I'm new your help required please!!

[MrZuiko]

Hi my name is Ash I'm new to this forum but in need of advice I'll explain,I'm building motorised barn door mounts,one a double arm type 4 and the other is a curved rod version.
They are built from 3/4" ply probably over kill and they will be attached to a monster of a tripod that videographers use so I'm sure it will be very stable.
I've used M6 threaded rod with 25tpi,a M6 tee nut in the bottom board where the drive rod is located,spur gears for motor and drive rod (with secured blind well nut in the center of spur gear)
Arduino controlled stepper motor first time using such equipment.
So here's my problem which sounds so simple I should be kicking myself!!......the motor turns CCW and the drive rod CW it all works etc but and it's a big BUT it appears that even though the drive rod is turning in a CW direction the spur gear attached to the rod is screwing downwards towards the bottom board,where after a few minutes running can't go any further and I have to turn it off.
I've not put any load on the tracker yet e.g camera I must have done something wrong along the line,the double arm works great if you manually turn the drive rod...was I correct to install the motor and gears on the bottom board facing up,what would happen if they were installed under the bottom board,would that make any differnce? so I'm asking for your help and guidence.

Off to work now but could post a photo or two if that helps.

Regards Ash.

[Demonperformer]

Hi, Ash, and welcome to SGL.

By no means am I a DIY-er, but my (uneducated) thoughts. Presumably, irrespective of theory, if you were to reverse the direction of the motor it would perform as you want. So, do these motors work in both directions (could you just swap direction)? Could you remount the motor so it is the other way round? Would the introduction of a single gear wheel between the motor and the rod reverse the direction?

[reezeh]

I'm definitely no expert, and care is certainly needed if this is to be considered... but might reversing polarity of your drive do what you want?

Or am I thinking of the wrong thing here?

 

Don't barn door mounts usually close down as they run?

[Davey-T]

High Ash and welcome to SGL

If you search the DIY astronomer bit there are a few barn door examples on there.

Dave

[happy-kat]

Welcome.

Photos are always nice to see of project work.

My currently manual build the drive bolt turns counter clockwise on my simple but design, I can get 4 minute exposures with a 40mm lens though prefer to stick with 3 minutes.

@DemonperformerMy own barn door works by raising the top board, but there are designs out there that work the other way.

[MrZuiko]

Hi folks thanks for the warm welcome! good news I have now got the curved rod barn door tracker working a treat! nice a smooth top board opening as it should,turns out all I had to do was secure the spur gear on the motor shaft and the spur gear on the drive rod. Next is to mount the ball and socket and attach my DSLR and lens and power it up,I would like once its all set up to use my Nikkor 300 f4 see how it copes with the weight,but untill then I'd be happy just using my 50mm f1.8 and my 85mm f1.8 to start with.

Hope to have some photo's to show you guys soon gotta learn how to use deep sky stacker to stack the images,but to start I'll just go for 5 minute single exposures to check the tracking accuracy!

All thats left to do is get the double arm type 4 working!

clear skies all.

Ash.

[happy-kat]

That's great news.

The longer the lens the more actuate the mount will need to be. Have you aligned your polar finder?

[Demonperformer]

36 minutes ago, happy-kat said:

The longer the lens the more accurate the mount will need to be.

Agreed. I would start with getting it working with the 50mm before you try the 300mm. Cygnus & Cepheus are great areas for some widefield shots at this time of year.

[MrZuiko]

Hi I've got a red dot finder to put on....yeah I know the 300mm will be a long shot!! just like to see if the mount can handle the weight but would be on hand,wouldn't want my 300mm crashing on to the concrete!

How easy are the finders to align? can you simply use the hinges to sight polaris and how much off is it from the north celestrial pole or doesn't that have any effect? I enjoying watching meteor showers and star hopping with binoculars and of course photography.

I think I have found a design flaw with the type 4 mount,I was using David Trott's design but sorta changed where the motor mount would be,thinking about it now I reckon I can get working with a curved rod just to push up the main arm as the second arm has taken care of the tangent error,I just need it to drive up straight and because of the design a straight rod won't work because the main arm on my mount isn't hinged from the top with the rod driving down.....hard to explain but I think I can make it work.....!

 

Ash.

[happy-kat]

I use a straight bolt with a captive nut on top, the boards are cut from old kitchen unit so are melamine covered and the nut slides so far tangent error hasn't been apparent.

If you motorise the mount with Arduino then could code out tangent error. I previously found code online for this.

Your red dot finder must be aligned to the hinge. Hinge closed or open the RDF must stay on the  esame distant object. Polaris is good enough for the 50mm and practice will tell if good enough with longer lenses.

[happy-kat]

There is also a link in my build thread where a member shared another way to deal with tangent error that can be 3d printed to stick on the board if using a straight rod to push the board.