Sunday, January 5, 2020

Wheels

The Wheels on the Bus go round and round . . .

It's not a bus, but it needs wheels anyway.

My new Celestron CPC 1100 is big and heavy.  With its optical tube assembly (OTA) weight approaching 75 lbs (includes focal reducer, focus motor, and 2" diagonal) and its tripod another 36 lbs,  it's not as big and heavy as some of the other choices that I had considered, but it is marginal in terms of me being able to set up and take down without assistance.

I can carry the OTA assembly from the house, through the garage, and across the driveway to my preferred observation spot and get it mounted on the tripod without too much difficulty as long as I don't have to lower the OTA to the ground and lift it again.  That is the troublesome part of the procedure as it is necessary to remove the OTA from the tripod and carry the tripod out first.

But, what if I could just keep the tripod and OTA together and just move the complete assembly?

It turns out that there are a number of "Scope Buggies" choices that one can purchase to perform that task.  Oh, my.  They are expensive.

I decided to try a DIY approach.

It took a while, but a plan coalesced.  

Thoughts captured in my notebook.  Artsy, huh!?
I made a trip to Lowes, our nearby home improvement center, for supplies and got started.

A 2 by 4 seems a good choice.  The wheel is a 4" caster with a rubber tire.
I carefully lay everything out while measuring, pondering, and building my DIY scope buggy. 

A "Y" configuration seemed to offer the best choices for tethering the tripod to the base.  It also turns out that the doorway to the garage is too narrow for any other approach.  The tripod needs to be "rotated" on its way through.

Wood glue and carriage bolts. 

All of the actual construction occurred in the garage, for migration mitigation of sawdust and wood chips.

Tripod on wheeled base.

The tripod fits nicely on the wheeled base and is firmly attached to it.  I sat on the top of the tripod to test its robustness.  The wheels are rated for 155 lbs. That gives me some margin.

I have two concerns with this scope buggy.  

It elevates the tripod 7", necessary to overcome some obstacles while rolling to the observation spot.  (One of the obstacles is a door threshold and subsequent ramp.) This higher CG is scary.  Testing has shown that there is no danger of it tipping, though.  I did leave room on the base to add weights to lower the CG if necessary.

The tripod looks precariously perched on the platform.  It is firmly anchored via a bolt on each leg attached to a bracket and some carriage bolts.  To test its attachment, I picked up the tripod and lifted the base along with it.  Nothing wiggled.

Doesn't budge.
The eyebolt, tripod bolt hole, and bracket combination seems to be made for this purpose. Note the curve of the bracket, necessary for alignment with the eyebolt.  Where did I get this bracket?  From the plumbing supply section of Lowes!  Oh, the things I find!

Curved bracket and wood screws.
Here is the completed assembly.

Sitting pretty.
It has made a couple of test excursions through the doorway and down the ramp.  Seems stable enough.

Whee!
What next?

By placing the assembly on a rubber wheeled platform, I've introduced some springiness to the system and lost the ability to adjust levelness.

There are a number of ways that I can address this.  Here is one of them.

Simple scissor jack from my car.
I would need 3 scissor jacks, making this an expensive solution.  This particular jack has some "slop" of its own, making me question this approach.

This is what I use to level my Dob.  

Scope leveler via carriage bolt, nuts, bracket, and epoxy putty.
I'll probably do something like this on the tripod platform.  I haven't quite figured out how to mount it or even if it'll scale to the heavier weight of the system.

The big question still looming, however, is what color should I paint it?  Any ideas?



















2 comments:

  1. Yay for getting the tripod mounted on the castors. I know that was quite the project! Hmm, what color . . . well, do you HAVE to paint it?

    ReplyDelete
    Replies
    1. I don't really want to paint it, but it probably needs to be protected against the dew. I'm thinking of a clear polyurethane or maybe hot pink. 😎

      Delete

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