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Old 03-05-2003, 07:40 PM   #1
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Arrow Car just started jerking out of nowhere...

Went to the track today and ran a good 2 runs. On the third run, I didn't change anything with my setup. I put the battery in and plugged it in. Set the car down on the track and got to go around 1 full lap before the car started jerking. I asked everyone if they had the same frequency as me...and no one did. I took the car to the pits to see if a connection maybe got messed up. Nothing looks unusual. I put the car back out there and it kept doing it. I took the motor to the guy at the desk and I asked him to test the motor to see if maybe something was wrong with the motor. It tested fine. So, now I must find where the jerking is coming from. Obviousaly there is something interfeering with the signal coming from my radio. How could I test to see what it is. It could be the ESC or the receiver. I don't wanna replace stuff that doesn't need to be replaced.

Anyone have a clue on something I could check. I had everything set up perfectly for the race on Friday...and now this. The race starts at 7 PM on Friday so I am going to get to the track at around 3. Hopefully I can get the problem worked out before qualifying...if not...home I go.
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Old 03-05-2003, 07:47 PM   #2
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try a different set of crystals. If you had a big hit on your previous pack you might have damaged them slightly. If your problem is still there with a different set take a look at your transmitter batteries. If that's not the case then look into the receiver. Hope this helps some.
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Old 03-05-2003, 07:54 PM   #3
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info above is good, also it could be a blown FET in your speedo, aftr changing crystals try borrowing another reciever and then another speedo. I had a club mate who didn't realise his problem for ages, he could drive the car but whenever he got near full power or hit the throttle hard the car would become jerky, he knew he had a problem with reverse not working and in the end it turned out the blown reverse FET was causing all his problems. this is after trying differnet radio sets, rewiring his car several times, trying different positions for his electronics and more.
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Old 03-05-2003, 08:52 PM   #4
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Default Car just started jerking out of nowhere...

unknown;

When is the last time you had the Com cut on your Motor and changed the Brushes? Just a thought.
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Old 03-05-2003, 08:58 PM   #5
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The problem happened right after I cut the comm. So, that isn't that problem. Plus, I had a guy test the motor to see if that might have been the problem...and the motor was fine. I will try different crystals first, then move to a different receiver, then try a new speedo. I have been looking around for a new speedo...and now might be the right time to get one. Thanks for your help.

If anyone has any other thoughts...lets hear em.
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Old 03-05-2003, 09:08 PM   #6
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Quote:
Originally posted by unknown
The problem happened right after I cut the comm.
If the Car was fine before, look at something going on when the motor was worked on. Unless you had a BIG crash that could have damaged something. Maybe the Caps on your Motor are Bad or Fell out (SMC's).
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Old 03-05-2003, 09:15 PM   #7
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Quote:
Originally posted by unknown
The problem happened right after I cut the comm. So, that isn't that problem. Plus, I had a guy test the motor to see if that might have been the problem...and the motor was fine. I will try different crystals first, then move to a different receiver, then try a new speedo. I have been looking around for a new speedo...and now might be the right time to get one. Thanks for your help.

If anyone has any other thoughts...lets hear em.
when you cut the com did you clean out the groves with an exacto blade and run a ball point pen to roll down the sharp edges. could be a shaving causing a sort between the poles

just my 2cents
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Old 03-05-2003, 09:55 PM   #8
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no, i did not run an exacto down the groves or run a pen either. I knew I forgot something. I just got my comm lathe today and had one of the workers there show me how to use it. What he didn't tell me to do was run the exacto and the pen on the groves. I watched someone tru a comm before and I remember him doing that. That is prolly my problem. But the thing that gets me is that I has the motor tested on a motor run in and it worked just fine. It was drawing a steady current.
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Old 03-05-2003, 10:03 PM   #9
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By the way...I got the X-MOD Perfect Lathe for $118

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Old 03-05-2003, 10:09 PM   #10
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Quote:
Originally posted by unknown
no, i did not run an exacto down the groves or run a pen either. I knew I forgot something. I just got my comm lathe today and had one of the workers there show me how to use it. What he didn't tell me to do was run the exacto and the pen on the groves. I watched someone tru a comm before and I remember him doing that. That is prolly my problem. But the thing that gets me is that I has the motor tested on a motor run in and it worked just fine. It was drawing a steady current.
just because the motor tested out fine. dosen't mean it does not cuase radio interferance. It may sound funny but the brushes may be jumping due to the sharp ridge left on the poles alos did you change the brushes ( please say yes) and did you use good ones or the hobbie shop bulk stuff???

nice lathe.... mine is an old cobra mod lathe about 11 years old

cool avitar.. is that a dude from ICP. My kid loves that stuff
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Last edited by howard hudson; 03-05-2003 at 10:12 PM.
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Old 03-05-2003, 10:22 PM   #11
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have to agree that you should check your brushes. are they new? if they aren't, are they significantly worn out/short compared to a new brush? also, check your spring tension. since you said the problem started after you cut your comm, that means your comm diameter has become smaller. if this is a motor that has been cut quite a bit and has a com running below 7.0mm in diameter, maybe you'll need slightly heavier springs to ensure that the brushes aren't cogging, skipping, or things of the sort. just a thought ....
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Old 03-06-2003, 03:22 AM   #12
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transmitter batteries low?
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Old 03-06-2003, 07:23 AM   #13
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The transmitter batteries are new.

As for the brushes, no I didn't change the brushes because there were only ran one time. They are Trinity 99-Plus brushes...not some bulk ones.

I haven't checked the spring tension on the brushes...I will do that on Friday.

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Old 03-06-2003, 08:33 AM   #14
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Default Car just started jerking out of nowhere...

unknown;

Use the Exacto knife blade to clean the Grooves between the Com segments. Then use a Ball Point Pen on the Grooves to roll the any Burrs left, down nice and smooth.

I have the EXACT same Lathe and it has worked great for me.

Tip on the Lathe:

Put a Drop of Bushing Oil on the sides of the Roller Bearings for lubrication, every few uses. This will keep them from wearing out and getting sloppy, causing a rough cut.
All you need to use for Cutting Lube is a Sharpie Marking Pen. This is plenty of lubrication for the bit and doesn't make a mess. (got this from some Pro Drivers)

Make sure that you Break-in your Motor for about 3-5 minutes after Truing the Com or changing the Brushes. This is very important to keep the Brushes from Arcing too much. A 2 or 3 cell pack works good for this.

Last edited by popsracer; 03-06-2003 at 08:40 AM.
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Old 03-06-2003, 11:01 AM   #15
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Also a servo going bad can cause your car to glitch. Try unplugging your servo from the receiver and turn the car on and see if it glitches. If it does then try another receiver and see if it glitches or not. If it does then it is more then likely your speedo.
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