ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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new LB16 base -- look Ma, no weights!
#5292571 - 06/28/12 12:30 AM Attachment (186 downloads)
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I set on an adventure to build a new base for my LB16. The primary goal was to make a base that could fit in my Prius so that I can get 50MPG going to my dark site rather than 23. Secondary goals were to eliminate the need for counterweights and to hopefully improve the motion of the scope over the stock base. If it came out significantly lighter that would be nice but it wasn't really one of my goals. A must was that it had to be sturdy.
I started on this project on my break between Christmas and New Year's and the fact that I'm not much of a wood worker surely caused the project to drag out. To be honest I'm not really don't yet either -- I still have some finishing to do. This last New Moon cycle I did get it to a useable state however and I can say that I am pleased.
On the blistering hot afternoon (108 degrees or something close to it) of June 16th I got the new base to the state where I was able to load it into my Prius and drive for an hour or so up to some darker skies. I arrived at Blue Canyon just before sunset, set the scope up, and had a wonderful evening. Unfortunately for the first time ever I didn't have time to create an observing list so I just went for some old favorites but I was able to enjoy the new base.
While I did meet my primary objectives, as it currently stands I need to remove the trunnions for it to fit in the back of my Prius standing up. I need to decide if I'm going to live with it like it is and remove them every time (4 bolts each), lay the LTA on it's side while transporting, or sacrifice a bit of the altitude rotation to shorten it up. (I would probably lose about 10 degrees at the horizon -- so I won't be able to look at Omega Centauri.)
I did achieve my goal of being able to go from an ortho to a Paracorr+Terminagler with no additional counterweights. There is just enough static friction to allow use of either extreme at any angle with no drift. I've never used a premium scope so I have no point of reference but I'm pretty sure that while the movement is nice and smooth and better than stock, it still isn't like a premium dob.
There is no doubt that it came out sturdy. Heck, I could probably rest my Prius on it. As for weight, I shed a few pounds from the stock scope but not enough to make a huge difference. If I had to do it over again, I would do things a bit different and it would definitely come out lighter. That said, I'm not unhappy as dramatic weight drop was not a major goal. Perhaps when I build an EQ platform I'll redo the base using the knowledge that I've acquired so it will be lighter. (And I'm sure I could do the base portion in a fraction of the time.)
Okay, enough talk -- I'm sure you want a picture. Here's one with a BGO. As you can see, I still have some staining to do...
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look ma, no weights!
[Re: ThreeD]
#5292572 - 06/28/12 12:31 AM Attachment (130 downloads)
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Here is one with the other upper end weight extreme -- a Paracorr and and a 31mm Nagler.
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Aperturefever
super member
Reged: 12/12/10
Loc: Lake Macquarie, Australia
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Re: new LB16 base -- look ma, no weights!
[Re: ThreeD]
#5292597 - 06/28/12 01:17 AM
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Well played Scott ... I was wondering when you'd get this job done! You're doing better than me - I still need my Farpoints on the back. Curious to see a tight shot to see how you've got it attached to the tube. I'm sure, like me, you'll have an even better time out under the stars.
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look ma, no weights!
[Re: Aperturefever]
#5292638 - 06/28/12 01:53 AM Attachment (96 downloads)
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Yes, I must give credit where credit is due. I thought that I might be able to utilize some of my physics and engineering mechanics classes (though I'm not an ME) to design a bearing/base that would let me achieve the goal of losing the counterweights. Clearly I found validation of the idea on the web and without that I might not have taken the time to actually make a base.
I chose however to remove the aluminum trunnion and completely replace it rather than build around it. Doing so allowed me to have a bit more fun with a router as well. Here is a top view...
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look ma, no weights!
[Re: ThreeD]
#5292645 - 06/28/12 02:01 AM Attachment (84 downloads)
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Now for a side view. The four holes on the upper and lower (curved) pieces are where the bolts that attach the trunnions to the tube pass through. There are nuts in the interior of the wood part that the bolts screw into. The four screws on the side pieces attach the trunnions themselves to the wooden bracket. By moving the bracket up and down along the trunnion I can adjust the rotation point and thus adjust the balance of the scope. I seem to have nailed it the first time and got the correct location.
One of the things I would do differently if I did it again is I would buy the next size smaller ebony star bearing ring. I was concerned that due to the weight of the scope I should error on the side of caution and use the larger ring. I now think the smaller ring would have been fine and that would have allowed me to make the base two inches narrower and eliminate the standoff portion of the brackets. The base would also be smaller and thus lighter. (There are other things I would do differently next time which would further reduce the weight.)
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look ma, no weights!
[Re: ThreeD]
#5292652 - 06/28/12 02:08 AM
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Oh, and a major factor for the length of time the construction took is because my children are in sports and I feel it is important to attend my childrens' games. My daughter plays in a large number of AAU basketball tournaments and when my son is doing Little League that tends to take a few hours here and there. Then there is always my job... clearly astronomy related activities take a back seat as well they should.
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Darenwh
Carpal Tunnel
Reged: 05/11/06
Loc: Covington, GA
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Re: new LB16 base -- look ma, no weights!
[Re: ThreeD]
#5292791 - 06/28/12 07:37 AM
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Great job. You achieved all your design goals and it looks decent also. Very well done and putting your family first is by far the best thing to do.
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Project Galileo
professor emeritus
   
