motors

[Gordon BlanksParticipant @gordonblanks18647]

hello all i have just put a new motor in my boat .problem  prop turns on forward ok but when i put it astearn  it  shudders  it is not smooth running very jerky  any help gordon

[Paul TParticipant @pault84577]

Try these

1/ Prop or shaft not balanced or shaft bent

2/ New motor not correctly lined up with the shaft

3/ Motor – shaft coupling out of alignment

4/ New motor not secure in its mounts

5/ Is the rudder loose or have any sidewards play in its shaft

And questions would be:

Does the shuddering occur across the full speed range or just at certain revs?

Is the new motor the same type and size as the old one?

Did the boat suffered any underwater damage or strike anything during the new motor test?

Paul

[Gordon BlanksParticipant @gordonblanks18647]

nodamage to boat  shuddering only on reverse correct speed on forward .only on reverse dose not seem to want to go. in reverse seems to stick gordon ps motor is smaller than old one

[Gordon BlanksParticipant @gordonblanks18647]

was running motor on 6volt  connected 12volt no problem  12v to heavy for  revell snowberry  gordon

[60wattParticipant @60watt]

sounds like it could be sorted by .switch contact cleaner or tightening a nut tommy

[Len OchiltreeParticipant @lenochiltree67043]

Is the prop shaft moving slightly backwards and the prop catching against the rudder ?when in reverse.

Len

[Gordon BlanksParticipant @gordonblanks18647]

thanks 60 watt  and len plenty of room between prop will try a bit of wd on electrics as i mentioned ok on 12 v thanks gordon

[60wattParticipant @60watt]

Hi Gordon. 

I assumed you were using a bobs bored because you mentioned these before.They did cause a stutter if they were not attached to the servo properly.

The 12-ok then 6-not-ok is a common problem when you try to use bec with a speed control on a 6 volt supply which is not enough.

Some older 6-12 speed controllers used a  6 volt reversing relay whose coil was powered by the drive battery via a resistor. The extra resistance meant the pulling force too weak.

More info would speed the process along

Tom

[Gordon BlanksParticipant @gordonblanks18647]

hello tom yes i am using 6v with bec  the speed control isa seahunter 25 amp high frequency micro control as i said ok on 12v thanks gordon

[60wattParticipant @60watt]

Ah….sea hunter!

It is indeed a low voltage problem.

The unfortunate side-effect of the overcurrent protected transistors in some escs is that they have a minimum threshold voltage.

Tom

[Gordon BlanksParticipant @gordonblanks18647]

hi all . what is the best remerdy

[60wattParticipant @60watt]

The speed control drive stage does not work at a low voltage so you would have to go with a 7.2 minimum  battery.A motor with a lower stall current would not trigger the voltage dropout but a 6 volt lead acid battery would not have enough headroom to supply the receiver anyway (through  the speed control battery eliminator circuit).

I wonder what motor and prop you use because the scale prop for that corvette is rather large for direct drive for 385 and even 380 motors.Perhaps a 555 motor from RS components and a small 12 volt or  7.2 or 8.4NiMH battery would be in order anyway.

You could kill two birds with one stone.

Tom
  

[Gordon BlanksParticipant @gordonblanks18647]

hi  tom the boat is fitted with a 30mm?///or on my tape1 1/4 inch the motor is a 385  direct drive have just found a 3000 7.2 ni batt will charge it and see if any better  if not will have to remember no reverse  thanks gordon

[Gordon BlanksParticipant @gordonblanks18647]

hi tom fitted a 7.2 3000 batt to boat  reverse ok  but wiil go with 6volt  for ballast and very slow reverse thanks to all gordon

[60wattParticipant @60watt]

Hi Gordon.

I confused your esc with another Ripmax type.It still might share that problem on six volts but you have the instructions not me.

I suspect it has a "car" profile in that reverse power is limited to 50%.

I wish you good luck as you are going to have no end of problems on 6 volts without a dedicated battery for the rudder and receiver as most people find out.

On top of that the 385 will be scorching hot after a while unless you use the smallest,shallowest pitch propeller you can get your hands on. 

Tom

[ashley needhamParticipant @ashleyneedham69188]

All..  I have 385`s on my HMS Devastation battleship with 40mm brass props on 6v and they run all day at just being warm, same for me Titanic at 35mm props. Dont see a problem,  385`s are nice torqy little motors, and quite pokey when run at 12v.   Ashley

[60wattParticipant @60watt]

Hi Ashley.

I noticed you made that observation before. I too have used them and found the optimum propeller size a lot smaller.

 My own tests tally with MFA data and the 385 is on the bottom of the league table if you ignore the little tiddly motors.

Tom

[ashley needhamParticipant @ashleyneedham69188]

Tom. It may be that for  optimum efficiency the prop should be smaller than I use, but it seems to me that they WILL spin a larger prop. The current draw is very modest to start with so perhaps even overloaded a bit they still only draw a small ampage.  I have never bothered to put a meter on one, The pair on the battleship last for  well over  1 1/2 hrs on a 6v 4.5Ahr battery which is usually enough for me !   Ashley

[60wattParticipant @60watt]

Hi Ashley.

I can see you favour a less quantitative approach.

Some time I’ll get round to filling in the blanks in the performance data of the common model boat motors. It would be in the vain hope thet fewer people will be suckered into wasting money.The science is simple enough.

Tom

[Gordon BlanksParticipant @gordonblanks18647]

 getting to much for me i will go back to elastic bands  gordon

[60wattParticipant @60watt]

There might be a clockwork mechanism going cheap somewhere.

[Gordon BlanksParticipant @gordonblanks18647]

hi or a very large hammer gordon

[Gordon BlanksParticipant @gordonblanks18647]

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