Dob mount build!

[Mark-mck]

that's tip top.

going to have to think about building one myself in a few months, mount will be required for an apo at some point but i'm never getting rid of the 250, its a beast.

[rawhead]

That looks great

[Bigdaddyjeff]

This looks excellent! One point to make is that the 'best' design is to have any bearing points in the base on top of each other. You may find it will be smoother with the casters fixed above the feet?

Other than that it looks superb and should work really well.

I did contemplate putting the castors directly above the feet but settled for an equal space....will see how it goes where they are but if it's not so great i'll move them again...thanks for the advice and kind words though

Thank you all for your kind words and encouragement too and mick...this 250 certainly is a beast...and when i get the money together for the neq6 i'll be in the fortunate position of having 2 mounts to choose from as you will be when you start YOUR build

Gaz

[Moonshane]

no worries Gaz

It was not a criticism BTW as you've done an excellent job. the reason for it is that all the weight bearing down on the erm bearings, is all then into the ground through the feet rather than into the board. I reckon with the scope you are using it with is will be fine though as it's not that heavy.

[Bigdaddyjeff]

No that's fine mate,didn't take it as criticism at all...i appreciate all input on it anyway

I'm a little worried about having the scope up vertical (zenith i think it's called:icon_scratch:) and the scope slowly sliding out of the cradle ....so i was thinking of maybe 2 thin strips of 6mm ply running off the cradle adjacent to the tube towards the rear of the tube then another piece attatched to these to act as a kind of seat for the tube once vertical?? What you think?? Does that even make sense??

Gaz

[Moonshane]

hi Gaz

I see what you mean. I am not sure what angle you set the side bearings at in relation to the top edge of the cradle but the recommended angle is 30 degrees. could yours be more like 45? if you didn't glue and screw the side bearings (I fear you probably did) then you could refix then at 30 degrees. if you did glue them, then you could make another segment of the same radius as the current bearings and then fix this to the top rear of the cradle and this would then solve your problem?

[Bigdaddyjeff]

hi Gaz

I see what you mean. I am not sure what angle you set the side bearings at in relation to the top edge of the cradle but the recommended angle is 30 degrees. could yours be more like 45? if you didn't glue and screw the side bearings (I fear you probably did) then you could refix then at 30 degrees. if you did glue them, then you could make another segment of the same radius as the current bearings and then fix this to the top rear of the cradle and this would then solve your problem?

Didn't glue them so if i needed to make any adjustments it would be easier to do so. You'd be correct in assuming the 45dg angle so i may just give a session a go at what they are now then adjust or leave alone accordingly...thanks very much

Gaz

[Moonshane]

no worries. I reckon at 30 degrees you'd need to do nothing else should be spot on.

I think you'd done an excellent job on this.

I have an 8.5" f8 mirror set and I'm going to make a truss dob from this as a travel scope so it's great to see different people's designs. I am going to make a jig to allow me to create finger joints which I really like.

[swamp thing]

Nice job Gaz

Done yourself proud there.

Regards Steve

[ponytale]

hi bigdaddyjeff been watching your post with interest , great job !!!, one of your post you seemed concened about the ota sliding , if you make a couple of end boards for your cradle with a hole to fit your tube size, cut it in half and line the curved edge with felt, fit a hinge/pivot at the joint on one side and an adjustable tensioner on the other do this both ends of cradle with a knobbed bolts to fix the boards to the cradle , you will have a sort of wilcox ring setup which allows rotating the scope in the cradle without it being loose enought to fall/slip . hope this helps Tony

wilcox plates.doc

[Bigdaddyjeff]

Thanks Steve...much appreciated

Thanks too Tony and I think i can picture what you're describing. I think my problem is i've built the mount as a temporary measure until I can get the NEQ6 for the scope and i'm scared of tightening the cradle too much and damaging the tube.

Gaz

P.s Thanks for the link Tony

[MoonNut]

This is a great thread, I have just done the same thing for my LXD55 and for exactly the same reason as you, BigDaddyJeff!

ImageShack® - Online Photo and Video Hosting

ImageShack® - Online Photo and Video Hosting

I designed all the sections I needed with Turbo Cad 4 and took it to a local woodwork shop. They cut the pieces I needed and painted them "satin black" so all I had to do was assemble them.

Wood is very expensive here so as a trial I used 1/2" MDF, and it seems to be strong enough. I do not have facilities to cut an accurate straight edge either.

I used "Magic Sliders" for both Alt and Az bearings and they work very well. These were probably the most expensive parts.

I believe it works well enough although I have found it to be a little bit too low as I find myself struggling to get down to the eye piece.

I understood that one of the main problems with the bearings is over coming the "sticktion" when strting to move the scope, I think the magic sliders do a good job but I have nothing to compare it with!

The total cost for the MDF sections (painted) was £16 all the other hardware around £25.

I will be posting a more detailed thread soon.

[Bigdaddyjeff]

Very impressive indeed MoonNut... all done within a very impressive budget too. I've yet to get mine outside for test run so will see how I get on with the viewing height

Gaz

[MoonNut]

Gaz,

I was trying to make it as compact as possible, didn't even think about the viewing position

I thought for a long time about the "cradle" before I decided to use the original tube rings, I thought the method you have used would make the whole thing a bit too wide and cumbersome while at the same time I thought attaching the alt bearing to the rings via a steel plate with only one bolt at each end would not be strong enough (the OTA is heavy) or that it may move under load, surprisingly it is very solid. I can pick up the scope by one bearing mount!

I have taken a series of pics during each stage of the build, you will be able to see what I am talking about above when I post them later today or tomorrow.

Very interested to see yours completed, (I think this is the best thing about forums like this, I don't think I could list all the things I have learned or even passed on)

David B.

[sandspider]

Very inspirimng, I'n a newbie but I think I could build that. Fingers crossed

[captainlee]

Great job like your turn table design.