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  #271  
Old Wed 03 March 2010, 15:16
PEU
Just call me: Pablo
 
Buenos Aires
Argentina
I use http://www.edrawingsviewer.com/pages...XF-Viewer.html to view the DXF, they open without problems
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  #272  
Old Wed 03 March 2010, 16:17
Surfcnc
Just call me: Ross #74
 
Queensland
Australia
Thanks Pablo - the drawings open fine in the solid works application you have suggested.

Ross
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  #273  
Old Wed 03 March 2010, 20:19
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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.
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  #274  
Old Wed 03 March 2010, 20:40
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
Contact angle/ No. of Teeth

Quote:
Originally Posted by Gerald D View Post
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.
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) and will upload any images soon. Maybe this may help others and myself to better understand this whole concept. Thank you.

Dave
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  #275  
Old Wed 03 March 2010, 20:59
KenC
Just call me: Ken
 
Klang
Malaysia
Quote:
Originally Posted by Temuba View Post
............I kept wondering why not just increase 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......

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...
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  #276  
Old Wed 03 March 2010, 21:41
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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).

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  #277  
Old Wed 03 March 2010, 22:42
KenC
Just call me: Ken
 
Klang
Malaysia
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.
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  #278  
Old Thu 04 March 2010, 12:26
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
Attached Images
File Type: jpg cnc build job 011 (Small) (2).jpg (32.3 KB, 1953 views)
File Type: jpg cnc build job 012 (Small).jpg (30.0 KB, 1952 views)
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  #279  
Old Fri 05 March 2010, 00:34
Oleks
Just call me: Oleks
 
Poltava
Ukraine
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?
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  #280  
Old Fri 05 March 2010, 12:07
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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.




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  #281  
Old Fri 05 March 2010, 12:29
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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"
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  #282  
Old Fri 05 March 2010, 12:46
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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.
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  #283  
Old Fri 05 March 2010, 13:17
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
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  #284  
Old Fri 05 March 2010, 13:58
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
Dave, timken bearings will solve the shaft question,I use a 5/8 shaft,as Gerald said
"size does matter".I also use a gates belt htd 4255m15 at a ctr. to ctr. measurement of 3.625" .Btw the spring is your friend.
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  #285  
Old Fri 05 March 2010, 17:30
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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.
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  #286  
Old Fri 05 March 2010, 20:13
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
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  #287  
Old Fri 05 March 2010, 23:24
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
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.
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  #288  
Old Sat 06 March 2010, 07:38
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
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  #289  
Old Sat 06 March 2010, 09:06
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Ron, when Dave said:

Quote:
Originally Posted by Temuba View Post
. . . the max bore for the larger 72 teeth timing pulley is 1/2". . . .
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.
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  #290  
Old Sat 06 March 2010, 11:36
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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).



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.
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  #291  
Old Sat 06 March 2010, 12:47
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.

Last edited by cab. guy; Sat 06 March 2010 at 12:50..
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  #292  
Old Sun 07 March 2010, 09:15
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
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  #293  
Old Sun 07 March 2010, 20:03
Temuba
Just call me: Dave
 
Vineland,NJ
United States of America
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.
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  #294  
Old Sun 07 March 2010, 21:08
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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 .
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  #295  
Old Wed 10 March 2010, 21:33
swatkins
Just call me: Steve
 
Houston
United States of America
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..
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  #296  
Old Thu 11 March 2010, 18:57
Regnar
Just call me: Russell #69
 
Mobile, Alabama
United States of America
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.

Last edited by Regnar; Thu 11 March 2010 at 18:59..
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  #297  
Old Thu 11 March 2010, 19:22
swatkins
Just call me: Steve
 
Houston
United States of America
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
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  #298  
Old Thu 11 March 2010, 19:48
Regnar
Just call me: Russell #69
 
Mobile, Alabama
United States of America
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.

Last edited by Regnar; Thu 11 March 2010 at 19:52..
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  #299  
Old Thu 11 March 2010, 20:11
cab. guy
Just call me: Ron
 
Boise,Id.
United States of America
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.
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  #300  
Old Thu 11 March 2010, 21:14
swatkins
Just call me: Steve
 
Houston
United States of America
Quote:
Originally Posted by Regnar View Post
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.


Oh My.... Hand taping! 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!
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