We are having issues with keeping the pinion gears fastened to 1/2" shafts - you should expect lots of problems if you go smaller than 1/2"

Yes, I was just reading the ""Grub"/set screws for pinion gears - fitting and locking them" thread and noting the issues with gears slipping. I'll will have to reavaluate my design for larger pulley shaft. Thank you.

Oleks,
The 609 retaining compound works well with both metals,as I am using aluminum pulleys and steel pinion gear on a steel shaft. You can use loctite 262 red on the screws. 609 is for shaft only.

Dave, timken bearings will solve the shaft question,I use a 5/8 shaft,as Gerald said
"size does matter":D.I also use a gates belt htd 4255m15 at a ctr. to ctr. measurement of 3.625" .Btw the spring is your friend.

Ron, 5/8 shaft? What I mean, what are all the component sizes and specs for your Reduction Belt Drive build? Using the timing belt pulleys all ready spec out for my design, the max bore for the larger 72 teeth timing pulley is 1/2". I did find one source that has the smaller 18 teeth timing pulley available with a 1/2" bore also. I don't think I saw any available in 5/8" bore, especially the pinion 30 teeth rack gear.

I'm not too worried about the c-c measurement, mine currently is at 3.4379" using the above pulleys. I am curious in your design and how a 5/8" shaft was incorporatted into it. I looking into the Timken Bearings, but I want to use my local sources here in town. There a bearing distributor in the industrail park here in town. I think I can get better prices going this route, not to mention they're a ten minute ride away. Thanks again.

Hi Dave, I tend to purchase the parts and then reverse engineer the design. Question does a belt fit a c-c 3.4379" with room for adjustment?What are the bore sizes to all sprockets and pinions. What is the bore on a high quality timken bearing?
In my case the smallest bore for the timkens was 5/8" this was my given value.
The max Bore size given by the gear manufactures is a conservative size using set screws ,where as one size fits all. In order to get the gears on the shaft,I made the star trek decision,to go where no one man has gone before,I over-bored them to 5/8"to fit my timken bearings.In the service industry a cheap part today can be
horrendously expensive in the future.

Dave, the small bore given by pulley/gear suppliers is meant as a "pilot" bore....which means you are expected to increase the bore to suit your application. Very often they are supplied with no hole at all. So, don't assume that the pulley/gear will work on a shaft that fits their pilot bore size.

Gerald,I believe Dave is referring to the manufacture charts,that show the maximum
permissible boring allowed.I too, found that many of the gears ,that I pursued had .5" maximum boring
recommendations.

Ron, when Dave said:

I was fairly sure he was talking pilot bore in that case....they can go much bigger.

For the small pinior gear, some of us have added a ring around the collar to take the grub/set screw. This is mentioned/shown in the plans.

Ron, below is the layout for both the 72 & 18 teeth belt pulleys. The two circles and belt lines represent the actual pitch, not the actual OD of each pulley. As you can see the distance between each pulley is .5729" (sorry, some of the dim lines did not come through in the image).

http://i585.photobucket.com/albums/s...signTest-1.jpg

Ron/Gerald, As far as the max bore: Pulleys are spec from SDP/SI, the 72 teeth one has two bores listed, .375" & .5" with 1.5" hub diameter . The 18 teeth one comes in three bores sizes, .25", .3125", .5" & only available as hubless. The pinion spec from Boston Gear is .5 Bore and 1.22" hub diameter.

If what you're saying worked, then I'll take the Star Trek approach and bore the two belt pulleys to 5/8" dia.. If I go this route I can still go with my original idea of stepping the shaft down on each end. This time a 5/8"OD shaft stepped down to 1/2"OD on each end to serve two purposes. One to be sandwiched between two 1/2"ID bearings and second to accept the 1/2" bored pinion gear.

Even though I have the design "on paper", I'm taking the same concept as you Ron and reverse engineering it once I get the parts in my hand. That why I can tweek the drawing based on actual part dims.

Please let me know guys if everything sounds good so far. Thanks.

Dave, from SDI parts cat. the following pulleys work with that gates specified belt.
a-6a25-018df1508
a-6a25-072nf1512
You may punch these out.

Dave, the 18 tooth pulley is a .5 bore to match the motor. Check out Oriental motor
Pk 299-4.5 with G203v @ 48 volt ps. (large V-8 performance) very stable.

Ron, I'm currently redesigning my Reduction Drive based on your recomendations. I feel a little more comfortable with a wider belt. First what's your opinion on the belt you spec between the vender SPD/SI and Gates manufactured one? I was able to find two distributers for Gates within 8-12 from where I am.

You read my mind, I already had that Oriental motor and Gecko drive spec out for my build. However if I read your last post correctly, the 18 tooth you said is already bored to 1/2"? When I checked SPD/SI it was only available in .25" bore. Which means I have to install a collar around the hub if I bore it to 1/2" in order to increase the hub thickness and allow for a set screws. Again thanks.

Dave,I too feel more comfortable with a wider belt.Either belt is probably fine,Gates is widely known.The 18 tooth needs to be bored to .5" spec.from memory the hub is .69"
that's ok,don't worry about wall thickness.What your going to do is drill and tap @ 90 degrees, through the center of the teeth,2 set screws ---use serrated cupped screws throughout processes. Use 609 &262 ,it will not come off, it will not slip.
check into Antek power supplies, Call Steve at PMDX for a control board advise,he may recommend the classic 122 .

Leo...


On your belt drives what did you use for shafting?

I picked up a piece of drill rod thinking that the pulleys would fit... I received all the pulleys for the drives today and all the pulleys are bored about 2.5 thousands smaller that the drill rod..

Steve, I am using drill rod as well. I found that the pulleys have a lip on them that will need to be sanded off and also you will need a nice tapper on the drill rod for insertion. My pulley sizes are .499-.500 and the drill rod I have is .500.

This is pretty much a press fit application but to loosen it up you could do a few things.

First wrap up one with some masking tap and insert into a chuck. This could be drill press or hand drill. It just needs to be able to do 1/2 inch. Use a very light sandpaper or green pad and polish/sand away some of the surface. Flip around and repeat.

You could ream out the pulleys but it requires a purchase of a ream.

For grins I grabbed a 1/2 bolt that had a 3 inch grip on it. I measure and fitted it to the pulley. The size was .495 and seemed way to loose to me.

If you know a friend with a hydraulic or arbor press this would make life really easy ;)


Edit: If you cant find a friend a pulley puller will work too.

HI Russell...

I stopped off at a bearing shop and picked up a piece of shaft... For 5 bucks it beat out all the other options :)

I do have a reamer and even a press but it was just not worth the risk of damaging one of the pulleys by reaming and I might want to change out the gears someday so pressing them on was a poor third choice...

And as an added bonus they even had one of the small bottles of Loctite 609 I have been searching for :)

Steve, what sizes was the drill rod compared to the pulleys. I would have figured you would have ran into the same problem with any shaft that was .500 round. Drill rod is usually within .001 of its diameter. What size is the new shaft?

Did you also get rid of first 3 and last 3 inches of the rod. I know mine was sheared and not abrasive cut so the rod was deformed from the clamping and shearing operation.

I forgot to mention you could have also stuck the rod in the freezer overnight and maybe heated up the pulley and bearings in the oven. Should have made the operation even easier then pressing in.

I am just curious not trying to bash or anything.

Last but not least question. What did you do for the standoffs. I have been making mine for the last few lunches and still have about 5 more standoffs to tap. I am doing it the old fashion way by hand in the lathe and it is taking me forever. I forgot how much I don't care for hand tapping.

Steve, you need to have a little slop for the 609 to work.
Russell ,A quality tap bit in a cordless drill ,only takes a few seconds in steel or aluminum.You can buy standoffs with pilot holes from Mcmasters.

Oh My.... Hand taping! :eek: Stand by and I will shoot a few pictures to show you how I do it... I have made 4 stand offs in the last 45 minutes!

Here is a post I wrote a few days ago explaining how I tap and some things to make your life easier.. http://www.mechmate.com/forums/showt...3&postcount=49



Here is a picture of the setup I use on my lathe... Drilling the hole takes 10 times longer than runing the tap in! Sorry for the picture quality, All I had was my phone...

Attachment 8849

I chuck up the standoff, cut it to length and then drill the center hole... Then I place a spiral point tap in the drill chuck mounted in my tail piece.. I LIGHTLY tighten that chuck! IF the tap force is too great the tap will spin instead of breaking.. I do not tighten the tail piece so that it will slide along the ways easily...

I then turn on the lathe in forward direction and push the tail piece into the work with my hand... The tap takes a bite and starts threading into the stand-off. I have my hand on the reverse and when the tap is almost complete I reverse the machine and back the tap out...


