r.a. motor problems

[tony gazer]

Recently got a eq4 mount with ra motor. The intructions for the ra motor n control say use no more than 6.5v, the battery pack that came with it is 9v, but it turns to slow to keep everything still in my scope. Every power tank for a ramotor system seems to be 12v should I run it on 12v or replace with something better?

[Alien 13]

A lot of the single axis motors are 6V going much higher can kill it.

Alan

[ronin]

Not staying still in the scope can just be that the mount is not polar aligned, so first question is did you do a polar alignment with the mount, have you a polar scope?

I would guess your latitude is around 52 degrees, bit less but saying 51.5 is too fine a setting for what the markers on the mount will be.

If you are to use the scope at home then if there is a round power connector, cente positive I suspect BUT CHECK. Then look at one of the Maplins L06BR AC/DC converters and set it to 6V.

Otherwise the mount drive may need a strip/clean and regrease to allow better movement.

A 6V motor on 12V will not live long.

The motor may be broken as well so you would need a new one.

[tony gazer]

Looks like it's a new motor to sort out the problem after a strip down n grease still running slow and even stopping part way through turning then starting again

[Cornelius Varley]

Which brand of EQ4 mount ?  The Seben EQ4, for example, isn't the same as the old Skywatcher EQ4 (now obsolete) or the Celestron CG4, which is actually an EQ3-2.

[tony gazer]

it's just 1 i got from orbinar as it was all i could afford at the time altho i'm already finding a few bit's i'm not happy with to much of a rush to get the bigger scope on a suitable mount 

[Cornelius Varley]

Is this the one http://shop.seben.com/sms/shop/index.php?p=b3JnYT1zZWJlbiZncm91cD0yJmxhbmc9MiZjdXJyPTE=&action=products&cat=2&mode=view&id=179 to fit this mount http://shop.seben.com/sms/shop/index.php?p=b3JnYT1zZWJlbiZncm91cD0yJmxhbmc9MiZjdXJyPTE=&action=products&cat=2&mode=view&id=177

[tony gazer]

thats the 1

[Cornelius Varley]

Strange that the instructions say 6.5volts and a 9volt 6 D cell battery holder is supplied. If you are running it at 6 volts but it actually needs 9 volts then it may be running too slowly.

[tony gazer]

even at 9v s

till running slow

[Lonestar70]

Hi Tony,

The motor speed would normally be reasonably slow for tracking purposes, probably only a few revs per minute... what happens if you use the x 8 buttons on the hand set?... it should go 8 x faster... if not then either the motor or the handset are damaged or possibly a wire is broken i one of the cables.

I would agree that you need 9V for this motor.

keep happy.

Sandy.

[tony gazer]

even at 9v still runs slow wich is realy bad as DIN standered is much better than british standard was expecting near perfection

[RichM63]

All 4 of my SW motors run at 6.5v.

Polar alignment has already been mentioned, unless it is 100% then objects will drift out of view eventually.

New batteries?

The other thing to check is the alignment of the motor output with the mount RA spindle. Unless they are totally parallel any offset can cause the motor + RA spindle to bind up in certain positions.

2 misaligned inter connected gears will have a slack spot for part of the rotation and then a tight spot when they reach the closest spot in the misalignment.

This will also be exacerbated by a less than perfect scope/mount balance because the small motor will be trying to 'lift' a heavy weight in certain positions and may cause it to 'give up'.

Hence when you watch decent videos of folk showing motorized mount techniques they will generally have no scope or weights on the mount to give the motor half a chance.

It took me almost a day of tweaking to get my modded drive system spot on for the EQ5, as small misalignment between motor and RA shaft causes the motor to work too hard, and like me, it wanted to stop for a brew.

Check the above before buying a new motor

[Lonestar70]

even at 9v still runs slow wich is realy bad as DIN standered is much better than british standard was expecting near perfection

Hi Tony,

Exactly how are you determining the motor speed?

Looking at the motor unit and the mount in the links given above it would appear that the motor unit attaches directly to the RA slow motion shaft.

If this is the case then the output from the motor unit will be extremely slow since it will be driving a wormshaft.

The wormshaft is connected to a wormwheel (inside the mount) and the gear ratio between worm and wormwheel will determine the speed required from the motor.

I don't know the exact ratio for your mount but lets take an example.

To track at true siderial rate the RA spindle needs to rotate 1 complete revolution in 23hrs 56min and 4 sec. (for this example lets just say 1 revolution in 24hrs.)

If the mounts wormwheel has 60 teeth and the slow motion worm is a single start (most likely) then the slow motion worm shaft needs to turn 60 revolutions in 24hrs (1440 minutes)... that amounts to 0.04166 revolutions per minute... hence this would be the output speed from you motor unit... it would be extremely difficult to see this small movement from the motor, let alone make a judgement as to it's accuracy.

The apparent stopping and starting is more than likely a poor alignment/meshing of the RA slow motion wormshaft with the mounts RA wormwheel... further more, if the wormwheel is of the typical accuracy found on most budget mounts it will have a highish eccentricity relative to the RA spindle. 

This eccentricity will cause the meshing of the worm to vary as the RA shaft rotates... it will be tight at one point and very slack at another...at these positions there will be a lot of backlash between the worm and wheel... the motor will need to take up this backlash before it can continue to move the RA... I.E it would appear to stop and start... additionally, any end float in the wormshaft will add to this problem.

Before you go changing the motor unit... take a good look at the alignment and meshing of the mounts RA worm and wheel and adjust the mesh depth such that it remains , as closely as possible, the same over the complete revolution of the RA spindle... also make sure the endfloat in the wormshaft is as minimal as possible.

Finally, how are the stars etc you are viewing drifting out of view?... if this is occuring at an angle (upwards or downwards) then this would point towards Polar alignment not tracking motor speed.

Hope this helps.

Best regards.

Sandy.

[tony gazer]

sorry not on here much on a device that lets my type 

was working out motor speed by colouring 1 tooth and marking where it was letting the motor run for say 5 minutes and measuring the difference and kept getting different amounts of change in location

since taken the acual motor apart at work and found it was 1 of the wire coils in it was  burnt out but having re round it( again at work) nos stays at a costant speed so seems like problem sulved

thanks for all the help and advice will let u all no if it is really sorted out