Other than grab screws ways to hold pulleys on shafts?
 

There are reasons not to have on pulleys excess ring for grab screw. Many types of locking devices available but all are rather expensive. Could somebody suggest design not too complex to make with manual lathe. For shaft 14mm, width of pulley 19mm. What kind of metal (treatment) to use?

OR just make two holes for grab screws through teeth and give it LockTite as well?

The above posts, and reply, copied to:
"Grub"/set scews for pinion gears, with LocTite ?

matt - any progress on this one - or I missed it out some where else?

irfan, yeah, i've finalised the design and will be making a prototype over the next few weeks. i was going to post some pics but then i discovered the 4:1 thread had been butchered and incorporated into this thread. Theres not much point posting it here as it will just get lost amongst other designs and discussion of grub screws and collars. PM me your email address if you want some details.
Cheers
Matt

Matt, there is nothing special or unique about Chopper's 4:1 drive that made it any better than any other drive in this thread. In fact, it has the poorest angle of wrap on the small pulley and some are going to find that problematic.

Matt, don't worry about your design getting lost in this thread. Keen MM builder & genuine builder-to-be will go through every word in the thread, eventually...

Combining is doing us a favour, we can have every possible design in a single place & IMHO, these design evolve & improve over time. An excellent example is the grinding skid design.
Post your design & lets have fun with it.

I opt for the belt reduction path, love the highest possible gear ratio but also worry about the grip. I have a vivid idea of using an idler pulley running on bearing to increase the wrap angle.

I wonder if I could just push use a plain 6001-zz bearing onto the belt for the job.

I disagree with you Gerald. Choppers was the only one i have seen that used laser-cut and welded steel. It only required a couple of accurate (turned) parts so was within the reach of all mechmate builders, unlike the other designs which need a proper milling machine or working mechmate to build.
and as i said in a previous post, i was addressing the wrap angle in my modifications...

Ken, i agree combining was good as it gave a good overall snapshop of peoples implementations, but i think the original threads should have stayed separate so those that want to contribute on a particular design can do so without wading through other unrelated posts. the combined thread could then have a summary of the design and a link to the full thread. But Gerald has every right to run the forum the way he wishes and i accept that.

I agree with Matt.

Maybe a solution is to centralize all the pulleys in a thread of links to other threads.

Something like this with a 180 deg wrap & same foot print.

Attachment 8348

This is the concept, the holding structure can be any metal.

Correct Ros, and the first step is to centralize them, as was done in this thread. (we had one versus the rest before).

Matt, the laser cut version shown by Leo (castone), before Chopper, did not need welding, and did not not need precision turned parts, which could make it the most accessible. But let's not get into issues of which designs are the most accessible - all of them have plusses and minusses and hence stirring them all into one big pot. If we have clear trends coming out, we can split them up again. Right now there is no clear trend.

Here are some pics again. The belt drives can be built pretty easy . I would recomend having the stand offs made on a lathe but everything else can be done with a hand drill as I made mine with nothing more than a hand drill just to see how well they would work. I have sold about 20 sets of these have not had any bad feed back so far. If anyone needs the drawing or a parts list just PM me.

Here is the parts list.

There is a small error in the parts list Leo...

"4 shafts per motor 1.275” long .500” Dia" Should read

4 Stand-Offs per motor 1.275” long .500” Dia


I just ordered the bearings for mine :)

Thanks for the PL Leo. A couple of small questions though, what keeps the 1/2" shaft from wandering back and forth, just the large gear? An in the pic top right there are two small washers that I do not see on the PL.

The two small washer are what keeps the shaft from wondering around, they work like a thrust washer and ride against the inner race of the bearing one on each side. I supply it in the kit. But you could laser cut your own.

For those small washers, I would use "fiber" or "sealing" washers, the reddish ones you typically find on an oil drain plug on your car/bike/lawnmower/plumbing.

Gerald,

If you don't mind me asking, a good while back you discovered that my pinions and rack were metric module 1.5 vs 1. This limits my minium pinion size. Do you feel that a 4:1 belt drive would be useable if I don't change out my Rack and pinion to module 1 with a 20 tooth pinon to get maximum mechanical advantage with a smaller pinon?

David if your present geared drives are giving backlash problems (and if it is definitely backlash), then a belt drive will give an improvement. But, if you are getting rough cuts for unknown reasons, a 4:1 belt drive could make it worse. It really depends on the problem that you are trying to solve.