I wear a face shield for safety. You must have a spiral point tap, really lube up the tap well, go slow and be ready to stop or reverse in an instant... IF you have the tap in the drill chuck correctly the tap will work but also spin if you get into trouble...


Steve

PS Why to these pictures allways make my lathe look like it is a rusting piece of junk?

Thanks for the instruction, Steve. I always enjoy your tips and techniques information. Thanks for taking the time to share it.

Your "junk" lathe looks beautiful to me...especially since I don't have one but would love to.:D

here is what I used for stand offs, cheap, already threaded, come in different sizes, pick em up at most hardware stores, chuck them up in lathe and cut to length. http://www.drillspot.com/products/49...upling_Nut?s=1

Pivot Point
 

I was just wondering if the pivot point is on the same side in all locations. I ask because I am about to countersink all the plates for making Leo's Belt Drive setup and you can make it go either way, but after choosing which way you will have a hard time reversing it.

Did you get your parts from Leo?

Mine were from him and he used a different setup on the gantry plates so that all the belt drives could be made the same...

Thanks Steve, I had thought all of them where built up the same but looking at other builds I had started to notice different directions. Finished countersinking all the plates today and will prep, prime, paint and press in the bearings. I did a mock up of one and all I can say is wow. They are nice!

I posted a few pictures of the ones I built on my build log... http://www.mechmate.com/forums/showt...4&postcount=67

There is also a picture of one mounted to the Z axis. I had to make a spacer to get enough clearance.

Another thing you want to watch out for is the heads of the screws that mount the motor to the plate. Find screws with a very thin head... I like stainless cap screws and bought them for this application but the heads were problematic.. The heads interfere with the large tooth gear and the pivot mountings...

Thanks again, I must have looked at your thread 30 times now and just noticed the geared motor:rolleyes:

I see you are using button caps under the gears that mount the motor. Is this what you mean by the clearance and are they working out for you. The button heads are what I had in mind seeing I have a huge abundance of them.

Yes they are the ones I ended up using... The clearance of the tooth gears is very close and the heads must be thin to miss the belt and gear...

cncrouterparts.com now has a drive sized for nema 34 motors.

Hey guys, chrisd7306 is your friend, he's just finished a design of a gearbox. It's really in the MM design as it uses the current mountings, allows for balanced weight around the pivot and is easy to assemble. While I had some limited input in the design, Chris tried to avoid fabrication processes and if you integrate the profiles into your laser cut list at the start, the job becomes a cinch. Nema 34 XL belt drive with plenty of wrap. Keep am eye out for the shim plate and reversed flange nut (only cos they were my ideas....

So keep an eye out.

I am trying to set up Leo's belt drives in Mach3.. Would anyone, who uses his drives, have the "Steps Per" setting for Mach3?

My heads hurts tonight and I think I would mess up the calculations :(

Figuring things out is easier than you might think. We'll assume that we're using a 30-tooth spur gear that has a pitch diameter of 1.5 inches. We'll assume that we're using a Geckodrive stepper driver that requires 2,000 steps per stepper motor shaft rotation. We'll assume that we're using a belt-drive that has 4:1 reduction, i.e. 18-tooth to 72-tooth.


1.) Find the circumference of the spur gear: Multiply the pitch diameter of the spur gear by PI
1.5 inch X 3.1416 = 4.7124

2.) Find the distance traveled per step: Divide step 1 by the number of steps per stepper motor shaft rotation, which is 2,000 for a Geckodrive
4.7124 / 2000 steps = 0.0023562

3.) Factor in the gear ratio: Divide step 2 by the gear ratio
0.0023562 / 4 = 0.00058905 inches actual travel per step

4.) Compute the steps per inch: Divide 1.0 by step 3 (find the reciprical)
1 / 0.00058905 = 1697.6475 steps per inch

Just change the numbers to match the parts that you use and you'll have a close estimate of the required steps per inch. Be sure that you run some tests to check things out. It's impossible to economically make perfect spur gears, racks, pulleys and belts, so write some code to move an axis 10-inches and then measure the actual distance moved. Divide 10-inches by the actual distance moved, and then multiply step 4 by that number. If necessary, repeat the test several times until the discrepancy is too small to measure. Example:

10 inches commanded / 10.5 inches actual = 0.952380952

1697.6475 X 0.952380952 = 1616.8071 steps per inch

There is a button in mach3 that does this automagically, its on the settings screen, bottom left, called axis calibration.

