Collapsible Dob Base DIY For A Lightbridge 16
Posted 12 November 2012 - 01:49 PM
I spent last year modifying the telescope itself. Check that out in this thread on the overhaul of my Lightbridge and birth of "M42" . Now it is time to redo the base.
My goals are to increase the strength and durability, decrease the weight, and diminish the over all size from the stock press board base. I also wanted to make the base completely collapsible. This will make it even more portable. If you aren't aware the original base on the LB16 is huge, hard to fit through doors, and a beast to haul around. The stock base has worked well for me so far and has held up well. I usually just haul it in and out of the garage on a JMI cart. I did modify the stock base some by chopping the top off making it shorter so it would fit in my Kia Soul better. I also increased the bearing cut out diameter by 1/4" to allow for PTFE/ebony star. The stock base has served me well, however, it is time to go.
I was motivated to do this project since I have an eq platform being made for me right now. The eq platform will replace the ground board. The new platform also means I will be switching to PTFE pads and an ebony star azimuth bearing from the original roller bearing set up. Rather than just add the ebony star to the bottom of the stock rocker box I decided to redo it entirely.
Stay tuned. This is going to be fun.
Posted 12 November 2012 - 02:02 PM
I took time at the hardware/lumber store to tape the top and bottom of each cut to prevent splintering. This attracted a few looks but was well worth the extra time.
The store has a wonderful panel saw that made short work of the 3/4" Baltic birch plywood board. They made all the cuts for me and for free too. The board was cut to exact size fast. It was way easier than doing it in my wood shop. Taking home the cut pieces was easier than the 4' x 8' board also.
Posted 12 November 2012 - 02:11 PM
Your new base mated to the EQ platform is going to be an awesome setup!
Posted 12 November 2012 - 02:17 PM
Everything is clamped and the circle jig is then lowered onto the pivot pin at the correct hole for the size I am cutting and the cut is made. I took a couple plunges at it to ease the bit's burden.
Reproducing these cuts was fast and easy for the next three side pieces.
Posted 12 November 2012 - 02:24 PM
Once again I placed the router circle jig on the pin and in no time the shoulders were cut. I used a 1/4" straight bit in the router. The other three sides were cut in short order and all were exactly the same.
Cutting the shoulders will lighten the side pieces and gives some aesthetic charm. I was able to shorten the height of the side pieces to 19" overall but the bottom of the bearing is exactly the same height as the stock rocker box.
Posted 12 November 2012 - 02:36 PM
Next I marked center on the ground board pieces and drilled the 1/8" hole for the router circle jig pivot pin. The pin was placed in the drilled hole and the correct hole on the jig was chosen.
In no time at all I had two ground boards. I know I told you I am ditching the ground board with the eq platform. However the base I sell will need one. I plan on recycling all the original Lightbridge base's hardware so the new owner can just attach all the original stuff to these parts. I also figure that it is so easy to make one for myself now that I would. That way I could have the option of not using the eq platform and just having a regular ground board if I choose. Why would I choose that? I don't know. I have a router and it is fun.
Posted 12 November 2012 - 02:38 PM
Posted 12 November 2012 - 06:01 PM
Posted 13 November 2012 - 09:05 PM
Today I was back in the wood shop playing. I started by making a jig to help me router the shape for the knob cut outs. I over cut the shape from the scrap plywood I was using.
Everything square and tidy.
Next two cleats were added to the bottom of the jig. The side and front panels will fit in the corner made.
Posted 13 November 2012 - 09:17 PM
Next the piece is pressed into the guiding cleats on the bottom of the jig and is instantly squared and positioned. Everything is then clamped.
Finally the router makes the cut. It sits in the jig cut out/guide and follows the outside. I plunge in steps taking a little more wood out with each pass. This spares the bit and makes it easy going. By using this jig I can repeat shape and placement exactly on each cut. The panel is then turned over and the opposite corner is cut in the same way.
Posted 13 November 2012 - 09:28 PM
Finally two side panels with the knob cut outs are done. As you can see the jig makes the shape repeatable and exactly the same on all corners. I went into production and cut the rest of the sides and fronts. These cut outs will hold the knobs that mount the sides to the base.
The circle cutting jig came back out and I made an 8" hole to lighten the load even more. Again plunging gradually keeps it all tidy and nice. I suppose the cut outs will help with air circulation around the mirror although minimally. The circle cut outs will also window the telescope base so it can be seen since it is so pretty.
Posted 13 November 2012 - 09:35 PM
Here you can see all four side panels together with all the cuts finished. They are all exactly the same with amazing accuracy. I am pleased.
The front piece also got its own circle cut out to save weight. You can also see the knob cut outs. They are like the side panels and were cut with the jig I made too.
