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  #121  
Old Tue 21 July 2009, 11:12
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
It has 5 teeth in full contact (110 degrees of wrap)
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  #122  
Old Tue 21 July 2009, 13:11
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
sorry didn't mean to mislead I didnt do any calc's to figure it out just by educated guess
//chopper
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  #123  
Old Wed 22 July 2009, 02:54
javeria
Just call me: Irfan #33
 
Bangalore
India
is not 5 teeth is contact less than the recommended value?, it will work no doubt , but..
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  #124  
Old Wed 22 July 2009, 03:41
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
5 or 6 teeth in contact seems to be very common for these typical belt-drive transmissions. You could always reduce the big pulley diameter and increase the center distances, but the number of teeth gained is not big.

However, I think we are already breaking the design rules in terms of torque vs belt size and enclosing for wood chips, so another rule or two broken might fit in with our "design philosophy"?
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  #125  
Old Wed 22 July 2009, 04:41
javeria
Just call me: Irfan #33
 
Bangalore
India
G- what i was considering was a small idler which will correct this (might require a bit larger belt - but it would then be much closer to the design specs of 6+ tooth engagement.

adding a idler should not be thought to be another complex thing - but a necessity in this sort of small center distance situation.

RGDS
IRfan
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  #126  
Old Wed 22 July 2009, 10:55
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
I do not know what the worry is about with how many teeth contact the pulley,
I do understand the more the better, but if you are worried about jumping a cog or ripping the teeth off the belt it wont happen, the machine will drag me across the table and not skip a beat, I think over engineering is also a problem,
//chopper
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  #127  
Old Wed 22 July 2009, 11:25
javeria
Just call me: Irfan #33
 
Bangalore
India
Per the link below

http://www.sdp-si.com/D265/HTML/D265T056.html

the minimum tooth engagement is required in the case of loaded pulleys and in our case I am assuming it is not, so I think we are still ok
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  #128  
Old Tue 28 July 2009, 20:29
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
for all that are interested I will be placing a post in the marketing section with pricing etc..
thank you //chopper
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  #129  
Old Sat 01 August 2009, 18:08
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
I am not trying to make a sale, I want you all to know that the belt drives are better, and as mentioned in above posts, no they wont slip, or jump cogs, the motors will loose steps before that happens, unless you are using really large motors, anyway here are some pics of the difference between the oriental 7.2 geared reductions and the 4 to 1 belt drives:

The top thinner plate is the belt drives the lower the 7.2's

These were cut with the same router, same type of bit, both bits were new when the cuts were made, no lube.


I am also considering drawing these up in a dxf file so they could be included with the laser cut parts if Gerald will allow this, the bearing cups and the shafts would need to be machined, I am currently working on a way to make it easier build these, but quite frankly I don't think it can get much easier. I could supply the bearing cups and the shafts or you can get them made locally.

//chopper

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  #130  
Old Sat 01 August 2009, 18:14
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
you can see that the top has no chatter marks in them this is because the backlash has been removed, the aluminum looks kinda rough but the pics are really close up so you could see the difference also I checked the run out on the router and it is at 6thousands of an inch, just think of how smooth the cut could be with a spindle with 2-ten thousands run out to 1 thousands run out instead of a router....
//chopper
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  #131  
Old Sat 01 August 2009, 19:15
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Chopper,
Those cuts look great. Do you have any comparison cuts in 3/4 MDF for example? Im sure Gerald would not mind you posting the DXFs for the reducers.
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  #132  
Old Sat 01 August 2009, 19:37
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
no I do not have a comparison for the mdf, I rarely cut it, I mostly cut aluminum and plastic,
//chopper
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  #133  
Old Tue 04 August 2009, 16:44
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
I have had little time to do much lately but I took some time today to draw up how the transmissions are made, so you can do these yourself, and if you do not have all the equipment need to do the work A local machine shop will easily be able to do this, all my measurements are in the inch system those of you using metric parts will need to convert the sizes to fit your bearings and shafts you are using
most of these measurements are not critical there is room for deviation,
the holes in this plate were punched with an iron worker, you could use a drill press, a drill and a vise etc... the center hole for the motor shaft doesn't need to be exact as long as the shaft clears the mounting plate and moves freely for adjusting the same goes for the holes where the motor bolts to the mounting plate, you may want to elongate them to fit what you are doing or if you need more adjustment, if you use an iron worker you will need to check to make sure that the plates are flat when you are done, the iron worker can curl a plate when punching holes in them.. the material I used was .250 thick
//chopper
Attached Images
File Type: jpg motor mounting plate.jpg (37.8 KB, 2687 views)
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  #134  
Old Tue 04 August 2009, 17:04
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
the next part is the motor adjusting plate, this could be omitted if you desire,
I thought it supported the motor better, you could use washers under the mounting bolts, as an example ( use this information at your own risk ) the line to the left side of the drawing is where it would be broke (bent) at 90 degrees to the base this is where the adjusting screw pushes the motor to adjust.
the holes that the mounting screws go through need to be large enough to allow clearance from the mounting bolts I drilled mine .200.
the center hole is the key to this part, it should fit close to the shoulder on the motor but not bind on it, I cut mine out with a hole saw and then used a boring bar to size them correctly, but with the right size hole saw and a file you could get close enough, or a plasma cutter with a hole jig etc.. it doesn't need to be exact, it just needs to move the motor when you adjust the screw.
I used a .0625 1/16 of an inch plate to make these, when you brake (bend)
the part put the end with the large hole into the brake or vise if that is what you are using otherwise the big hole will distort, I don't know if the hole sizes will differ from motor to motor or if this is a nema 34 standard you will need to check your motors before you make the large hole in the plate to make sure that it is sized correctly
//chopper
Attached Images
File Type: jpg motor adj. plate.jpg (32.2 KB, 2681 views)
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  #135  
Old Tue 04 August 2009, 17:10
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
the next part is the drive shaft
these are quite simple to make I used .5 cold rolled round stock, cut them to length and milled the slots in them at 90 degrees to each other,
you could put the flats in with a grinder, they do not need to be to deep just low enough so the set screw gets a good bite... this also makes it easier to remove the parts since the shaft will not get marred from the set screw making it difficult to slide parts on and off the shaft, but if you desire you could also omit the flats.
//chopper
Attached Images
File Type: jpg shaft.jpg (14.5 KB, 2656 views)
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  #136  
Old Tue 04 August 2009, 17:45
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
next is the bearing boss,
this one is the hardest to make but not difficult if you have a lathe, or mill (drill press)
I used a piece of pipe to make mine,
what is critical here is the 1.125 bore that goes into the part you need this loose enough to put the bearing in but tight enough so the bearing doesn't spin
you also want to leave a little bit of the bearing sticking out aprox. 10 thousands of an inch ( this does not need to be exact) the reason for this is when you assemble the drives you want the big pulley to rub against the bearing not the bearing boss since the bearing is spinning on the shaft the same as the pulley it will not wear the pulley by rubbing etc. when you look at the drawing you will see two different side views because there are two different bosses ( this is an improvement from mine) the boss that is thicker will be welded to the new motor plates to give more clearance for the large pulley and the bolts that hold the motors on you will understand this when you assemble the parts, the smaller ones will work but since you are making them why not make it better..
once these are machined I checked the bearings fit, in the boss you want them to go in with finger pressure or a light tap with a hammer but you do not want them to tight or it will distort the small bearing making it hard to turn, also if the bearing is to loose all is not lost ( unless it is really loose)
you can clamp a small rod or similar device into your vise slide the boss onto the rod and heat the boss up red hot and quickly grab it with a pliers and put it into a cold bucket of water this will shrink it slightly and tighten up the fit to your bearing you can repeat the process till it fits, but you will only gain a few thousands doing this, ( this is the reason I chose to make these out of steel )
also when you weld these to the plates you need to weld them evenly around the boss to keep it from distorting the boss, also you want small welds not much more than spot welds I welded mine in three spots around the boss.
after you are done welding them check the fit of the bearing if it seams tight from the welding use a die grinder and ease a little off the boss where the welds are till the bearing fits.
when you weld the boss to the motor plates make sure you have them on the correct side of the plate, on mine I put the transmissions together so they would use the weight of the motor to push the pinion gear into the rack, on the z drive the plate goes to the outside of the mechmate plate for clearance issues on the z assembly also when you weld these to the plate make sure that you clamp them down tight so they do not move
while welding, also you want to weld them quickly when welding if you do not do them properly the boss will lift up on the side that isn't welded as the weld cools.
//chopper
Attached Images
File Type: jpg bearing boss.jpg (28.5 KB, 2694 views)
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  #137  
Old Tue 04 August 2009, 18:03
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
next part is the stand offs they are made from band iron I use .250 thick
1.125 wide and cut them to length, mine were 2 inches log but if you are using the bigger bosses you will need to be 2.250 long there are two of these on the Y motor and both X motors, on the Z you will need to brake the band iron to go around the big pulley for clearance if you look back at the pics you will see what I mean, I attached it to the 45 degree angle on one side of the motor plate, you need to put these in a location that will allow you to put the big pulley in place and remove it if say a belt breaks, look at the pics for reference
also when assembling these I put a piece of card board between the pulley and one of the bearings for clearance ( milk carton box) or a thin washer will work. I would rather have to much of a gap here than not enough, it is easier to squeeze the plates than push them apart.
also be careful when welding the stand offs in if you get them to hot you could warp them.. and this will require more work to get them straight...
when you Finnish welding and let the part cool check the clearance on the pulley and the bearings
if this gets to tight you may need to push them apart with a porto-power duck bill, to get the clearance back that is needed for the pulley to spin freely
no pics for these reference back to the pics of the drives if you have questions please ask
//chopper
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  #138  
Old Tue 04 August 2009, 18:06
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
if you want to know I am running the kelling
450 ozin motors # KL34H260-60-4A
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  #139  
Old Tue 04 August 2009, 18:25
chopper
Just call me: chopper
 
