A Telecope Dolly

 

Soon after I had purchased my Meade 12" LX200 telescope, I realized that I would not tolerate a routine of carrying the telescope tripod and OTA out of daytime storage in the garage, assembling them in the driveway, then breaking the telescope down late at night and carrying the tripod and OTA back in the garage. Main reason: the tripod weighs 50 pounds, the optical tube assembly 80 pounds.

So I started looking around for simple transport alternatives. At first I browsed online for products: JMI offers a range of "Wheelie Bar" dollies for around $300, and Scope Buggy a line of less elegant but equally serviceable products for slightly less money. (Both are linked below.)

I also found several homemade designs that were basically attachments or customizations to a standard hand cart or hand truck, but these seemed unsuitable for a large instrument, and would require the tripod to be partially or complete closed — a serious hazard as well as an inconvenience with my weighty telescope.

As the commercial prices were probably about what I would pay for a custom made unit, I began drafting plans for a steel tripod dolly that could be fabricated by a local welding shop. However, once the plan had materialized I concluded that it could just as easily be made of wood — something I could do myself. So I dug out my mitering saw, power drill and tape measure and built the platform dolly pictured above.

The parts list includes:

• 3 pieces of 2x4 fir, about 40" long (the length varies, depending on the dimensions of the tripod "footprint")
• 2 pieces of maple high pressure plywood, 1/2 thick and roughly 24" square
• 6 3" carriage bolts and hex nuts
• 12 steel washers
• 3 dolly wheels, at least 2" diameter, with locking mechanism
• 6 strips of rectangular hardwood or moulding, about 12" long
• 12 1" steel wood screws (to fasten dolly wheels)
• 12 1" finishing nails (to fasten lath strips)
• 6' of inelastic cord (steel core laundry line or heavy duty nylon cord works best)
• Gorilla Glue

Tools required: a hand saw (better is a power mitre saw or table saw), power drill, tape measure, inelastic cord (steel core laundry line or monofilament nylon works best), chalk or carpenter's pencil; a wood drill to match outside diameter of carriage bolts.

Total materials cost: $70.

The assembly proceeds as follows:

1. Measure the height of the dolly wheels, from the bottom of a wheel to the top of the attachment plate.

2. Configure the tripod so that the OTA is at your comfortable viewing height for an OTA elevation of 30° above the horizon; then configure the tripod so that it is lower than this height by the height of the dolly wheels, plus about 1".

3. Find the average distance between two tripod legs. (Measure the 3 distances between each pair of tripod points, add together, and divide by 3.) Multiply this distance by 0.6 (or 0.5774): this is the distance from a tripod point to the center of the triangle defined by the three tripod points. Add 6" to this length: this is the finished length of each of the 3 horizontal dolly arms.

4. Use a box or power mitre saw to cut one end of the 3 2x4 fir arms to a 120° centered point. Measuring from this point, saw the other end to the finished length.

5. Saw the two plywood squares into equilateral triangles with 24" sides; trim the points from the triangles. (To define an equilateral triangle, use the inelastic cord with one end securely looped around the point of the carpenter's pencil. Place the pencil point at one corner of the 24" plywood square, and with the cord firmly anchored with your thumb at the opposite corner, draw an arc across the board. Do the same from the opposite corner. Where the two arcs meet is the third corner of the triangle.)

6. Lay the three fir arms on a perfectly flat, level pavement or work surface, positioned so that the points are perfectly joined and the arms are exactly 120° apart. To guide this step, use an adjustable mitering angle if you have one and trust it. I chose a simple workaround: I used some inelastic cord or fishing line and a carpenter's pencil as before, this time to draw a very large circle on the pavement and then to divide the circumference into six equal segments using arcs drawn with the cord radius. Lines from three alternating marks to the circle center define the 120° angles.)

7. Center and align the two plywood triangles on top of the fir arms. Number the top surface of the arms "1", "2" and "3" in clockwise order, and copy these numbers onto the corresponding corners of both triangles.

8. Drill two bolt holes for each arm, on center and spaced about 6" apart, through both pieces of plywood and the fir arms. Use a drill that is exactly the bolt width, so that there is minimum freedom of movement in the fir arms.
—> There are alternative, more professional methods to measure, align and drill the holes. If you are skilled enough to use them, you know them already.

9. Test assembly fit of the pieces by inserting all six carriage bolts through the holes, with the plywood pieces on opposite sides of the legs. Make sure to match the numbering of corners and legs.

10. Insert the six carriage bolts with their head washers into one of the plywood triangles, and lay it down with the bolt ends pointing up. With each arm in turn, moisten facing areas of the fir arm and the plywood, and the joint between arms, apply Gorilla Glue or other wood glue, and press the fir arm onto its pair of bolts, again making sure to match the numbering and orientation of arms to triangle plate. (Also, have a hammer ready in case the fit is tight.) Moisten the second piece of plywood and facing fir arms, apply glue, and insert over the bolts. Add the nut washers and hex nuts, and use a wrench to tighten the bolts firmly. Allow glue to cure overnight.

11. Use wood screws to attach the 3 cart wheels to the three fir arms, about 6" from the outer ends (that is, directly under the measured location of the tripod points).

12. Attach two 12" lengths of hardwood or moulding to each arm, spaced to accommodate the width of the tip of each tripod leg. (You may also want to score or cut the center strip with a drill bit, to give the tripod points some traction.) These strips hold the tripod firmly in place, but allow for changes in the tripod height. Moisten facing surfaces, apply Gorilla Glue, and secure with finishing nails at each end.

The total assembly time, not counting the purchase of materials and parts, was under 3 hours.

The commercial dollies have threaded rod footpads that can be used to raise the telescope onto three fixed supports. These are difficult to construct with sufficient strength in lumber fittings. I found it is quite easy to lift one of the legs at a time, for example to place a leveling piece of plywood underneath one of the cart wheels; three blocks of wood can be inserted in the same way to lift the wheels entirely off the ground.

However, I have found that the wheel locking mechanism is quite adequate to the task: orient each wheel so that it is turned outward (as shown in the photo, above), and then lock the wheel. When all three are locked in this way no wheel can move without pushing against the other two, and this is sufficient to keep the whole tripod stable for all routine tasks, including mounting and unmounting heavy eyepieces, dew shields, etc.

It was a clear night the day I completed the dolly, and without the moon there was a lot to observe. Fortunately the telescope's goto computer found objects efficiently, and i saw quite a lot before the dew set in and everything fogged over. So I rolled the telescope back in the garage, and went to bed for another chapter of Tristram Shandy.

Further Reading

Wheelie Bars, commercial tripod dollies at Jim's Mobile.

The Scope Buggy, another commercial tripod dolly.

The Tripod Sled by Ed Stewart. Instructions for a home made tripod platform, transported with a standard mover's dolly.

Scope Transporter by Dave Dixon. Another transport system based on dolly customization.

LX200 Field Transport System by Alan Jones. And yet another dolly device, by now you get the general idea ...

 

Last revised 11/26/13 • ©2013 Bruce MacEvoy