Belt drive gear boxes

[bleeth]

This is continued from here:

http://www.talkshopbot.com/forum/sho...d=1#post108544


Sound great Gerry. Maybe we can negotiate some improved pricing too with a combined purchase! I emailed an enquiry for complete kit price and also asked if they had any shop drawings to adapt from.

Torchmate uses one on their lasers which is an open design not too suited for flying woodchips. You can't see much in the picture (attached) but it gives an idea.

I just did a little calc for design purposes based on precision machining of the mounting plate and no "idler arm" using Motiontek parts with a 20 tooth small pulley and 60 tooth large pully to utilize their pre made up 600mm 120 tooth belt the center distance of the two shafts comes out to 196.53mm. This gives a belt length of 600mm which is their larges stock length.
That's like 7" and seems large to me. Mike's list called for a 150 tooth belt and I went with what they had that was closest to that. That's obviously not a critical number and I'm not sure what the issue would be if a smaller belt was used to bring the center distance down. If their 360mm belt were used then the center spread is 76.415. Thats only about 10mm between pulleys and could be too close for comfort but if there are no other physical constraints then the result is about as small as a gear box you could go. For the 400mm belt the spread is 96.455 and that yields 30.6 in between pulleys

[danhamm]

Have you looked at the R&P design at this fella's site, I purchased 12 of his linear bearing slides to play with. good to deal with..

[gerryv]

Hi Dave, Yes, It should be cheaper for two or more sets because of the prep work and setup costs being spread. Maybe some other guys might be interested as well if they come across the thread.

I'll dig around my files on my home computer when I get back as I think I recall saving some images of these things. my gut feeling is that having them on an angled pivot and spring is to allow for self-adjustment for wear of the rack/pinion to eliminate increased backlash over time. Also perhaps to soften the blow, so to speak, in the event of crashing the hard stops.

As my original post stated, I'm also seriously considering a 5' wide new machine instead of going this route. Although Brady's comments were well received and give me more confidence in risking that kind of additional cost, I was surprised that there was only one response from an owner of one of these new units. Maybe everyone is richer than me and buying Alphas these days! Then again, maybe the economy is so worrisome that no one is buying :-(

Gerry

[gerryv]

Hi Dan,
Yes, I took a look following your recent post. Thanks. They could prove to be an option if I decide to widen my current table and gantry to 5'.

I've just finished grinding my rails using an old machinists trick so I'm hoping that I won't need to add new rails at least on the long X axis.

[bleeth]

Edited my last post below for a few calcs.
Dan-No I haven't seen that. It looks pretty interesting and the adaptation to a PRT looks almost no brainer. SB got away from the spring tensioner with the PRS due to the weight and force moments of the gantry. His Nema 34 set is a 2:1 reduction which would mean going back to the well for different motors than Mike suggests or getting different torque and speed results.

Something else I would like to incorporate in the new motor and pulley shaft design would be a keyway instead of just the flat grind. Could mean some post ourchase precision machining.

I'm out of town through Monday now but will see what develops here over the weekend!

[hh_woodworking]

Check here for belt reduction plates http://www.cvsupply.com/servlet/the-MechMate/Categories

[gc3]

Check here for belt reduction plates http://www.cvsupply.com/servlet/the-MechMate/Categories

ooohhhh no not another MM link

[oddcoach]

Hi guys
I'm in for doing this too and i can make the plates and shafts needed.
i can put the key way in and press the bearings in. I will make some calls monday.
already have a design in my head.
John

[Gary Campbell]

Dave, John...
I have a VCPro file that I used to design a double reduction belt box. It fits the PRS bolt pattern and accepts the OEM OM motor. If you want to take a look, send ma an email.

[chunkstyle]

I would be interested in a 3/1 belt drive box as well. I just started drawing up the existing motor mount plates on my PRS to start prototyping a belt box design. I've read and re-read Mikes post over at MM on belt drives and I remember part of the discussion over how many teeth are engaged in the belt (belt wrap is what I think they were calling it) vs. distance between gears. More wrap being better. I'm wondering if that would be a limiting factor in the size of the box. Dunno.