How hard is it to build a telescope?

[gooseholla]

Oh where do people get those foam pipe insulators from? Biggest I can find is 22mm or 28mm but my poles are 32mm?

Thanks

John

 

[mapstar]

Oh where do people get those foam pipe insulators from? Biggest I can find is 22mm or 28mm but my poles are 32mm?

Thanks

John

What about the heat shrink route John?

[gooseholla]

What about the heat shrink route John?

I was having trouble finding heat shrink at a reasonable price and the pipe insulators seemed cheaper. However, I have found this at £14.75 for 10m of  black 41mm diameter 2:1 shrink:

http://www.ebay.co.uk/itm/PVC-Heat-Shrink-Tubing-Wrap-RC-Battery-Pack-17mm-150mm-LiPO-NiMH-NiCd-UK-/361275492238?var=&hash=item541db2878e

I assume this will work fine?

John

[mapstar]

Looks like a decent buy. Not sure about the wall thickness of 0.1mm may not be that durable in the long run.

The stuff I used before has a wall thickness of about 1 mm

I was looking at this stuff item number 191203370320

Damian

[gooseholla]

Looks like a decent buy. Not sure about the wall thickness of 0.1mm may not be that durable in the long run.

The stuff I used before has a wall thickness of about 1 mm

I was looking at this stuff item number 191203370320

Damian

Thanks. Still exploring options. I think though it be pretty redundant with a shroud on anyway? Fortunately, el goosey is pretty handy with a sewing machine, but since my mum used to make clothes and bits, I might get her to make it in exchange for some wooden storage boxes ;-)

John

[swamp thing]

Pipe insulation starts to fall to bits quite quickly when handled a lot TBH John. I'd spend the extra few quid on the heat shrink myself.

Like the baffle and dust cover. Finishes off the box nicely.

[gooseholla]

Well my spandex/lycra is on the way for the shroud. I saw a really cool idea on one shroud site of using a bit to make a dust cover for the secondary cage. Might give that a go, as when its in storage it has nothing over it at the moment. It does mean the offcut can't be used for observing pants though  

What have I done this weekend? The Telrad was mounted to a plywood board so it is nice and secure now that it is working properly again. Cable ties to a pole just wasn't secure enough for me. Too easily knocked out of alignment. I also experimented with UTA clamping systems and will unveil my new ones within a week sometime, if all goes to plan. I plan on moving their position on the UTA when mounted, as currently when the scope is pointing to objects up to about halfway in the sky the eyepiece is too awkward for me. This will allow a more comfortable position for myself, being quite tall, to look straight down on it rather than having to crouch, bend and contort beside it.

I must say, just as an aside, that this type of dob is really sturdy. I can hold it and continually push it slowly keeping an object in view without any vibration, and a sharp slap to the dob dies down in just over a second.

John
 

 

[mapstar]

Look forward to seeing the results John

[swamp thing]

I must say, just as an aside, that this type of dob is really sturdy. 

John

You aint kidding mate. I reckon mine would double up as an engine hoist if needed. 

[gooseholla]

Today I did some tests with the UTA clamping systems. I played around with the wedge for a while, which is what I was going to build, but for my needs I think it will be to fiddly. The best I can come up with, and which my engineering neighbour likes the most is a rip off of the AstroSystems clamps. The poles go in the shed on the scope anyway, so they might as well stay together. Can plonk the cage down on top and let it stay in position, two turns of a knob locked in place. Will likely order cam levers for them to make it even quicker.

Will modify the one on the left to be my final design and make 4 nice looking ones out of proper ply, with a decent shaping job!

John

[mapstar]

The upper truss mounts are always difficult, and unless they are a copy its hard to come up with something of your own design that works?

I've changed the way I did mine from last time, it will take a little longer to construct but at least it give the mirror cool down time    (if I ever finish the thing!!!) 

Damian

[gooseholla]

I just don't like the methods of inserting a pole into an angled hole and clamping it. Both seem fiddly - wedge and my current method of a bar clamping across the front - and unless done real accurate are not that stable. I've had the poles start to slip a few times and that won't be fun if the cage drops! At least this way everything I need is bolted to something and never going anywhere. Think Astro Systems have hit the nail on the head for truss mounting system.

John

[tonylumley]

Oh where do people get those foam pipe insulators from? Biggest I can find is 22mm or 28mm but my poles are 32mm?

Thanks

John

have a look at the scaffolding companies, they use a foam cover for their scaffold pipes when in the pubic area, only problem is, they tend to be a bright yellow, still at least you will be able to find them when at a dark site, the foam would be about 2" or 50 mm fr you youngsters!!, you could ask at the local builders merchants John, or see the scaffolders opposite granddads in Heybridge, also try Travis  Perkins / plumbers merchants, as the large industrial heating installations are usually 32 or 50 mm pipes

[gooseholla]

Cheers Uncle T, will check that out.

Let me guide you through my UTA clamp method.

The back piece is 20mm Ash. I couldn't be bothered to go and buy some 18mm ply for one job and have huge leftovers. The front part is 12mm ply.

The knob is going to be replaced with a QR skewer. It sits in a channel in the D shape the poles attach to. This means I can plonk the cage down and tighten them all after.

It still needs a bit of refining but after that, tomorrow I will shove the pattern bit in my router and make 4 nice looking ones. Because I didn't want to copy Astro Systems completely my D is upside down compared to theirs.... what I mean is, stupid me wasn't paying attention and drilled the hole the wrong end! I like it better than two D shapes meeting though.

