Meade 16" Light bridge Truss Mod

Hi all,
I recently started a project to modify an existing Meade 16" Lightbridge to a portable version so that it can be transported in a small vehicle or for air cargo, i used design ideas mainly from http://www.reinervogel.net and also from http://www.roelblog.nl/2012/11/bouwv...-truss-dobson/ and would like to thank Reiner Vogel and Roel Weijenberg for sharing their ideas.


Design Constraints and some rules i followed
1) mod must be performed with nondestructive methods of the lightbridge parts.
2) parts from the older design can be used in the new one without altering it
3) reusability to reduce the project cost
4) portability should be achieved so the telescope can be transported for atleast domestic air travel

Workflow :
Day1-4: i used this time to plan out how and what alli must reuse from the older design and hence what new i will have to design from ground up.

Day 4-7: Aquiring raw materials like aluminium shafts , hollow pipes and a slab of alumium

Day7-15: Machining of aluminium mirror cell and truss pole ends and buying plywood sheets ,veneer sheet.

Day16-18: Wood working for mirror box

Day18-25: Assembling the OTA and checking for focus

Day25-30: Making of rocker,ground board and Alt bearings

Expenses: ( INR is indian rupees)
Metal Milling /Lathe work: 6800INR= 106USD
Plywood=18534INR= 289USD
Carpenter=3000INR= 47USD
Aluminium and casting=5150INR= 80USD
CNC wood work=2100INR= 33USD
Hardware, tools and misc: 5084INR= 79USD

total = 634USD


About the mod:

i redesigned the mirror cell partially and used the mirror cell assembly from the lightbridge, i also reused the upper and lower truss holding rings and clamps,secondary cage and az bearings (lazy susan).

i then had to redesign the new truss tubes based on some simple calculations and the rest of the calculations were from Reiner Vogels website, i had to modify some for my requirements.

finally here are the pics :
https://drive.google.com/drive/folde...zQ?usp=sharing
http://imgur.com/a/pvjiU


Problems yet to be solved:
Friction in alt bearings, as i dont have access to ebony star or similar material in small quantity.


comments and advice welcome. :D

Try strips of FRP, the material often used to refinish shower stalls. It's bumpy and works great on large diameter trunnions.
It's available at nearly every local hardware supply place, like Home Depot, OSH, or Loewe's.
The bearings will still remain teflon.
Lots of commercial scopes now use that material.
Ebony Star is long out of production.

[QUOTE=Don Pensack;5996]Try strips of FRP, the material often used to refinish shower stalls. It's bumpy and works great on large diameter trunnions.
Hi Don,
thanks for the info, i shall try this option, and what about teflon, can i use it on the entire surface or just small calculated pieces at 35º from centre at 4 points only ?

Teflon is 4 small pieces, as you note.
The size of the 4 teflon pads calculated to keep pressure on each pad to around 15psi (around 1kg/cm²).

Hi Don,
thank you i shall try doing that, mine comes to 22mm X 41mm and four of these.

That's about 9cm² each, which would translate to a 36kg OTA.
Pads can always be moved apart to increase friction or moved closer to decrease it.

Hi,
yes, the OTA is 36kg , and thanks for the tip, i didnt know about the distance/angle and friction relation

Quote:

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Originally Posted by Don Pensack

That's about 9cm² each, which would translate to a 36kg OTA.
Pads can always be moved apart to increase friction or moved closer to decrease it.

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