new linear motion driving idea

[max_imum2000]

i am building a new router, it will be mainly for foam cutting.
i was thinking what can i drive it with ?

2 screws in each side ? expensive and complicated setup
2 belt and pully system ? well maybe

i thoght also about chains but i was worred about wear, tensors and so on.
now i have this idea, i dont know if it was done before or not, anyway


how about placing 2 chains (maybe welding them on the machine body side and not making them hang around as usual) side by side with one of them ahead of the other a little bit so that the teath of the sprockets are always in a good contact with the chains

then placing 2 sprockets on the motor shaft and making them roll on the chains as if it was rack and pinon


and repeat that on each side of the router ?

[mxtras]

I am not sure I understand the need for two chains, nor do I understand the need to stagger the chains, but your idea will work.

I have used a single, tensioned chain as a gear rack on an industrial machine in the past.

Scott

[max_imum2000]

hello mxtras
thanks for your reply.
the reason is to minimize the backlash thats all.
maybe i am mistaken on the concept as i thought that the teach will always be in good contact that way.
so how was ur machine performance when u used that idea ?
you used it as a gear rack or you meant a sprocket rack ?
any backlash ?
what was the efficency of motion transfer compared to other systems ?
and what size chain have u used ?
sorry for so many questios , but i am build a table which is about 3meter long x 2 meters wide
one last thing on a table that long can i place the rach on 1 side only ?
thanks

[vger]

Your idea should work as stated. Judging by the size you are talking about I would probably put a chain on each side. If allowed you could put a shaft across the width connecting the two sprokets. If you have your linear track and truck system set up, there might be an alternative to welding the chain down. In some machines I have worked on a system of 2 idler sprokets and one drive sproket was used. The chain was pulled tight with a piece of thredded shaft attched to the end and layed on a support if horizontal. Think left to right here.... chain about 1/3 way around idler in CCW dir, then 2/3 around drive sproket in CW dir, then 1/3 around second idler in CCW dir, and back along original path. Chain makes an "omega symbol" path.

Check out the drive system for a copy machine mirror/lamp carriage. Many are a piece of wire cable (small) wrapped around a drive spool. Very smooth operation, no backlash, and can be very accurate. Could be scaled up to any size. Just a thought.

Steve

[Willbird]

If you could get chain wide enough or sprockets narrow enough you could mount two sprockets tight together and have a provision to adjust them to remove backlash, might be easier than 2 chains ??

Bill

[erase42]

why not use larger size toothed belt instead of chain, its lighter, thinner and quieter and needs no lubrication. you can use the same method as the chain basically. Ive been told by people that have used it, that after an initial stretch, there is no noticable stretch. You could also glue it down to a rail upside down as you were planning to weld your chain. just a thought

[max_imum2000]

i thought about the belt beeing used instead of the chain
but i dont think there are belts that have teeth that long ?
i mean the gears can jump the teath of the belt if there are a strong resistance for any reason, or maybe i am wrong

however since my printers are my main job, i see all new printers and even some plotters that uses wires instead of belts.

just a normal steel wire with no threading.

did anyone tried this before ?

[erase42]

I would worry more about the cable system slipping on a larger scale machine than i would the belt. and if you were to use the belt in the format the other poster mentioned about two idlers and a powered pully, for the belt to skip you would have to skip a good many teeth. also concider the fact that the belts teeth maybe as close as maybe 5 per inch on a larger size belt. even with the smallest chain that ive seen you still only have 2 or 3 at the most.
i know it sounds like i work for the belt company Ive just seen how nice they are on motorcycles, and some machines we have converted from chain drive to belt in cases where its practical.

[millman52]

maybe a picture/sketch worth more than words. Many people on here using either of the designs pictured below to drive plasma, Ox Fuel, Router tables & find both notched belt & sprocket chain in these type(s) of drives.

I think by wrapping the chain or belt around a pulley as opposed to using it rack & pinion style would best eliminate backlash.

I do think what you are suggesting will work if:
(1) Your chain is of high quality & spec.
(2) You get the chains spaced on EXACT centers.
(3) You get your sprockets timed EXACTLY around the drive shaft.
(4) Your Sprockets are of Machined Quality as opposed to stamped or cast.

Just my opinion.

[erase42]

keep in mind that both of the styles have pros and cons. on one hand, while the top style cuts the length of the belt or chain almost in half, the moving aspect of the axis now bears the weight of the motor and mounting hardware ect. the lower style lowers the driven weight a bit due to the remote motor location, the accumulated play in the belt or chain would be greater.

[max_imum2000]

i just rememberd a quote

its true that a picture worth a thousand words
but do u know how megabyte it can take

[vger]

Originally Posted by erase42 I would worry more about the cable system slipping on a larger scale machine than i would the belt.

Should have clarified, the cable is bound to the spool through a slots to pins. A lot like a spool on a giant 200 ton overhead crane I once worked on only the copy machine has a return path counter wound on the spool through the other slot.