Reged: 11/14/07
Loc: Jefferson County, Colorado
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Re: new LB16 base -- look ma, no weights!
[Re: Darenwh]
#5361566 - 08/10/12 11:40 AM
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Look's great!
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BDS316
Carpal Tunnel
Reged: 09/16/09
Loc: Sol 3
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5364595 - 08/12/12 11:36 AM
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Nice work. Does the scope have any lateral drift in the mount and if not what did you do to prevent it?
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look Ma, no weights!
[Re: BDS316]
#5365802 - 08/13/12 01:48 AM Attachment (45 downloads)
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Thanks for the comments. I'm about to trim the tips of the trunnions off so I don't need to remove them to fit the LTA standing up in the back of my Prius. I'll end up removing enough so that I won't be able to dip below about 12 degrees above the horizon. That's okay -- I think I've only gone below that once anyway in order to see Omega Centauri (at less than 5 degrees probably) and it wasn't much of a view. 
To prevent lateral shift I put four small pieces of aluminum strips on the inside near the teflon. I imagine one on each side would be sufficient but I feel better with two. I bent the tops of the strips a bit so that when I set the LTA in place they will help guide me to the correct placement and also to minimize the surface area with which they make contact. As you can see from the picture I still need to stain the trunnions (which I'll do after I cut the tips off) and I also need to work the aluminum a bit so the screws will be countersunk. (Again, I was in a rush to get this base usable and haven't had time to finish the work -- something that always gets more difficult once something makes it to the usable yet unfinished state.)
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Scott in NC
Mad Hatter
   
Reged: 03/05/05
Loc: NC
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5366858 - 08/13/12 04:47 PM
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Very nice job!
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Gastrol
scholastic sledgehammer
Reged: 11/04/11
Loc: los angeles
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Re: new LB16 base -- look Ma, no weights!
[Re: Scott in NC]
#5366889 - 08/13/12 04:58 PM
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Indeed, very nice mount! Eventually, I'll construct a new base for my LB-12, but in the meantime I've extensively modified the stock base by reducing the oversized ground board, trimming the side boards, alt bearing mods, and adding a degree circle. It is a much better mount now.
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yonkrz
scholastic sledgehammer
Reged: 11/16/06
Loc: SW Minnesota
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5368393 - 08/14/12 01:42 PM
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Pretty awsome upgrade,Scott.
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look Ma, no weights!
[Re: yonkrz]
#5476136 - 10/18/12 12:19 AM
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Minor update. I cut off the forward/upper portion of the trunnions so it wouldn't be as tall. It will now fit in my Prius without removing the trunnions from the LTA which will save time and hassle.
I also applied a little SailKote to the ebony star. Man is it buttery now. The movement is really incredible and I still have no balance issues even if changing from minimal to extreme glass.
I may try to remove some of the wood in the base to lighten it up soon. I'll post pictures when I'm done.
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bilgebay
Post Laureate
   