Big Lake Minnesota
United States of America
also if someone wants to add these to the laser parts kit it would make it a lot easier to build these things , then I that would be needed would be the shafts,stand offs and the bearing bosses
//chopper
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  #140  
Old Tue 04 August 2009, 23:24
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks for all that info Chopper.
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  #141  
Old Thu 27 August 2009, 17:44
Castone
Just call me: Leo #41
 
Soddy Daisy , Tn
United States of America
Low cost belt drive

I have still have been working on a low cost belt drive and think that I am about there. I have used two press fit bearings with the flanges to the inside,I also added a thrust bushing on each side of the pulley so there would not be any play. The bushings are .500" ID by .630" OD so they will ride on the inner race of the bearings. Pictures do not show the standoffs. These bearings were press fit into the laser cut holes with no machining. I inspected the parts on our CMM to check the roundness of the cut and before and after pressing the bearings in. Bearing flex was about 3 tenths of a thousands.The laser cut plates ran out about one and a half thou true position.But by using a thrust bushing on each side and turning the flanges both to the inside the press fit can be a very light fit. I have counter sunk all the bolts on the working side of the motor mounts so that it is flush. The stand offs on that side could be tack welded after assembly. Thanks goes out to JR and all the others who have help by ofering there input. Total in parts so far around $180.00 for all 4 motors not including laser parts and standoffs. I will be glad to share the plans I have to anyone building a MechMate. I will post some updates after some more testing.
Attached Images
File Type: jpg Tranny pics 005.jpg (58.1 KB, 2334 views)
File Type: jpg Tranny pics 008.jpg (54.6 KB, 2337 views)
File Type: jpg Tranny pics 010.jpg (67.1 KB, 2348 views)
File Type: jpg Tranny pics 012.jpg (60.9 KB, 2332 views)
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  #142  
Old Thu 27 August 2009, 22:27
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Leo,
Looks very interesting.
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  #143  
Old Thu 27 August 2009, 23:40
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Wow, you have amazing tolerances on your laser cutting!

