Well I've pretty much finished the secondary cage, except for the plate
to hold the finder scope. I had to make a base plate for the focuser
because the focuser board's curve is 236mm dia and the focusers base
is set for a tube of 358mm. But you can see from the photo that I had
to raise the focuser off the focuser board by at least 5mm so the focuser
turn knob cleared the lower ring, I raised it 10mm. So the adaptor plate
performs two purposes Raise and Adapt.
The rocker box is complete with teflon bearings in place. I also used two
Eazy Glide discs 25mm dia on the inside to guide the mirror box in it's travel.
Which had to be countersunk 1.5mm either side, I used a router to do that.
I'm still to attach the base board and still to figure if I want it round or
square. Keeping it square will give a slightly better spread on the three feet.
After that it's pretty much just the mirror cell to complete. I'm going to drill
and tap a thread into each of the three bolts, as marked. In each I'm going
to thread a small flat head brass screw fitted with a locking nut which will
lock against the end of each collinmating bolt to form the pivot for the two
point plate on each point, making a 6 point cell. The image shows the top
side of the cell, I'm going to make three wooden knobs to fit to the bolt
heads (bottom side) and will be spring loaded from the bottom side. I'm
thinking I will probably go with Velcro circle for each point, I'm pretty sure
(although I haven't done the maths yet) that I'm going to be top heavy.
Doing a sling system on such a small mirror although might look a lil more
funky it isn't going to add as much weight with the extra bits to do so. Once
I get the optical system in place I can cut the truss pole to the right length.
Anyways another weekend free of kids to experiment.
regards,CS
It looks great Rob. It's nice to see the telescope assembled after working on it for a while, you can see the work that went into it.
To make your mirror box look even better you could always change the knobs on the truss connectors from the wooden ones you have to some nice shiny brass one that you can get from your hardware store.
yeah! had been thinking of doing something with them. As you see them
there, they haven't been finished off. I'm definitely looking to change the
SC connector knobs. The wing nuts are temporary, Bunning has the Black
plastic tri-nut's that will fit the thread for those. But braas down the
bottom would look good, plus add a little bit of weight. All that's left to do
is finish the mirror cell now, need to get hold of a tap & dia set. The base
board just needs to be stained and sprayed. I stripped the varnish off the
old board and cut it down to size.
This weekend has been spent mostly building a case for my 20x80's. Using
a box I built to put the first edition SC in. The New SC has slightly wider
rings and no longer fit in the case. She's going to be a solid bino case 12mm
ply lol. Well it was intended to be a step up for the boys when needed.
Anyways looking at possibly star testing in the next week.
Did the formica work out rob ?.. i 'll try and find this online store i came across .. they really had all sorts of knobs in differant threads .. worth a look
The formica worked a treat, thanks for that. All thats needed to do now
is finish the mirror cell. And with that it's just a thread and tap job, I just
have to get some little bolts to suit. Hopefully I'll grab something in town
later. I brought a little tap and dia set the other day, but it's metric.
Anyone know what the general rule of thumb is when tapping a thread,
what size hole to drill for a particular size thread???
I know that in Timber and Hardware all you have to do is ask for the tap and they will give you a suitable drill bit. Anyway when you buy the tap the drill size is mentioned on the packet.
I know that in Timber and Hardware all you have to do is ask for the tap and they will give you a suitable drill bit. Anyway when you buy the tap the drill size is mentioned on the packet.
Ed,
I went cheap and got a set from Crazy Clarke's 40pcs set for $15.00
They're so cheap you dont get instructions except where it mentions
sizes it states....
Here you are Rob, a scan fom my handy fitters reference booklet
I would advise some cutting oil or paste, without it you can break the expensive ones too.
Just noticed you got fine ones too.
Cheers
Bill
Last edited by Glenhuon; 23-11-2007 at 11:40 PM.
Reason: More info
Well I had a go last night, I took Ed's advice and went and brought
a better tapping dia made of apparently "high quality carbon/chrome steal"
by P&N. It shattered on the second hole, before it had even hit the business
part of the tool. I didn't use a cutting paste, as the packet only states "For
best results use a cutting lubricant" it didn't mention any danger of the tool
shattering if a lubricant is not used. I remember years ago putting threads
into plate steal, So I used the same approach as I did then ie: cut a 1/4
turn, wind back a couple of turns then cut another 1/4 turn or there about
it was more like 1/8 turn cuts.
Anyways I'm going to return it from where I brought it and get it replaced.
Even my machanic mate who was with me when it shattered said "And they
call this carbon steal?" the thing was crumbling trying to get the piece still
stuck in the job with a pair of vicegripps.
On another note, I finished another little project of building a case for
my 20x80's which has come out pretty good I reckon. Made from the
case I originally had built for the SC for the 8" truss dob but the second
version SC was made a little larger than the first and no longer fit.
Update on the broken tap, Mitre 10 are going to replace it. But they have
to order another, which will be here next week.... things a move a slowly
out in the bush , seems a lot of drama just to tap 3 threads.
the bummer thing about it is I wanted to complete it this weekend while I
had no kids about. Oh well at least I can make a decent start on my bino
mount.
Its good that they are going to replace it Rob. Especially with small taps you have to be careful not to put any sideways pressure on them as you cut the threads. Tapping close to an arc weld can be a problem too, as if it has cooled a bit too quickly it can form what we used to call "diamonds" in the metal, seen even hi speed steel taps have problems with those.
Its good that they are going to replace it Rob. Especially with small taps you have to be careful not to put any sideways pressure on them as you cut the threads. Tapping close to an arc weld can be a problem too, as if it has cooled a bit too quickly it can form what we used to call "diamonds" in the metal, seen even hi speed steel taps have problems with those.
Bill
(Who has broken 3/4" taps in his time )
Thanks for the tips Bill, I'll be taking it reeeeeal! easy with the next tap.
On another note, I made good head way on my bino mount today. Still
a long way to go but at least is started. With the main arm pretty much
together.
Well I finally got the mirror cell sorted out last night. Just need to make
some knobs for the colinmating bolts. and whack some velcro on the cell
and mirror and throw it in the mirror box. I still think the whole setup will
be top heavy and will have to make up some sort of counter weight. But
I should be able to start testing it over the next couple of days.
Installed the mirror cell and tailgate this afternoon. Also installed the focuser
and secondary mirror in the SC, which I'm pretty happy about. The two images
below show the alignment of the first edition SC when I had first installed the
focuser (first pic). And the second edition SC (second pic). The second
editon came out bang on, if only slightly but not enough to worry about, off.
I did the alignment with a Cheshire <-typo eye piece and a card marked up
and stuck on the oppisite side of the SC.
Just need to throw the mirror in and take it outside and see if I can get a
star to focus. My estimate is my truss poles are about 25-32mm too long.
I do have a top heavy problem which I kind of figured would present itself.
Here'sanother project I've been working on, my parralellogram mount for my
20x80's. At this stage it is very much incomplete and I have yet to shape,
sand, stain...etc...etc... what I have here. I just put it together to make
sure it works machanically. Also I intending to add another arm with counter
weight on the end of the main arm, like a back-hoe. the main arm has a
900mm reach, with the second arm I'm going to for an extra 400-600mm
on top. This should enable you position the bino's anywhere around your
head without having to move your seat. Also it will reach over my favourite
bino chair, our trampoline . Well that's the aim.
except where it mentions
. Well that's the aim. 
