Tabletop Alt-Az mount concept - incomplete project

Wanna make a scope? Or better still, grind a mirror yourself. Or, you have some good tips in making a really useful accessory? This is the place to show what your hands can do...
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Hardwarezone
Posts: 288
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Tabletop Alt-Az mount concept - incomplete project

Post by Hardwarezone »

Post here to share my experience as recently these few weeks there were forumers looking to mount C90 mak and 5inch newt OTA.
IMO if can bring down the cost of mount , the lower entry barrier will allow more to join this hobby.
Maybe somebody can finish the idea and build something similar.

This wooden tabletop mount was built around 2017 for my 50mm finderscope for quick view when I lazy to setup the tripod and mount.
Inspired when i looked at 4" 6" diskmount images from 2013-2014.
Built it way oversized but did not solve the problem on how to create a saddle for vixen dovetail dimensions. That 75 degree angle cut.
Even when I gave in and bought a ready-made saddle clamp , I don't have solution to mount it as the steel bolt head protrude and interfere.
I anticipate to avoid the shaft bolt head and have bolt-nut attachment for the saddle , the wood disk will need 1-2 more layer and many big holes.
Lazy shortcut alternative is using steel L bracket and make the saddle hold the telescope from under. The L bracket may introduce vibration.


Holding 50mm RACI finderscope without issue.
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I'm stuck here with no solution , haha
Protruding shaft bolt head and need to attach the saddle clamp ontop.
The wooden disk is 140mm diameter. Steel washer 35mm diameter.
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Half threaded shaft , smooth to rotate on the inside but no difference in actual use as the bolt doesn't rotate.
4 screws for finderscope holder.
Pink/purple paint was leftover and I coated it to reduce the wooden pores trapping fungus spores and dust.
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Tension adjusting wing nut , bolt shaft length was really close to estimation , any error and I would have bought too short.
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Parts display.
140mm hdpe plastic disk cut from 5L dishwashing refill container $4 from supermarket
Steel washer 20 cent and more washers cut from hdpe plastic
M10 wing nut , 60 cent
M10 half threaded bolt , stainless steel 201 , $2
Small L bracket , galvanized steel , 8 for $1.40 at Mr DIY , not used in this project
Rounded L bracket , stainless steel , not used in this project
Diagonal support bracket , stainless steel , 20 cent
Philip screws 1 pack
Milk powder can or snack container lid , as sliding surface for bottom azimuth rotation
Vixen dovetail saddle clamp , $24

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Tools needed.
Jigsaw , corded , dongcheng brand , about $70
Screwdriver or drill , corded , makita brand , about $50
Drill bits 2mm to 8mm starter kit , less than $10 , more 2mm drill bits to prepare hole before grease and screw , 10mm drill bit if using M10 bolt as main shaft.
Jigsaw blade , $1.50 to $2 for each pack of 5 , retail price for branded authentic much higher
Jigsaw blade T101ao narrow for curve cut - circle , t224 big wide teeth for straight cut , t118 tiny teeth cut plastic
Plastic cutter , kitchen scissors.


Design mistakes.
I based the estimation on the 50mm finderscope , cut the wood for vertical arm as low as possible to reduce weight.
When I attempted to match it with 5 inch maksutov , there isn't enough bottom clearance.
Rotating the longer azimuth arm for use as vertical altitude arm barely have enough length. No need to redo whole thing , just drill hole.
I used the corner of the wall to get the 90 degree angle , actual result wrong , on hindsight i should have used clamps and proper L brackets when screwing in the main elbow joint.
Hardwarezone
Posts: 288
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Re: Tabletop Alt-Az mount concept - incomplete project

Post by Hardwarezone »

reminder that this saddle clamp is $24 value with free shipping

this is not an advertisement

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Hardwarezone
Posts: 288
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Re: Tabletop Alt-Az mount concept - incomplete project

Post by Hardwarezone »

A little progress on what works and mistakes made.
The wood in 19-20mm thickness plank format not strong enough to withstand drilling so many holes within a tight disk to stack 2 together.
A single block of wood or plastic 35-45mm thick can reduce to only drill 1 center shaft (10-22mm dia) and 4 saddle mounting (6-12mm dia).
I don't think such thick material available easily or cheap.

Not successful but good learning experience. At least bring a closure to this "wood diskmount" idea i had for years.
Better to take the lazy method of using $7 to $15 steel L bracket.
With my center shaft 10mm bolt head hidden under the saddle clamp , i forgot it cannot be grip by my finger and the tightening doesn't work , it just spin.


started with 2 disk and the 22mm auger to hide the center 10mm bolt head and washer
I cut and painted 3 disk in total years ago and these 2 were spares or for azimuth bearing
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from toolbox some 6mm bolts of appropriate length , bought 1 pack online too short because forgot to account fully for saddle clamp thickness and safety after bolt nut
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looks clean and pleasing by itself
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trying to hide the bolt head and washer within a disk
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had to redo base disk after crack when I step 2 feet on it while drilling over a plastic container for sawdust , the bending effect like open durian shell
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this image is absolutely gross , full of holes like lotus
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completed but not usable due to potential crack in wood when heavy load , center shaft bolt head buried and spinning cannot tighten
will disassemble it in the future to recover the saddle clamp
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next time use 2 of these can solve the problem quicker but mount more bulky
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*update with additional test photo
Did a quick few minute test on the moon , this mount isn't safe enough yet for heavy duty serious usage , will disassemble it.
The balance point make the focuser knob block any higher than 40 degrees altitude , if redo need longer vertical arm.
This was what my original concept tried to portray , making a mount for less than $50 sing dollars so beginners especially in developing country can focus more of their budget onto the OTA.

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Hardwarezone
Posts: 288
Joined: Fri May 17, 2013 2:50 am
Favourite scope: maksutov

Re: Tabletop Alt-Az mount concept - incomplete project

Post by Hardwarezone »

Bought a pair of L bracket from Mr DIY store , cost SGD $3.90 for a pair , at JB it cost RM 8.90 (SGD 2.80)
There are many different style L bracket at affordable price , for this design I slowly picked the set out of a dozen with least flaws at the critical welding point.

Initially it seems alright , did a test fit i only need to put a layer of wood to raise the saddle clamp out of the steel edge since I don't want to cut the steel with angle grinder.
M8 hole on the L bracket fits my saddle with leftover spacing for the OTA to not collide.

After I did a paper template to design where to drill the hole for wood and possibly drill into the steel for additional safety factor of more screws ,
I discovered a flaw where gravity pulls in different direction when the L bracket and scope are raised in altitude angle towards the sky.
The 2 L brackets were spaced minimally close together for single m8 bolt to continuous contact from saddle to steel L bracket and for the center rotating shaft m10 bolt 35mm diameter washer to clip onto the 2 steel L bracket.
Because of the minimal spread distance and the lack of rigidity by not being a single solid metal piece, the cantilever load (5.5kg held 12cm away) is similar to the rear claw of a hammer pulling nails out of wood , in this case screws.

I don't want to expand the L brackets wider and cut aluminium plate as the bed for the saddle.
Back to think about more ideas.


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