Posted 13 November 2012 - 09:44 PM
I test fit it all together with some masking tape. Side by side with the stock base you can see the marked difference in size. The stock base I have has already been shortened a couple inches in and earlier modification so the over all change is even more dramatic than these pictures show.
I weighed the cut outs and all the scrap that was cut from one base. The scrap was over 5 lbs making it that much more lighter. I haven't weighed the entire new base yet. I thought I would save that until the end. Finishing and hardware will change things. Still, this new base is so much lighter and stronger it is shocking. I am well pleased with today's progress.
Posted 14 November 2012 - 09:58 AM
Posted 16 November 2012 - 05:31 AM
Posted 16 November 2012 - 07:17 AM
Posted 16 November 2012 - 11:14 AM
Brian-the jig is a Jasper Circle Jig Model 200 and can cut circles up to 18 3/16". I modified it a tad (duh, I modify things) by drilling some holes on the edges so I can make up to a 19 3/4" circle. The ground board for the base is that big. It works like a charm. I recommend it highly and it is less than $50.
Posted 16 November 2012 - 11:36 AM
Nice progress so far!
Posted 16 November 2012 - 04:15 PM
Brian-the jig is a Jasper Circle Jig Model 200 and can cut circles up to 18 3/16".
Posted 16 November 2012 - 10:44 PM
Sean - How are you? Great to hear from you. I have some cool ideas about matching the base to the scope. You know me. I am full of surprises.
Hey Doc I'm going good mate. Haven't done too much more to the Lightbridge II since the last thread - just some minor tweaking, and adding all the bumps and scrapes that go with a well-used scope. Interested to see how you go with the equatorial platform - after all, I blame you for making me go buy that space-age fan on the back of my scope! Am saving my power tools and patience (and pennies!) now for cobbling together something big!
Posted 19 November 2012 - 05:34 PM
Most of my time this weekend was spent cutting strips and pieces of laminate. I am over cutting all the pieces to allow for trimming with the router. I was going to use the router to cut the strips but found that I was loosing too much to the router's cut. I decided to use a pair of tin snips instead. This is not the preferred way to cut laminate but works well enough. There is a risk of breaking and ragged chipped edges this way and indeed I had a few strips and one big piece do just that. However, the amount of scrap generated from the odd breaking was no where near the amount I would have lost using the router. I am happy I have the third piece of laminate as a cushion. Over cutting allowed for the odd ragged edge as well. This will be cut off once glued and the laminate is given the final router edge.
In the second picture you can see all the pieces cut and waiting for glue. I thought the cutting would be faster than it was. It takes time and is tedious. Rushing caused breaking and chipping. I was forced to a slow steady pace. I also have to warn you that the first rule of handling cut laminate is WEAR GLOVES! It is a shame that it took me five or six cuts to my hands to come to obey this rule. This stuff does not care who you are. It will cut you.
Posted 19 November 2012 - 05:58 PM
I started with the inside radius circles and cut outs. After each strip and its corresponding panel edge was dry and tacky it was placed. The circles were a breeze. I started by rolling up the laminate smaller than the hole and tacking one end down. This allowed me to fit the looped laminate inside the circle cut out and work it smoothly to the end. I put the joint at the top to hide it best. The cut outs were a bit trickier. The rounded edge I chose looks great but is a pain to get laminated. The radius was too small for the laminate to roll up like I had done with the circles. Sneaking each curved piece by with out having it come in contact with the plywood edge was a tough job. I cracked several pieces and had others attach prematurely. Once this stuff comes in contact with the other side it cements. The name contact cement is so appropriate. I got the hang of it and only had one curve needing chiseling of a broken strip and regluing. Again, the rule of thumb here is have several pieces standing by in case of a snap. It was way easier throwing out a couple as scrap than not having them. I only had a mild case of transient Tourette's Syndrome placing these pieces. The straight pieces were a breeze comparatively.
In the third pic you can see the pieces I got done this weekend all lined up and waiting for the router. I will let the cement cure before the router so I don't gum up the bit. I figured this out after routing the round ground board edge. They are leaning up against the wall in the back. I went ahead and routed them. They look great but the bit needed some TLC with the mineral spirits.
Laminating is a slow tedious process. I am beginning to understand why people choose urethane instead of laminate.
Posted 19 November 2012 - 10:17 PM
GOOD JOB AND KEEP IT UP!!!
Posted 26 November 2012 - 11:36 AM
Both bases needed about a half gallon of contact cement combined. My wife said that it smells like anesthesia.
Rolling with pressure is important to get the pieces to adhere with maximum grip. This laminate isn't going anywhere.