Look at Mach3 Tutorial videos here, then go to troubleshooting and there, fast-forward up to +/- 5 minutes, you’ll find the full explanation on how to.

Second, we have around here a excel spread sheet that can help you do those math manually, but again, why use the simple way when one can go the complex way…..:rolleyes: :p

Mach tutorial will show you how to do this almost automatically, but for those like me who like to go the complex way, here Gerald excel table !

Amicalement, Robert ;)

I used the calculation to get it CLOSE, then use MACH3 axis calibration to fine tune it. Ran the calibration over a long length and this gave me a good result.

Belt Reduction Build Process
 

After having seen some questions on the forum regarding how to build belt reduction drives, I have decided to document the process I followed. I originally wanted to make mine with aluminium but after having some difficulty with cutters and cutting the aluminium decided to make the first units with Tufnol (Fibre and phenolic composite mainly used for electrical insulation but has good mechanical properties and machines well and easily)

Attachment 10193 Attachment 10194
Step 1: Finalise design (This one based on JR’s original). I am using a 4:1 reduction so needed a bigger area for the driven pulley.

Attachment 10195 Attachment 10196
Step 2: Arrange parts in material to facilitate machining – I am using dowels machined through the material and into the table for registration to enable machining on both sides. (The six holes around the perimeter of the plate) I have also used dowels inserted into the table to enable me to register the plate for the first operations (drilling). The square on the left in the drawing is to give me the required offset from the origin (100 x 100mm). Due to the differences between the XY and Z mounting plates I have made slightly different respective layouts. The above drawings show the machining that will be done on both sides of the plates. For the first plate both sides are the same giving one two complete sets, but for the second plate you need to keep your wits about you as one needs to run the XY file for one side (top area), flip the plate then run the Z file for the second side (top area) then the XY file for the bottom area to cut them out and flip the plate again and run the Z file for the bottom area to cut them out. This seems complicated to explain but will hopefully become clear below.

Attachment 10197
Step 3: Clamp the plate to the table against the registration dowels. The screw down clamps I am using are made from Maple and have different height steps machined on each end to facilitate clamping different thickness plates.

Attachment 10198
Step 4: Drill the registration holes through the material and into the table – when done insert dowels through into the table

Attachment 10199
Step 5: Machine the rebated areas and mounting holes for the first pair of sides. Note the rebated area for the small piece is bigger than required to make sure that the entire surface is clean once cut out from the other side.

Attachment 10200
Step 6: Unclamp and flip the blank over using the through dowels to reposition it to machine the other side. Screw the blank to the table using the mounting holes drilled in the previous step. (note I have removed the dowels in the table along the X axis as the plate was slightly oversize and is actually partly covering those dowel holes – that’s why I am using registration dowels through the plate to make sure the positioning is accurate) Then run the same file again to machine rebates for the second pair. (When doing this step on the next plate be sure to run the file for the Z reduction at this point).

Attachment 10201
Step 7: Machine the bearing rebates, through holes and captive nut slots for the motor in the first pair.

Attachment 10202
Step 8: Cut out the first pair of sides. Flip the blank again and repeat from step 7 for the second pair of sides. (Remember to change files if cutting the Z pair)

Done! – two sets of sides to make belt reduction drives, now just rinse and repeat for the other two.

Attachment 10203
The complete sets of parts cut on the MechMate, the slightly different Z axis drive is on the right.

As an aside I noticed a small anomaly when machining my sets. The bearing rebates on the small pieces were slightly bigger than the bearing rebates of the bigger piece. The bearings go in nice and firmly with moderate pressure in the big pieces but virtually fall into the small pieces. I rechecked the drawings and both are exactly the same size. The only reason I can think of is the resolution of the direct drive system and the relative position of the respective holes on the table. Once I have the reduction drives assembled and fitted I will run these same files again and check the results.

Here is the PDF of the above process:
Attachment 10204

Alan, very nice ......... design and presentation. I like the material, I bet it holds up just as good as alu and is much easier to machine.

Great work! Alan, is there any chance that the bearing rebates in the smaller pieces were cut in a conventional direction and those in the larger were cut in a climb direction?

Fantastic work! Always wonder if those Tufnol are good for structural use.
Maybe lighter cut will help with the hole dimension.