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DIY Dob bases?


GordonCopestake
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Does anyone have any experience making dob bases? I've recently purchased Nick Smith's SPX200 and need to go about creating or buying a dob base. If anyone has any plans or photos that would be grand.

I may just take the easy route and purchase an Orion Optics dob base, but they cost £210 and it seems a little steep for 3 pieces of metal and a bit of PTFE!

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Antares do a complete kit including base, side bearings etc.. I got my brothers one from james and maria at scope n skies.. it took a while to get here but its a good piece of kit.

If your making your own it might be worth buying the side bearings from them anyway as they are shaped to fit the tube and come with the spring tensioners and hardware which does make a difference.

If building the base yourself then use good quality birch ply with marine varnish on the exterior to protect it from the damp.

I think the whole kit from james came out around the £100 mark inc delivery.

Also Antares are now doing a cradle that will take an OTA and whilst allowing it to be mounted as a dob still allow the tube to rotate..Thats a definate bonus.

It also might be worth having a word with CC to see if he fancies knocking you up an alloy base, if he has any metal left..

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Hands full? I don't know what you mean. :)

The ali has all but gone Ian, as it was actually paid for (very unusual for me), maybe enough left over for the sled focuser and I feel bad about that as it was Gordon's link that pointed me that way.

Bodging time now, looking at the OO setup.

The base bit has two pads per side which are the bits that touch the 'scope bearings. So why does the cutout have to be round? Answer it doesn't. Simplify it to a vee cutout and you still get two point contact each side.

Round bits on the 'scope could possibly be made from a plywood cable reel available for free if you find one. Stick some iron on edging round it and it could work, glue on some worktop edging and that's the "standard" way to go.

I'd make sure that the long Newt. will clear the floor in an off the shelf Dob. setup, but I guess that you knew that anyway Gordon.

If any of you guys want to play with my DIY toys, you're welcome to pop by and have a play.

Captain Chaos

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You're right about the V shape CC rather than the semi-circle. I was looking over the original Dobson plans and he uses a V too. Although i'll try and use the same piece of wood rather than glue an extra bit on in his design. Hmmmm give me an hour with Corel Draw and i'll try and whip up some plans :) Then you can all critique them for me heh

Astroman, i'll take a look at your website and see if i can glean any info :)

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A trip to my local Focus DIY store reveals that a sheet of 19mm MDF is £15, whilst a sheet of planned pine timber is £25. Bizare. If i go to block and quale with my cutting list they'll cut it too. Which is nice. I think im going with 4 600x600 planks screwed together with the base board sliding on an old vinyl lp, i knew they'de come in for something! The V shape then gets cut into the sides and some PTFE pads stuck on. Done! Seems easy enough.......

Not sure how im going to attach the bearings though, and i might have to change the heights after i have the scope as i have no idea where the balance point is at the moment.

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Gordon

If you're thinking of using MDF I suggest you specify 'moisture resistant grade' if you can get hold of it.

(It's used for flooring in most new houses as the floors can be open to the elements until the roof goes on)

Good luck with the project.

MD

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OK whilst mooching around in my shed i came across a 300mm wide kitchen cabinet that we had left over from when we kitted out our utility room. As the SPX200 is 200mmish in diameter i had a brain wave and considered converting the kitchen cabinet to a dob base. It's worked rather well but i think i need to find a larger base board. The current base board is an offcut of kitchen work surface (i thought the surface might provide enough friction). I need to investigate a larger base and a good bearing (teflon maybe) but for now i think it looks great for about 30 seconds hacking!

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Don't you just love the serendipitous discoveries when stuff you have that you thought was junk becomes an integral part of your new masterpiece?

You might want to investigate what would be involved in narrowing it to suit the 'scope, it might be dead easy, then you don't have to pad out the sides to fit the cupboard. Or you can cut the vee and glue on some 50X20 strips on top of the vee cuts to bring the sides in that way.

Looks just the Dob. er job Gordon.

Captain Chaos

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Thanks CC. According to the OO website the SPX200 is 232mm in diameter. The cabinet is 300mm outside with 20mm sides which gives about 260mm inside. Minus the 232 this gives me about 14mm clearance either side. In my mind thats ideal :)

Block and Quale should make Dob bases hehe

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If your making a box section for the tube you could use sections of 4" or 6" plastic drainage pipe glued and screwed to the box section. If your worried about flexure on them then cut a wooden disc to fit inside the pipe section and glue both together. That should give you a nice ride for the OTA..

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You've inspired me to mess about with my little 114mm reflector and I will be doing as you are in keeping the rings..Ive decided on plastic pipe filled with a wood disc for mine.. Just have to hunt in the local skips for some wood etc now :)

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Until I sold my 4.5" OTAs, I was thinking of making a Dob base, using ABS end caps for the pivot, and sections of ABS tube for the bearings. I have some teflon, but it seemed to me that the ABS would work just as well.

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