crayford homebrew focuser

[chazbear]

hi all

on going project at moment is a 6inch newt i am looking to make my own focuser if possible a crayford type... been serching for plans to build one but not having much success can anybody help...i have full access to a machine shop so all i need is dimensions and a drawing all ideas gratefully accepted.....failing that suppose it will be a rack and pinion job...but i am keen to make my own

regards chazbear

[marcopolo]

I made one a number of years back before my break in Astronomy. It's so simple you could just copy it without even needing dimensions. it uses teflon sliders instead of bearings. Not sure if I was re-inventing something that had already been tried but i'd never seen it done before and it's ultra silky and smooth:

Homemade Crayford Focuser

Surprised my old webpages are still up. I told yahoo to take them down about 2 years ago!!

FYI ,the focuser is sitting on a shelf gathering dust. as i plan to make a 2in version for my larger scopes. (the one pictured is 1 1/4in).

I think I ran off some CAD for it so may have dimensions to convert to PDF. I'll take a look.

Marco.

p.s. the design shouldn't work well as teflon has an initial stiction to get over and it should pop the drawube up which wouldn't be very good for trying to fine focus!!! However after much head scratching I realised why it wasn't popping into action and flowed smoothly when truning the focusing knobs: the pinion acts essentially like a clutch enguaging the drawtube only at the point where there is just enough force to overcome any stiction. If it was fully coupled wiht the full force of the pinion it would have been a non starter and the design wouldn't have worked. This is a complete accident as initially I neitehr anticipated the problem or the accidental ascpect of the design that causes the 'design flaw' to not be a problem ie the 'clutch lke action' o the heatshrink tubing over the aluminium pinion!!!

[chazbear]

hay marco

i did see your page whilst trawling thru the web that is exactly what i had in mind...but if you could get the dimensions ie height of focuser from base plate to top(thickness of plate used) and length of the actual tube that would be fantastic

many thanks chazbear

[chazbear]

me again

it helps if you read your page:confused:... most of sizes are there all i need is the length of the focuser tube and over all height including base plate

thanks again chazbear

[marcopolo]

No problem, give me a few days and i'll convert the CAD to PDF and post it up. I did do a statics calc for the loads on the pinions etc...and the spring force needed. I'll see if I can dig that out too as it's converted to an xls calc sheet.

[marcopolo]

Ready to send you CAD (in PDF) and XLS calc for dimensions (you input maxinmum eyepiece weight, required travel etc...)

[chazbear]

hay marco

thats really great...ive given email hope you got message

many thanks regards chazbear:hello2:

[chazbear]

marco

had a squint at your drawings...exactly what i need.... the dogs b++++++s thanks again

regards chazbear:icon_salut: