Motor 'stutter' - Page 2

scottie2212 · 26-07-2006

The end may be in sight....

Following extensive testing in my bath this morning, I have isolated the cause of this problem!!!
This 'stuttering' only occurs when full power is applied forwards, reverse does not suffer at all. Also, both motors stutter at exactly the same time. 'Ah, receiver problem,' I hear you cry. But no, it happens with a genuine Futaba receiver as well as the 'cheap' one.

The problem lies in the speed controllers... believe it or not!!!
I have borrowed an older Sonic 15 from another boat and tried it alongside one of the Vipers. The Viper stutters, the Sonic runs perfectly.

I have just finished speaking to Mtronics who are as mystified as I am but, being the helpful people that they are, have asked me to send the Vipers back with a note about the problem. Now I can only hope that they will be able to duplicate the fault.
Added to that, I have a Viper 25 which exhibits similar problems. Unfotunately I can't put the boat in the bath and don't have a spare 25 amp controller to test it against.

Andrew, are you using the same ESCs i.e. Mtronic Viper? If so this may be the same problem.

I'll post any reply I get from Mtronics in this thread.

Scottie

**wonwinglo** · 26-07-2006

Just had a thought on this Scottie seeing as it is ESC related,you have not extended the speed controller cable by any chance ? I had one make that refused to function altogether if the cable was extended,it took me weeks to find out the cause ? can be fiddly things sometimes.

scottie2212 · 26-07-2006

Hi Barry,

I assmue you're talking about the ESC cable that goes to the receiver, no I haven't extended that one at all. All I've done is removed the positive wire to disable the BEC function, as per instructions.

Scottie

**Bunkerbarge** · 26-07-2006

Well done Scottie. You wouldmn't have thought thatv two ESC's would have exhibited the same problem at the same time.

Still perseverance is the only way. As I often say with these things, the fault is on the desk in front of you, all you have to do is find it!!

scottie2212 · 26-07-2006

These ESCs have a built-in overload cut-out. When I spoke to Mtronics he asked what current my motor was drawing. Since I'm only drawing 2.2 amps max (full throttle and under load) I can't be getting anywhere near the stated max of 15 amp. My thought is that perhaps a 'batch' of controllers have got faulty components within the overload circuit. Since I bought them at the same time it would explain why they are both doing the same thing.

Scottie

davemboater · 05-08-2006

Hi. Having read your post I offer the following comments
You mention 1 uF capacitors for suppression, I only use 0.1 uF caps. I believe the high value is giving a smoothing effect to the speed controller output, resulting in the effect you are experiencing. Also if you are using standard electrolytic caps they will be polarised ( i.e. + to +) and will therefore be reversed connected when you change the motor direction. The voltage across the motor will also be greater than the supply voltage and this may be exceeding the capacitor max volt rating, causing the caps to break down. Mtronics may well suggest a value.
I agree with the other posts re metal to metal links causing interference and sugest you check and replace any metal to metal links.
From your picture it would appear that you may have some signal wires running near to high power wires(ie battery). It would be better to ensure that the aerial and any servo leads are routed well away from the power carrying wires, including any auxiliary circuits (eg lights, sound effects)
Hope this helps. I have several tugs with two motors and have not had your problems.
Dave

scottie2212 · 14-09-2006

Update on my problems with ESC's...

Sorry for the long delay in updating this. Mtronics duplicated the fault I was expereincing (thank ... (insert diety of your choice)) and sent me replacements which, would you believe it, exhibited similar problems. While one of the new ones was okay the second was acting even worse than the originals. i.e. It stuttered at less than full power setting. I again spoke to Mtronics who could offer no advice as to why it was happening but said it might help if I could visit them with my model so they could see it in-situ.

I've just returned from them with the problem all but resolved.

Following lots of testing we discovered that the problem is linked to the BEC circuit!!!! I know this seems strange but it is true. As per instructions in the packet, I removed the positive lead from one ESC before plugging both into the receiver. The ESC with no positive connection to the receiver is the one causing trouble. When we put the lead back into it's shell the problem vanished.

Mtronics tech guy (a really nice lad called Paul) was as mystified as me but at least we now know what is causing the stutter if not the reason why it is happening.

The current status is that my model is working properly and Paul is going to investigate why the BEC circuit is causing the problem. He has said he will pass on relevant info to me as soon as he has any.

Scottie

**Bunkerbarge** · 14-09-2006

...and all credit to Mtronics for following this up so positively and not fobbing you off with the usual crap we get all too often nowadays.

Thanks for sharing this with us.

ajg141 · 14-09-2006

Excellent news Scottie and many thanks for the update. Mtronics seem to have been very helpful. I was about to order a couple of new escs for forthcoming projects so I know where they're coming from now!

Andrew

scottie2212 · 14-09-2006

In my opinion, Mtronics have proved themselves to be a company well worth dealing with.

They have already replaced to blown-up ESCs without question, in this day and age that's remarkable by itself. Add to that their willingness to help with a 'strange' problem puts them right at the top of my favourite list of model equipment suppliers
Until I start building my own ESCs (something I am seriously thinking about doing) I will ALWAYS buy theirs.

Scottie