The 14" build is finally underway

[Dave_D]

i think i made a bit of a gaff with the position of the 3 handled bolts... the rearmost one could really do with being 2 or 3 inches higher to give a bit more stablility... tis not a problem though.

[Davey-T]

Looking good Dave, you can get Blum kitchen unit hinges designed to throw out further and a bit stronger as fitted in 35mm holes.

Dave

[Dave_D]

been pondering the bearings... i've allowed 10mm between the rocker arms and the base to fit something like a formica edging and teflon blocks to the runners

i've got these 2 great big lumps of teflon from where i used to work... need to find someone with a band saw to cut 2 disks off about 10-12 mm thick which hopefully, i can machine down to the required thickness with a fly cutting bit on my CNC. never tried machining plastics though.

[Dave_D]

2 minutes ago, Davey-T said:

Looking good Dave, you can get Blum kitchen unit hinges designed to throw out further and a bit stronger as fitted in 35mm holes.

Dave

yeah i was considering those, but there's practically no weight on the hinges as they only need to hold the rear panel

[Dave_D]

i really hate the camera in my tablet ? 

added carrying handles, flip out rear panel (not shown as it was being painted) for mirror access and 50mm x 3.5mm steel brackets fitted through the mirror box to mount the truss pole connections, bolted with 2 M6 bolts each bracket and big enough to spread the load across the box.

need to dremel 10mm off the 6 handled bolts holding the runners on as the middle bolts currently interfere with the mirror cell 

just need to make the mirror retention clips and waiting for the smooth edging strips to arrive for the runners

having trouble finding suitable springs for the cell though... anyone got any suggestions? 

 

Edited December 6, 2018 by Dave_D

[hughgilhespie]

Hi Dave,

Try https://www.leespring.com/uk_index.asp

Good range and order online. I have used them quite a bit.

Regards, Hugh

[Dave_D]

todays progress... the base is all cut and ready to paint. just deciding on a 16 inch lazy susan...

anyone had experience of these? 

https://www.amazon.co.uk/Unilocks-Aluminum-Turntable-Revolving-turntable/dp/B00BHSPAJU/ref=sr_1_50?rps=1&ie=UTF8&qid=1544281198&sr=8-50&keywords=lazy+susan&refinements=p_76%3A419158031

or recommend a better one?

and just as a shameless bit of plugging, if anyone is planning to get a CNC router, i can honestly say this Ooznest Workbee is fantastic.

[sloz1664]

Dave, I know it's off topic, but what options do you recommend regards the Ooznest Workbee.

Steve

[Dave_D]

1 hour ago, sloz1664 said:

Dave, I know it's off topic, but what options do you recommend regards the Ooznest Workbee.

Steve

i got the 1000mm x 750mm screw driven because it fits perfectly into my balcony alcove. i *would* have gone for the 1500mm x 1500mm if i had space. the screw driven is definitely better than the belt version. also, i went for a proper spindle as the dewalt and makita trim routers ooznest supplies, although quite functional, are hella loud in use.

[Dave_D]

hmmm... not sure if this bearing is big enough...

[Dave_D]

this bearing is going to work really well... supposed to have a load capacity of 200kg. bit of overkill but y'know... kids had fun spinning me round on it

that's my girl singing to youtube btw... 

 

 

[Dave_D]

i always thought that the truss fixings would be the stumbling block of this build... oh so not true  

£4.50 a piece as opposed to who-knows-what-with-standard-astro-500%-markup truss connectors.

a wee bit of fettling on these aluminium go-pro butterfly diving connectors and all is good in the world. can't use the original handles to tighten them up but hey, that's what 3D printers are for    just need to design and print conical handles now...

Edited December 28, 2018 by Dave_D

[estwing]

Cost cutting ...I like!

[Dave_D]

So after what seems like an eternity wrestling my demons (don't ask), i've got my finger out again. top ring is coming along, the first part of the focuser mount is 3D printed with heat inserted threaded inserts to clamp the top section (which is currently still in openscad being finalised) to hold it all in place, just need to make the spider now. Waiting for the 25mm dia plastic knobs to arrive so i can finish the truss poles.

[Dave_D]

works far better than i thought... seems very stable even without the top section bolted to the top ring

[Dragon_Astro]

Looking good so far, hoping the the progress continues

Youve gone for the same type of top ring as I did for my 12” truss dob.

[PlanetGazer]

Great work! can't wait to see the final piece!

[Dave_D]

finally starting to look like a scope

just 4 more truss pole ends to make then i can shorten the poles to the right length and do the spider and finish the collimation side of the mirror cell 

[CraigT82]

Wowsers what's the FL on that! Looks like it's going to be seriously neat and ultralight style

[Dave_D]

3 minutes ago, CraigT82 said:

Wowsers what's the FL on that! Looks like it's going to be seriously neat and ultralight style

the primary is 14.5inch F5.6 (80 inches give or take a bit)  but i bought 2000mm poles. there'll be somewhere round 400mm coming off them once i get the primary cell completely finished so i know exactly where the secondary will need to be to complete the measurements.

it's actually a lot heavier than it looks as it's made from 18mm exterior waterproof MDF, but y'know, that's what cars are made for

[Dave_D]

and yeah, there's only 6 truss poles there but i wanted to play

[saac]

Dave that is looking really good, well done.  Have you decided how you are going to size the truss tube  - by calculation or practical method ? I took a rather Heath Robinson approach to mine and focused on the moon by sliding the upper OTA up and down the tube until I found the sweet spot  (focuser at mid travel) . Looking back it was less than elegant; he jig I used was heavier than the telescope !  Good luck with the rest of the build you will be itching to get first light. 

Jim 

[Dave_D]

20 hours ago, saac said:

Dave that is looking really good, well done.  Have you decided how you are going to size the truss tube  - by calculation or practical method ? I took a rather Heath Robinson approach to mine and focused on the moon by sliding the upper OTA up and down the tube until I found the sweet spot  (focuser at mid travel) . Looking back it was less than elegant; he jig I used was heavier than the telescope !  Good luck with the rest of the build you will be itching to get first light. 

Jim 

i've got a full 3D model to work from. only things i don't know yet is the exact distance to the surface of the primary  until i find decent springs for the primary cell and the secondary holder size. i kind of guestimated them in the model but until they're physical objects, well... y'know