikes of RF interference in a narrow band could wreak havoc on FM or PCM but the spread spectrum radio *should* be able to handle the glitch without any problems. Also being at 2.4 GHz at the track, you are 'miles' away in the RF spectrum from the rest of the racers. On the other hand, you are in the RF neighborhood with 2.4 GHz cordless phones, 802.11 wireless networking gear, Bluetooth gear, etc. This 2.4 GHz band is unlicensed spectrum and so any equipment operating in this band must be robust enough to survive interference from a lot of other sources. Sort of like Darwinian 'survival of the fittest' for RF equipment.

Somebody else on this forum said they were not impressed with the SPEKTRUM radio build quality. I have not seen one of these radios firsthand so I have no idea if it has poor build or design qualities.

Ken

SELWA

My Feedback: (1)

It's pretty close to the JR but for $300CAD I couldn't pass it up. There are several radios that cost more and you can get the modules but I wanted something good with that technology behind it. When I sell off my Ko-Pro EX-11 then the cost of the new radio will be even lower. At lest it's better to think of it that way!!

I was at a local BMX track where over 20 guys showed up with nitro's and 5 of us also had FG's. Lots of frequencies out there!! 1 guy had a Spektrum there and it was sweet. Most of the LHS were selling it for around the same price and when you say"cash" you may not have to pay tax!! (15%) So I saved at least $50 too!!