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Author Topic: RC Servo with Ball Bearing Construction  (Read 2281 times)

derekwarner

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RC Servo with Ball Bearing Construction
« on: May 27, 2016, 02:52:38 AM »

Guys........... I have hidden a standard JR NES-537 in a wooden box.....also cut off the endcap mounting lugs & installed M3 side mounting tapping's

The issue is 3mm deflection of the servo extended arm of approx. 75mm high...the servo is of plastic bushed construction.....no fault of the servo, just my intended use

I am hoping that an alternate servo with metal gears & double ball bearing construction will greatly minimise the deflection

HobbyKing list a number of servos with metal gears & BB construction, however has anyone experienced the use of such an item?

Derek
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Derek Warner

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malcolmfrary

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Re: RC Servo with Ball Bearing Construction
« Reply #1 on: May 27, 2016, 09:32:36 AM »

With the relative distances involved, I'm not sure that a BB servo would be much better.  Better, yes, but better enough?  A smaller servo geared to a shaft with more widely spaced bearings should lose any unwanted wobble.
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JimG

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Re: RC Servo with Ball Bearing Construction
« Reply #2 on: May 27, 2016, 11:28:15 AM »

A very intriguing piece of equipment, whatever its used for. It really needs a bearing at the top of the shaft holding it in place to stop any deflection. A BB servo will help with keeping the bottom centred however metal gears will not give any improvement. Normally metal gears are called for where there is a lot of vibration as with a petrol engined model.

Jim
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Bob K

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Re: RC Servo with Ball Bearing Construction
« Reply #3 on: May 27, 2016, 11:49:55 AM »

That is a very long assembly, driven from just one end.  You need the other end supported or the pull on the various ball joints will twist it badly.  I had occasion to require a longish drive pillar (not as long as yours) operating a toothed belt driving two sets of gear driven rudders.  I put a 5mm thick Perspex plate as a support near the top end, the plate being held by four screws.  Even a Perspex guide at the top will prevent twisting and failure.  So far it has worked well with minimal wear on the top support, which is easy to replace if needed.
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derekwarner

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Re: RC Servo with Ball Bearing Construction
« Reply #4 on: May 29, 2016, 12:00:28 AM »

Thanks for the responses

Opened up a JR NES-537 & the output bearing element is ~~ 2.5mm high bronze filled Teflon band & the pinion shaft is free to wobble  O0...........

So have ordered an HK analogue, metal geared, dual ball bearing servo for $21.00 delivered......will test it, the cut the legs off & disguise is as another wooden box  {-)

Derek
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malcolmfrary

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Re: RC Servo with Ball Bearing Construction
« Reply #5 on: May 29, 2016, 08:34:30 AM »

I still think that to eliminate the wobble with that length of shaft, the bearings will need to be a lot further apart or some other means of steadying it - maybe a supported disc inside the box.
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derekwarner

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Re: RC Servo with Ball Bearing Construction
« Reply #6 on: May 29, 2016, 09:54:26 AM »

Yes ...I agree Malcolm......, however aesthetically I must try the anticipated extra rigidity of the BB output shaft servo first..... Derek
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derekwarner

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Re: RC Servo with Ball Bearing Construction
« Reply #7 on: June 02, 2016, 05:23:05 AM »

OK...this standard NES-573 in the wooden box goes back for reuse in another location & will await the BB mounted servo unit & then disguise it  :o in another wooden box  ;D ............

I will come back with a comparison deflection between the standard output shaft & the BB housed shaft......... Derek
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tigertiger

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Re: RC Servo with Ball Bearing Construction
« Reply #8 on: June 02, 2016, 07:45:46 AM »

From my limited experience.
High torque will be more robust. For you application, cheap servos are more likely (not certainly) to have more play in them.
But high torque, quality are much more expensive.


I did have another thought. If you can extend below the box (maybe you don't have space) you might benefit from being able to use a stiffer shaft and bearings at the top and bottom of the box.


Just thinking outside of the box, pun intended. %)
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derekwarner

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Re: RC Servo with Ball Bearing Construction
« Reply #9 on: June 02, 2016, 08:11:30 AM »

Thankyou TT  %)........your alternate arrangement sure would help, however  <*< won't fit.................. Derek
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RAAArtyGunner

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Re: RC Servo with Ball Bearing Construction
« Reply #10 on: June 02, 2016, 12:44:16 PM »

Derek,

Following on with TT's idea, can you make the "shaft" the same thickness throughout it's entire length, rather than reducing it, which induces 'whiplash'.???????
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inertia

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Re: RC Servo with Ball Bearing Construction
« Reply #11 on: June 02, 2016, 02:03:30 PM »

How about bevel gears with bearings in the sides of the box?

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derekwarner

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Re: RC Servo with Ball Bearing Construction
« Reply #12 on: June 09, 2016, 11:11:18 AM »

Well...with the new HK 15288A servo with double BB, the deflection appears to be near halved to approx. 1.5 mm at the same 75 mm effort arm height

Considering this motion will be of extremely low frequency [engine reversal], and with lowered speed via the ACTion P96 servo morph.....I think will be OK................ %)

Just now need to encase the servo in another wooden box {-).....

Derek
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Derek Warner

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