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Old Jul 26, 2009, 08:05 PM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
Help!
Glitch problem!!!

Hi, am working on a 1:144 scale WWII troop transport and am having a problem with glitches. When the boat is in it's stand it will run fine but when you place your hand on the bottom of the hull just forward of the prop or place the boat in the water the prop and rudder begin the glitch badly making operation impossible. I've changed crystals, moved the antenna and reciever around. It has a 540 motor with caps in place and a duratrax ESC that I run in most of my other boats and all my cars. The one thing that is different is I have installed a gear reduction in this boat. This is the first time I have used gear reduction. Anybody have any ideas. Im thinking of first replacing all the electronics and second removing the gear reduction and going with a smaller motor inline.
Also if I change motors what would be a good size for scale speed. the model is 36" long and 5" wide. It weights around 8 pounds. Thanks.
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Old Jul 27, 2009, 12:23 AM
NeverAgainVolunteerYourse lf
nick_75au's Avatar
Australia, QLD, Regents Park
Joined Mar 2007
3,725 Posts
It sounds like metal to metal contact. This will cause glitches.
Nick
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Old Jul 27, 2009, 12:23 AM
Crazy Canuck...in Dallas
Mckinney
Joined May 2009
88 Posts
is your gear reduction all metal? meaning metal gear on metal gear on metal bushing, in metal frame? you can get interference from metal to metal contact.

i'm no genius, but that seems like something to look into.
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Old Jul 27, 2009, 02:57 AM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
yes, the gear reduction is all metal. i have considered that the metal on metal might be producing an electric field that might be causing the interferance. ripping that out will not be fun but if i do i'm going to go to a smaller/slower motor in a direct drive setup.
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Old Jul 27, 2009, 06:11 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
2,995 Posts
Quote:
Also if I change motors what would be a good size for scale speed. the model is 36" long and 5" wide. It weights around 8 pounds.
Any 385 run on about half its rated max voltage. If you insist on a big motor, 545 run on a lower voltage than it rating (say 6 volts for a 15 volt motor). This will give scale performance plus a bit for good luck.
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Old Jul 27, 2009, 06:18 AM
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Joined Apr 2008
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If you still need to run that motor with a gear reduction you might think of a belt drive, the belts are rubber and usually you can get the sprockets in plastic as well. I get mine from "Stock Drive Products". If I need a gear reduction unit in one of my boats I always use one of the aircraft gear boxes, they usually don't have the problem of causing glitches.

Andre
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Old Jul 27, 2009, 09:00 AM
Big Boats Rule!
boater_dave's Avatar
Wisconsin
Joined Jun 2007
2,042 Posts
Before you rip out your current assembly, try a grounding wire to remove the interference. Get a wire and connect the shaft tube, gearbox frame and the motor.
As a test, try removing the motor pinion gear. Does the glitch still occur? Then move down the line one more step. Put the gear back on and remove the coupling between the gearbox and shaft and try it again.
Lots of boats use metal gearboxes without problems, so I bet there is a simple solution.

Dave
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Old Jul 27, 2009, 11:38 AM
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microgyros's Avatar
Glasgow
Joined Dec 2008
140 Posts
How many motor caps did you say?
The pair from the terminals to the motor case don't do anything unless you follow the advice given by boater_dave.

You have a high frequency grounding problem as your mere presence is changing the circuit.

I can't say that will completely solve it but the next steps are appropriate shield beads on the motor cables and a connection from the receiver - to the ground terminal.
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Old Jul 27, 2009, 12:48 PM
太刀風
Tachikaze's Avatar
United States, OR, Eugene
Joined Jan 2003
1,092 Posts
I would have to agree with the idea that you are having a metal to metal contact from what you are describing with the interference with picking up the boat. Prior to tearing anything out I would check a few things first.
1) with the ship in the stand, powered on with the transmitter powered on, retract the transmitters antenna and start to back away from the boat. How far can you back up before you start to get clitching? If you power up the motor, does the clitching get worse? Now repeat the same steps with the antenna up, you should be able to get up to your operating distance from the boat.
2) Now, with the boat resting on an object that would place pressure where hand would be holding the boat ( thus pressing on to the drive shaft) repeat the above steps.
If when you do step #1 and you can move 100 feet or more from the boat and little or no interference, then you can be assured that your antenna set up is fine. If on the other hand you get interference, then you probably have a transmitter or reciever/antenna issue.
If when doing step #2 you note that you have a marked interference problem then it would strongly suggest to me that you have an interference created by the interaction of your drive shaft and the stuffing tube.
I like the idea of grounding your drive line.
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Old Jul 27, 2009, 03:15 PM
Cheif Bottlewasher
more coffee's Avatar
Canada, NS, Sydney Mines
Joined Sep 2005
3,187 Posts
Actually its not grounding ..Its called "bonding"..

grounding is when you disipate potential out of a circut ...bonding allows for the objects to be at the same potential through out ..untill it leaks out ,,or goes to ground..

Any static electricity should bleed of through the dive line ,or rudder ...but if the rest of the driveline isnt bonded to them then it( the voltage or static) will be retained or remain ,,, similar to a capacitor,,

this is how a lineman in a fiber-glass man basket can reach out and hold 10-20-100 Kv without getting fried ...because he's bonded ..not grounded..... its a procedure to get there ...trust me ..
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Old Jul 27, 2009, 05:53 PM
3 Blades to the Wind
Shaun Hendricks's Avatar
Atascadero, California, United States
Joined Oct 2004
4,085 Posts
Well, you can always try running chokes as well. The trick with chokes is that they can also take out your desireable high frequency pulses.

Get a ferrite ring core from an electronics shop and wrap your servo or ESC leads through it. Start with just 2 wraps and go up. If the chattering stops, then you have finally found the turns needed to kill the chatter. However, see if the servo or motor can then run in normal proportion while on the stand. If not, you're choking down their signal also.

There are some over the counter glitch fixers available from just about any hobby store. These products range from coils to intelligent circuits that strip out 'noise' from actual circuit pulses. If you don't want to play with the cores, you can just buy some of these and be done with it.
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Old Jul 27, 2009, 06:01 PM
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microgyros's Avatar
Glasgow
Joined Dec 2008
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Seadog,if you feel like it,connect the motor case and receiver negative with a 220nF or 470nF ceramic capacitor.
Bonding?
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Old Jul 28, 2009, 01:21 AM
Tin Can Sailor
seadog985's Avatar
Alabama, USA
Joined Feb 2009
761 Posts
thanks guys, i'll try some of the suggestions. when the boat is in its stand and running i can move all around and back off a long way with no problems. its just when i touch the bottom of the hull below the shaft (no pressure applied) or place the boat in the water. then it goes nuts . the rally bad thing is with the 540 motor going nuts it really can take off.
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Old Jul 28, 2009, 05:12 AM
Registered User
Blackpool, Lancs
Joined Feb 2006
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Remarkably similar thread here
http://www.rcgroups.com/forums/showthread.php?t=1085126
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Old Jul 28, 2009, 05:46 AM
Registered User
microgyros's Avatar
Glasgow
Joined Dec 2008
140 Posts
Quote:
Originally Posted by mfr02
Possibly a duff motor to case capacitor or direct short.

Which is why it is safer to RF ground via a 220nF-470nf cap.
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