Thank you Gerald; That was fast. I don't have any problems with my present setup. My cuts are very smooth. I do a lot of acrylic sometimes up to 40mm. I'm just asking because I'm looking into building a second machine in the not too distant future. Here in Taiwan, there are just so many parts available, making a belt drive wouldn't be difficult at all. Any gearing ratio I can think of can be found here on some shelf somewhere. I can even get any timing gear custom made for very little. However, when I'm ready to build my second Mechmate, do you think there is any benefit of using module 1 rack/pinion vs. what I got now (module 1.5)?

For my second build, I'm thinking of using the Motion King motor with a belt drive. I've been driving your well engineered machine hard for the last three months and there's not even the hint of any problems. Thanks again Gerald!

Ah, now I understand where you want to go . . .

Yes, a module 1 will give you a finer (smoother) drive than module 1.5. So, why doesn't everyone always use module 1 for everything? Some high loads will break the fine teeth (we don't seem to be near that with our CNC routers). Too fine a tooth can clog with contamination (we aren't seeing that either). Therefore, for our routers, we might even be able to go finer than mod 1, but that is not commonly available.

hi guys can i stick in 2 cents been reading and learking for over a year researching drawing planning wishing ran across this tool for reduction drives because that is what i am planning from the get go http://www.sdp-si.com/Cd/default.htm[/URL] this site does the numbers for you you enter the distance center to center on your gears and ratio that you want you can get cad drawings and belt leignths does most of the hard work for you i have played with several models in solidworks and it works very well during my research i read that the more belt contact that you have on your small gear the less wear and tear on the belt correct me if you feel differently :)

Any one who whould like to try them, here are the drawings for the belt drives.

Leo,

You are being very generous with you work.

Leo is the inside mount the same as the standard geared motor mount if some people already have the standard mount?

Well,give a little take a little. The hole is smaller, but a person could turn a spacer and weld it into the original motor mount kind of like chopper did. Then just make the other plate out of flat bar.

Leo, do these work for all 3 axis?

Pablo,

Yes they do. They really work well.

Contact angle/ No. of Teeth
 

I've been reading this thread many times regarding certain 4:1 Reduction designs and the minimum Contact angle or engaged number of teeth on the smaller Timing Belt Pulley. If I read most of it correct, my conclusion is that you "should" have the belt contact a minimum of 6 teeth on the smaller pulley. Correct me if I'm wrong.

However, from what I have seen on many of these designs is to make them as compact as possible using the smallest belt allowable without the two pulleys touching each other. First, are we required to make a compact design or is it a preferred method?

I'm trying to design a 4:1 Reduction Belt Drive using the following parts:
-72 teeth XL pulley
-18 teeth XL pulley
-Belt: 85 Grooves x 17" Pitch Length

Below is a Sketchup drawing of the calculation/layout and the C-C dimensions are 3.44" with an overall aluminum base of 7.9". On the smaller pulley there are 6 teeth contacting and on the larger one 48 teeth contacting. Please let me know if first, how would this design affect the resolution/performance and am I understanding this thread correctly? Thank you.
http://i585.photobucket.com/albums/s...DESIGNTEST.png

_{Gerald or MetalHead: I've tried to downsize the image with little success, please let me know how I can accmplish this. Thank you.}

Leo

I was wanting to have a look at the parts but can not open the DXF files in autocad. It says " Improper linetype name on line 10. Invalid or incomplete DXF input -- drawing discarded."

Anyone else have this issue or a solution.

thanks
Ross

I use http://www.edrawingsviewer.com/pages...XF-Viewer.html to view the DXF, they open without problems

Thanks Pablo - the drawings open fine in the solid works application you have suggested.

Ross

Dave, if I ever got to building belt drives, I would also increase the space between the pulleys a little to get more teeth in contact for the small pulley. Your layout looks good.

Contact angle/ No. of Teeth
 

Based on the above comment you made and seeing many designs here go for the "compact look", I kept wondering why not just incease the C-C dimension and just go with a longer belt. The depth of the Reduction Drive stays the same, just the width gets a little wider, thus allowing more Contact Angle on the smaller pulley.

I'm currently trying to finish off my design (a better mouse-trap:rolleyes:) and will upload any images soon. Maybe this may help others and myself to better understand this whole concept. Thank you.

Dave

That makes 2 of us, personally don't see the need to keep the belt-reduction/gearbox compact... Compactness may looks good (a very subjective thingie) but does it provide any meaningful improvements? I only see degrading of performance i.e. reduced teeth contact.

