Battery pack and cradle as counterweight for Ioptron Mini Tower Pro mount

[Tinderboxsky (Steve)]

I have built a battery cradle to attach to the mount and act as the counter weight for my Ioptron Mini Tower Pro mount that may be of interest.

The photos probably tell the story, but to add a few other comments:

Fixing a dovetail rail to the cradle allows for it to be attached using the second dovetail clamp provided with the mount. This also means it’s position can be easily moved to assist with balancing the whole system. The grove on the back of the dovetail rail allows for the set screw adjusting lugs in the dovetail clamp to be extended forming a safety catch to prevent the heavy cradle and battery sliding off.

The battery and cradle weighs just under 4 kilos compared with 5 kilos for the supplied counter weight. However, the cradle moves the main weight of the battery further away from the mount and it turns out that its turning moment is identical to the original counter weight so I have ended up with the same counter weight result.

To balance the whole system, I first set the battery cradle at right angles to the telescope. It stays in this position permanently. I then balance with the scope horizontal using the main dovetail rail and clamp supporting the telescope. I then balance with the telescope in the vertical position by adjusting the position of the battery cradle using its dovetail rail and clamp. You can see that I have the telescope offset on its dovetail rail to do the majority of balancing on this axis. I then only have to offset the battery a small amount. I then have the system finely balanced for all positions. I have various fixed marks on each of the dovetails for quick balancing depending on what I am carrying on the scope, eg mono viewing/bino viewing etc.


With some careful cutting, the new battery cradle/counterweight fits neatly into the carry case.


As a visual observer, the advantages of this system for me have been:

• Removes the 5 kilo counter - it is stored away and does not get used.
  
• Less to carry and less to set up.
• Gets the battery and wires up off the ground.
• Provides an easy option for fine tuning the balance of the overall system
• Can all be carried within the existing Ioptron carry case.
  

Cheers

Steve.

[rcheshire (Rowland)]

Up here for thinking Steve. Great idea and nicely made.

[Marios (Marios)]

Looks good very creative use of a battery. Just wrap that bad boy in some plastic so the dew doesnt rust your terminals.

[Tinderboxsky (Steve)]

Thanks for the feed back.

Rowland, the photo hides the bruised and battered aluminium for the cradle arms that took quite a hammering to create the tight corners despite my annealing the metal to help it bend.

Mario, a good heads up! A simple plastic cover will solve this.

Steve.

[mikerr (Michael)]

Steve, great job on the battery setup

Any Idea how long the 10 Amp Hour battery will run the mount for? Should be quite some time I would imagine.

I know you can slide the cradle side to side for fine balancing, but is the shaft in the center of the battery's weight from top to bottom of the battery? Maybe that is not really critical.

How do you balance the Counterweight/Battery against the OTA? Shorten one leg of the tripod and slide the counterweight shaft in and out?

Nicely executed. I think I will have to try something similar and get rid of the fixed power lead situation.

Thanks for the thread and photos.

rgds

Michael

[Tinderboxsky (Steve)]

Thanks for the feedback Michael

I have no idea how long the battery will last! Having said that, I did experiment using 8 alkaline AA batteries in the mount holder. I found they lasted about 8 hours over cold winter nights here in Hobart - 4X 2 hour sessions with moderate slewing and they were starting to show signs of exhaustion. Also, you may have noticed on the Ioptron website that they in fact sell a purpose made battery counter weight suitable for all of their mounts. It is rated at 8 amp hours. It is also quite expensive compared with a DIY solution such as mine. So, I am confident that the 10 amp hour battery will last a long time, even allowing for only 50% discharging before recharging to ensure the long term health of the battery. I bought the correctly rated trickle charger with the battery which means it will always be ready for an observing session.

I aimed for the shaft to be reasonably close to the centre of gravity of the battery and cradle from top to bottom using a simple balancing exercise. However, as you mention, it is not critical as any discrepancy will be absorbed when balancing the system with the mount in the horizontal position.

Yes, I have tried balancing the counter weight against the scope by shortening one tripod leg. It's a bit scary! A while ago when I had all the components off the mount I weighed each item and measured their distance from the central balance point and did the calculations to work out the balance points for my different scope configurations.

One unexpected design shortcoming is that the locking knob that is tightened against the balance shaft to secure the dovetail clamp has a quite sharp point on it. So it has a very small bearing point on the shaft and has to be done up very tight to stop the whole cradle rotating on the shaft. At some stage I'll fashion a tool to hold the knob in the lathe and flatten the end to give a much greater bearing surface. Another solution would be a nylon tipped locking knob.

Cheers

Steve.

[mikerr (Michael)]

Thanks for the added information Steve.

"One unexpected design shortcoming is that the locking knob that is tightened against the balance shaft to secure the dovetail clamp has a quite sharp point on it. So it has a very small bearing point on the shaft and has to be done up very tight to stop the whole cradle rotating on the shaft. At some stage I'll fashion a tool to hold the knob in the lathe and flatten the end to give a much greater bearing surface. Another solution would be a nylon tipped locking knob."

Would filing/grinding a small flat on the shaft be an option? After all it's your shaft not mine. Maybe fit ball races in each side of the saddle so the battery holder remains Horizontal regardless of the OTA position?

Rgds

Michael

[Tinderboxsky (Steve)]

Hi Michael,

Yes, a small flat on the balance shaft would work. I had not thought of that. Having the battery pack/cradle on a bearing race won't work as it needs to be fixed in relation to the telescope in order to preserve the balance achieved in each of the the two axes.

Reading my last post when I referred to "... any discrepancy will be absorbed when balancing the system with the mount in the horizontal position" I should have referred to the telescope being in the horizontal position, not the mount.

Cheers

Steve.

[byronpaul (Paul)]

What a damn good idea ...... Thanks for posting

[astronobob (Bob)]

A great concept indeed Steve, Well done and the gel batteries are perfect for this type of Modification. . I like the thinking and a great Acheivement