Reged: 11/06/08
Loc: Türkiye - Istanbul and Marmari...
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5476295 - 10/18/12 03:00 AM
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Sailkote is incredible indeed. I remember me mentioning the product in one of the threads on CN a while ago but apart from that you are the second person ever I see mentioning it here
It is good for everything that moves and slides. But not for ball bearings. For that there is another product from Team McLube.
I may follow your route to mod my LB16 as I am not so happy with it as is. Thanks for sharing your great ideas.
Cheers
Sedat
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Project Galileo
professor emeritus
   
Reged: 11/14/07
Loc: Jefferson County, Colorado
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Re: new LB16 base -- look Ma, no weights!
[Re: bilgebay]
#5719735 - 03/08/13 12:47 AM
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Scott, how are things with the new bearings? I was wondering how they have been working for you. Would you make any modifications in design? Mods to the center of balance?
I ask because I am considering building a similar set of bearings for my LB.
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look Ma, no weights!
[Re: Project Galileo]
#5719787 - 03/08/13 01:59 AM
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The motion and balance is fine (though I must admit I've never used a premium dob so I don't really have the best point of reference). I just know I have no problem making small movements at high power and I never need counterweights. The balance is good enough and there is just enough stiction to hold the scope at any angle whether using a lone ortho or a 31T5 with a parracor.
The only changes I would make have to do with dimensions and a few things to reduce weight. Weight reduction was not a primary goal so I concentrated on balance without counterweights and on making it rigid. Not being a woodworker I had no idea of just how stout it would end up so I erred on the side of overkill. Wow is it stout.
I used 25mm ply whereas I probably would have been fine with 19mm. This alone would have dropped the weight by 25%. Cutting some holes/openings in the sides and the front would have dropped weight further. Again, I'm not really a woodworker so I was challenged enough just to get something made that functioned and looked reasonable. Now that I've done it once I would feel more comfortable doing the extra work to lighten it up.
I was split on the size of ebony star ring to use. The supplier I used has a 20.25"OD ring that it suggests is for 12"-16" scopes and a 23.5"OD ring that it suggests is for 16"-20" scopes. Since the LB is not a lightweight scope for its size I figured I should go with the 23.5"OD ring which means I made the base 24" square. I have feeling that I would have been fine with the smaller ring and a base more like 21" square.
In the end I'm very happy with what I actually have so the changes aren't what I'd consider musts. It's more portable than the stock LB base and I have the benefit of much better motion with no balance issues.
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coopman
Carpal Tunnel
   
Reged: 04/23/06
Loc: South Louisiana
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5719961 - 03/08/13 07:52 AM
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Looks nice. Glad that you were able to get rid of the tube balance issues - the large dia. trunnions with the widely spaced teflon bearing pads is very helpful towards that end.
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ThreeD
scholastic sledgehammer
Reged: 12/23/08
Loc: Sacramento suburbs
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Re: new LB16 base -- look Ma, no weights!
[Re: coopman]
#5720169 - 03/08/13 10:01 AM
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Those affect the movement. Moving the point of rotation up a few inches fixes the balance. The center of the new trunnions are a bit closer to the eyepiece than the stock ones.
I think the stock scope is actually pretty close to balanced as it ships but as soon as you replace the RDF with a RACI, add a shroud, or use an eyepiece that actually has some mass then you are nose heavy. Do all three and you need someserious counterweight. It's amazing what moving the bearings a small amount (about 1.5" if I recall correctly) will accomplish.
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Scott in NC
Mad Hatter
   
Reged: 03/05/05
Loc: NC
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Re: new LB16 base -- look Ma, no weights!
[Re: ThreeD]
#5722370 - 03/09/13 01:44 PM
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Nice work, Scott!
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