John

 

[mapstar]

Quick progress and looks good John.

[gooseholla]

Today I didn't get the chance to make the upper clamps. Before I could route, I needed to re-claim my workbench from a sliding mitre saw, so I built a stand for that instead. While picking up the wood, the lumber yard had a honking big bit of hardwood offcut the right size for remaking lower clamps. So I will do all the clamps on one day, probably Friday. Also found an epic drill bit in Screwfix that is like a Forstner bit but has more cutting surfaces and angles. It was just over £9, but you may remember part of the problem with the current clamps is that I had no reliable bit that would drill through hardwood so they ended up a bit loose. Through pine the fit of a 32mm pole is pretty tight - needs a good whacking in, so when the slit is cut it should make a nice rock solid lower clamp.

John

[gooseholla]

Today is a mixed day. The spandex turned up for the shroud, which is good. The weather is horrible, which is not good. That meant I couldn't get my bench and router out to do the upper truss clamps. However, it did mean I could do the lower truss clamps.

The spandex is from bstfabrics on ebay. It is 4 way stretch 210gsm. For 3 metres it was just over £20 delivered. Probably work on that middle of next week. Needs  a dry day where I can set the scope up, pin it on, take measurements and then take it away to sew.

The lower truss clamps were made in a couple of hours - how I envisaged them back in January. This time I had two things in my favour. 1. A drill bit that cut through it easily and in one. Before I had a few different drill bit types that either were too long for my drill press and the block, or too short so had to have two or three attempts to make a full hole, or just didn't work at all. 2. Clamps that held the block secure and didn't get in the way of the drill press.

I will put a link to these two items at the end. Really good products for what I wanted to do.

The pole is really snug in the hole now. No wobble or movement when clamped. It only takes a couple of turns of the knob to snug it up and it isn't going anywhere or any play.

These are the clamps and drill bit. The drill bit goes through hardwood easily. Because it has two angled faces on the bit it also ejects the stuff out of the hole pretty efficiently. As you can see, it makes a lot of shavings!

Drill bit: http://www.screwfix.com/p/disston-multi-angle-drill-bit-32mm/33942

Clamps: http://www.amazon.co.uk/Wolfcraft-B3633-Needle-Spring-Clamp/dp/B0001P19OK/ref=pd_sim_60_2?ie=UTF8&refRID=087M3W83B3S92W03WPAR&dpID=31a9J76-krL&dpSrc=sims&preST=_AC_UL160_SR160%2C160

The poles just need sanding and having the slit cut through them. But it was getting too horrible to be outside so I called it a day.

Hopefully tomorrow or Sunday will be dry so I can go and do the UTA clamps.

John

[mapstar]

Nice work John.

Those blocks look well machined now and I'm looking forward to seeing the spandex/lycra shroud.

Also thanks for the links I shall bear them in mind for future reference

Damian

[Rainmaker]

Enjoyed reading your build so far John,  as for the pipe insulation, for a good fit on the 32mm poles, I used the 28mm Superlon insulation.

If you decide to go that way, it needs to be installed with a little care as it is a firm fit.  I taped over the open end of the pole then put a small ball (smaller than 30mm) onto the end and taped again with insulation tape.

That makes getting the 28mm (actually 30mm ID, they are made for a loose fit - I tried the 32mm tube and it was too big for the 32 aluminium tube) on easier.  

Make sure the alu tube is dry and free from any contaminants like glue residue.

I then used a short length of 50mmID heat shrink over the ends to secure them.  You can see the ends here:

[gooseholla]

Today I have done the upper clamp system. Tomorrow just got to drill the holes in the poles and assemble it.

I've made 8 hardwood plugs to go into the tubes so the screw has something to go into.

The top clamp system is a block of 20mm Ash. The part which will hold the tubes permanently is plywood. You'll notice I got it the right way up this time...

I also changed the positions of the upper clamps on the top cage. This was so that when the scope is lower down it is easier for me to use the eyepiece. Not a huge change but just enough to mean I can look down the eyepiece rather than kneel in the grass next to it at a strange angle.

The new lower clamps are done. Real tight fit and only a turn and a bit to make it super tight.

John

[estwing]

I can't tell you how hard it was sowing that stuff...mines the same material..stretch pin in place and sew in situ

[gooseholla]

I can't tell you how hard it was sowing that stuff...mines the same material..stretch pin in place and sew in situ

Wait - the spandex is for the scope? There go my superhero aspirations...

  :grin:

( I know you've all tried it when your material has arrived... )

John

[estwing]

Yup you'll fit in at a Dobfest!

[gooseholla]

Today I finished my upper truss clamps. They're not perfect but the best I could do, so I'm happy.

I made a block that the poles could go into with a hole for drilling so each would be in the same place.

I then inserted a plug in the end of each.

It was then just a case of assembling each.

So there we have it. Four waiting to be tried when it is clear next. Now they are done I can set up the scope to make the spandex shroud.

John

[mapstar]

Nice bit of Jig work there John. I see the wood working talents are coming on quite quickly since you started.

Have you used wood screws to fasten the clamp sections to the poles.  Just to be wary they may wear in time is all I was thinking and may be better with a nut and bolt all the way through but that is something you'll have to trial in the long term. I've seen other owners do it so they will be able to advise better on this.

I am going for a similar clamp system, although each truss will have it's own spindle bolt to clamp and make it more rigid.  Got to do this due to my pole's being smaller diameter as it's a non traditional scope build. I'm taking plenty of pic's along the way.

Damian