AstroDesigns

2-D Counterweight Design

by Rick Woods <rvwoodsa_tjuno.com>

I designed and built a rock-solid, sliding rail 2-D counterweight system, on top AND bottom of my 14" LX200GPS, and want to share it. I only spent about $20. (It may cost you a little more, as I had some of the nuts and stuff on hand.) The entire project can be completed in a single day. Here's what I did.

Overview of 2-D Counterweight
"Figure 1" shows the scope from the side, with the top and bottom rails. The weights in the back on top and bottom (on the "Z" brackets) stay there all the time. The extra 2-D sliding weight toward the front can be used as needed.

The sliding rail is a length of 7/8" Unistrut. It works perfectly. All my measurements are based on the 14" tube, so you'll have to modify them for your scope, but my parts list is:

1 - 5' length of 7/8" Unistrut
1 - 4' length of 1 12 x 1/8" steel bar stock
2 - "Z"-shaped Unistrut brackets
2 - 3/8" Unistrut nuts
6 - 1" x 3/8" hex cap screws
6 - 3/8" washers
4 - 3/8" lock washers
4 - 3/8" hex nuts

  1. Cut the Unistrut to a piece that extends from the front to the back of the scope tube. A sawzall type saw makes this a lot easier.
  2. Cut the steel bar stock into 4 X 1-foot pieces.
  3. Put a mark in the middle of each piece of steel. This is where you will drill a 3/8" hole to attach the steel to the strut.
  4. make a line widthwise 1" to each side of the center dot.
  5. Make another line about 5/8" beyond the first one.

You now have 4 lines. Now comes the hard part. Take the steel, put it in a vise, and pound it with a large flat-surfaced hammer. Bend it along the two inner lines at a 45 degree angle, so that you have a sort of a U-shape. Then bend along the two outer lines in the opposite direction. What you want to end up with is a bracket, shaped to the contour of the telescope tube, with a raised center that will allow the head of the 3/8" hex cap screw to come up through the bottom and poke through the strut, while clearing the telescope body. make two of these brackets for each of the top and bottom of the scope (4 total).

Close-up of brackets
"Figure 2" is looking at the bottom rail from the front, and shows detail of the bracket and 2-D sliding weight arrangement.

Now measure carefully, and mark where the attachment screw holes need to be on the bracket. Drill the two attachment holes so that the screws from the telescope rim will fit through them. Drill the center hole 3/8". Draw a line just beyond the holes, and cut off the extra steel. It's a waste, but the extra length made it a lot easier to bend.

Attach a bracket loosely to each end of the piece of strut. Remove the attachment screws from the ends of the scope and put aside the washers. Screw the brackets to each end of the scope, then feed onto each 3/8" cap screw a washer, lock washer, and 3/8" nut. Tighten everything down. I used regular hex nuts here so when I want to loosen one end of the strut, I can do it from the outside with a socket. Paint the whole assembly if you like.

Close-up of upper unit
"Figure 3" shows the top rail from the rear, showing the weight assembly held on by a strut nut.

Now, my scope is very nose-heavy. I attached a "Z" bracket to the very back end of the strut, behind the bracket, with a 3/8" screw and strut nut. The "Z" is attached so it rises away from and to the rear of the telescope body. the weights used are the old metal barbell weights, attached to the top rear end of the "Z" bracket with a big bolt and wing nut. Very solid.

I made a rail with "Z" bracket for the top and bottom, and put 5 lb on the bottom and 3 3/4 lb on the top, and the scope balances perfectly with a 1 1/4" diagonal and large eyepiece. If I put on the dew cap, I use 10 lb on the bottom and 12 12 lb on top, and again I get absolutely perfect balance.

The rail system is so strong and solid, I could do chin-ups on it. I can replace the "Z" bracket and weights on top with a straight 2-hole strut bracket and attach my guide scope, which is an old C-90, in their place.

If I need to slide weights forward of the bracket, I can remove the hex nut on one end of the strut, and slide in a big bolt-washer-wing nut arrangement that I can attach weights to and slide it easily anywhere I need it, backward or forward, up or down. But so far, all the weight has stayed behind the brackets. The weights remove easily by loosening the bolt that attaches the "Z" bracket to the strut, and removing the "Z" bracket with weights still attached.

This is such a good, solid, strong sliding weight system, I can't believe I would have had to pay $500 for the same thing from a commercial vendor, and probably not gotten nearly as good a setup. I hope some of you try this; I am absolutely delighted with the way it turned out.

Return to Members Products & Design page or Return to 2-D Counterweight Design pageTop Button