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Collapsible Dob Base DIY For A Lightbridge 16

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#1 Project Galileo

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Posted 12 November 2012 - 01:49 PM

It has begun.

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.

#2 Project Galileo

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Posted 12 November 2012 - 02:02 PM

First, the plans. Okay, I am not big on plans and usually just make it up as I go. This shows how I taped up the plywood for cutting however. I fit the project on one piece of Baltic birch. There was enough for two bases. When I am done, I will sell the other.

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.

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#3 Gastrol

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Posted 12 November 2012 - 02:11 PM

Your original M42 thread actually inspired me to start modifying my Lightbridge 12. That thread is well worth the read for any LB owner.
Your new base mated to the EQ platform is going to be an awesome setup! :)

#4 Project Galileo

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Posted 12 November 2012 - 02:17 PM

Next I made a jig for my router's circle cutting jig. The circle cutting jig has hundreds of holes allowing me to make perfect circles every 1/16th of an inch. I marked center on the jig I made, measured then drilled and placed the jig center pivot pin such that when the side piece was centered to the jig the altitude bearing cut would be centered and also exactly the same height from the ground.

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.

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#5 Project Galileo

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Posted 12 November 2012 - 02:24 PM

Some fast geometry helped me drill the perfect spots for the router circle jig center pin. These holes will be the center for cutting the side piece shoulders. They also will get cut out when I make the center circle cut out later keeping it all tidy.

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.

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#6 Project Galileo

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Posted 12 November 2012 - 02:36 PM

In the first picture you can see just how exact and uniform the four side pieces are after the altitude bearing and shoulder cuts. Isn't precision beautiful?

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.

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#7 Project Galileo

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Posted 12 November 2012 - 02:38 PM

Gastrol - Thanks for the props. You are making a fine base yourself I see. Well played. Knuckles and all that stuff!

#8 Aperturefever

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Posted 12 November 2012 - 06:01 PM

Cloudy nights in the garage can be such fun ... you'll find life so much easier with a new base, believe me. Now how in the world are you going to match the base colour scheme with that snazzy tube?!

#9 Project Galileo

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Posted 13 November 2012 - 09:05 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.

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.

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#10 Project Galileo

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Posted 13 November 2012 - 09:17 PM

The jig fits over the panel to be cut. You can see the side panel to be cut at an angle with a drawing of the desired shape on it. The drawing is unnecessary since the jig makes things automatic. I just drew it there for the pic.

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.

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#11 Project Galileo

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Posted 13 November 2012 - 09:28 PM

A file is used in the corners to sharpen them up. The router bit is a 1/4" straight cut and leaves the slightest curve in each corner. The file perfects the intended shape.

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.

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#12 Project Galileo

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Posted 13 November 2012 - 09:35 PM

Hole production kept me busy for another 20 minutes. The circle cutting jig is the bomb!

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.

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#13 Project Galileo

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Posted 13 November 2012 - 09:44 PM

All the cutting is done and the saw dust has settled. Both bases are now awaiting finishing.

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.

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#14 Project Galileo

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Posted 13 November 2012 - 09:46 PM

PURDY!

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#15 Bill Kocken

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Posted 14 November 2012 - 09:58 AM

Two thumbs up. I can smell the sawdust just by looking at it!!

#16 Scanning4Comets

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Posted 16 November 2012 - 05:31 AM

Looking good! This new one will be a lot more sturdy than the original LB base! I'll be back to watch your progress! So far, I really like your scope & mods! :waytogo:

Cheers,

#17 starman345

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Posted 16 November 2012 - 07:17 AM

Its shaping up nicely. I have the exact same Craftsman router, what is the brand name of the circle cutting jig you are using with it?, how big a circle will it cut?

#18 Project Galileo

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Posted 16 November 2012 - 11:14 AM

Thanks guys. I am having fun with the project.

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.

#19 Gastrol

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Posted 16 November 2012 - 11:36 AM

It's funny how the stock base uses such small diameter azimuth bearings in relation to its huge ground board. Your new smaller diameter ground board with larger diameter contact points (I would assume) should perform better.
Nice progress so far! :)

#20 starman345

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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".


Thanks!

#21 Aperturefever

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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! :grin: Am saving my power tools and patience (and pennies!) now for cobbling together something big!

#22 Project Galileo

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Posted 19 November 2012 - 05:34 PM

I got to spend a little time with this project this weekend. I have decided on laminate vs. urethane or paint for these bases. I obviously want to seal up the wood against dew and humidity. I also wanted to add the most durability. Since these bases are made to be collapsed and transported I expect them to pick up more dings and scuffs than the average base. I want to protect them from the little stuff. Further, I want to match the flat black of the powder coating on the telescope. I special ordered a Wilson Art flat black laminate and had it delivered to the local hardware store. It arrived three days later and I got a call to come get it. I ordered 3 sheets of 4' x 8'. I will have some left over since I will only need a few cuts from the third sheet.

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.

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#23 Project Galileo

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Posted 19 November 2012 - 05:58 PM

The next step was contact cement. In the first picture you can see the contact cement drying on the backs of the laminate strips. I also applied the same glue to the surface of the plywood to be bonded. I found that I had to apply two heavy coats to the end grain of the plywood to get the correct tackiness. Waiting 20-30 minutes in between coats and for the strips to dry proved to be the magic number for me this weekend.

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.

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#24 whirlpoolm51

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Posted 19 November 2012 - 10:17 PM

Nothing is funner than playing with a router and all the awesome tools that come along with our scope projects...and also the bumps,scraps and bruises!! but its all worth it just for the sweet smell of sawdust hahaha

GOOD JOB AND KEEP IT UP!!!

#25 Project Galileo

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Posted 26 November 2012 - 11:36 AM

This weekend I spent more time laminating and trimming laminate. The inside circles proved to be a tad tricky. My router would not fit inside the curves. I attached a fence out of scrap wood to lift the router and then used a flat edged bit adjusted to make the edge pieces flush. It worked quite nicely.

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.



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