Another thought, if we play with the distribution of weight & moment of the drive, it may be possible to eliminate the use of the spring by using the motor weight to mesh the pinion on the rack...

Contact Angle/ No. of Teeth
 

Ken,

I was working on my Reduction Drive design when I saw your ealier post (#250) with a sketch showing a longer belt and a 'belt tensioner'. Compared to the overall size of the Mechmate, +-1" on the width of a well designed Reduction Drive is worth it.

As far as eliminating the spring, (Gerald, let me know if I'm correct) I believe it helps eliminate back lash by pulling the pinion gear teeth tight into the rack teeth----elimating any play between the mating teeth. I hope I understand your concept, you're basically saying to use the weight of the motor and momentum to apply pressure from the pionion gear onto the rack--using the Reduction Drive design as a 'see-saw' type device? Let me know if I understood you correct?

Here some early stages of design, the aluminum plates have not been detailed with pivot, mounting points. So far I have the rack, pinion gear, timing belt pulleys, and belt layed out correctly ( I hope).

http://i585.photobucket.com/albums/s...eduction02.pnghttp://i585.photobucket.com/albums/s...eduction01.png

Dave, that is exactly what I have in mind. Even if the stepper motor can't provide enough "counterweight" to replace the spring, the 2 forces will work coherently instead of acting against each other like all the other design we already have here. That (when comes to fine details) is against my life philosophy ;)
Yes, this will increase the size of the gearbox to easily over double, but that also provide maximum possible no. of teeth contact easily 7~9 on the 18teeth pulley. Its a choice one has to make.

Hi Dave,Here's a couple of pictures of my gear boxes that strikingly similar to your design. This design is not original,but is several years old.I am using 4 to 1 reduction, or 72 tooth to 18 tooth. I'm using .5" aluminum outer plates,easy to machine and added benefit as a heat sink to the motors.I chose the heavier 15mm belt over the XL belt not wishing to be bothered by maintenance issues (changing belts),it also provides more
rubber to the sprocket.Weather one debates are there 6 teeth or 8 partially engaged teeth,seems somewhat irrelevant.The question I want to know is, does it work?On this machine it does.How well? My gantry is twice as heavy,there is significantly more drag with the linear guides,my accel rates are set at 30" per second,and I'm using pk2913 motors to drive
these boxes.Here is the mother of all load on these boxes,without issue.
One thing I did discover,the weak link in these boxes were the double
grub screws on the gears,it was a bit much load for the poor screws.
The solution was using loctite primer 7949 followed by loctite 609 on the
shafts--much stronger.

Hi Ron
Thanks for input. Are you using loctite 609 only or in combination with set screws? Are your pulleys made of steel or aluminum? Will loctite make good grip in combination aluminum-steel?

Ken-
True using the motor and gear box as a counterweight would work in theory, but I think in the real world on the size of this type of machine and forces, you could be asking for trouble. I personally don't think doubling, tripling the size of the gear box would ever jusitify a small spring doing the same job. My biggest worry, if the gear box were exposed, is getting bumped by something or someone. That would cause a skip in the rack, thus ruining the job. The spring keeps a constant upward force onto the rack which should by itself counteract any forces caused by the direction and speed of the x and y cars.

Ron-
Thanks for the tip on the locktite, I'll make a note of it for the build. Below is an update design of the Reduction Belt Drive. Just like yours and many others the design is similar except for material, motor placement, gears and details. Also, I'll look into the belt size you mentioned. I'm all for less maintenace in the long if it saves some time and energy.

Below is a second (but not fully completed) design based on my original post. I have not decided the details on how to keep the 1/2" dia. shaft for the larger pulley from moving side to side. A few ideas I've seen here are Lock Collars or stepping down the shaft ends to 3/8" dia. and letting them sit inside 3/8"ID bearings. I'm leading towards stepping the shafts at each end which would mean getting a pinion gear with a 3/8"dia. bore.

I have taken many ideas from many of the designs posted here. None are right or wrong but all have unique approaches to a particular problem or critirier. Thanks all.

http://i585.photobucket.com/albums/s...muba/RDA11.jpg
http://i585.photobucket.com/albums/s...muba/RDA12.jpg
http://i585.photobucket.com/albums/s...muba/RDA13.jpg
http://i585.photobucket.com/albums/s...muba/RDA14.jpg