I don't think that all laser companies have the same tolerances (and kerf width) so any published plans would have to be treated with caution. However, there is nothing wrong with cutting slightly undersize and then licking the holes with a file or pencil grinder.....a dash of LocTite will always be welcome.

On countersinking lasered screw holes:
Here at my factory, I make the lasered hole much bigger so that the countersink cutter has less work to do - it does not weaken the joint at all. Further, the hard crust of the lasered hole tends to wear only one spot on the countersink cutter - in my day job designs I vary the "pilot" hole diameters to spread the wear on the cutters. But I avoided doing that in the MM designs because there would have been too many questions.
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  #144  
Old Sun 30 August 2009, 08:46
Castone
Just call me: Leo #41
 
Soddy Daisy , Tn
United States of America
Belt drive

In the drawings I will under size the bearing hole as it is fairly easy to open it up , with hand tools. I did have to play with the kerf to get this cut, but was repeatable. I think I may start offering these in the kits, which would be real low cost way of building a belt drive and could be built by most all MechMate builders. And as I mentioned before since the bearing flanges are inside and there is a bushing on each side of the pulley that rides on the inner race of the bearing. The press fit only needs to be tight enough to keep the bearing housing from spinning and yes a little green loctite would not hurt anything. So far everthing is working very well.
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  #145  
Old Wed 16 September 2009, 03:03
obuhus
Just call me: Dmitriy #68
 
Kirov region
Russia
September 2009. Has begun assemblage belt-drive.
Many thanks to Gerald for the help with step-motors. After long searches and reflexions I have decided to go the checked up road, but have a little changed a traditional design of the mechanism of a reducer.
Reducer classical 3:1 (pulleys LS27T5/20-2, LS27T5/60-0, a belt 16T5/355). Has more low loaded drawings in dxf. It is not accurate a little - forgive, I only have started to study AutoCAD.
Attached Images
File Type: jpg IMG_4211.jpg (36.5 KB, 2352 views)
File Type: jpg IMG_4218.jpg (17.7 KB, 2340 views)
File Type: jpg IMG_4221.jpg (18.0 KB, 2338 views)
File Type: jpg IMG_4226.jpg (20.9 KB, 2340 views)
File Type: jpg IMG_4227.jpg (17.5 KB, 2345 views)
File Type: jpg IMG_4229.jpg (17.3 KB, 2349 views)
File Type: jpg IMG_4230.jpg (16.9 KB, 2345 views)
File Type: jpg IMG_4233.jpg (21.7 KB, 2344 views)
Attached Files
File Type: dxf Obuhus-BeltDrive.dxf (328.2 KB, 315 views)
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  #146  
Old Wed 16 September 2009, 03:09
sailfl
Just call me: Nils #12
 
Winter Park, FL
United States of America
Dmitiry,

Looks like you have a great start and Welcome to the site.

Though it may seem like you need to have lots of fans to combat the heat, the one fan works find. I agree with Irfan.

Your rails and belt drives look great. Keep taking pictures, we like to see what others are doing.
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  #147  
Old Wed 16 September 2009, 04:22
javeria
Just call me: Irfan #33
 
Bangalore
India
I love your reduction drive - good thought given to it.
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  #148  
Old Wed 16 September 2009, 08:41
javeria
Just call me: Irfan #33
 
Bangalore
India
G' I think seriously we should standardize this design for the reduction mechanism. Its metal laser cut welded and no bends reqd and can order a special shaft and pinion combined. Also we can avoid all nut's by tapping the motor plate by making it 6mm thk, that way we can use screw of upto M6.

ok nuts are reqd to adjust the belt tension a bit
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  #149  
Old Wed 16 September 2009, 09:25
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Dmitriy's design seems to have all the bearings (or one wide bearing) on the outboard side of the reduction unit.
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  #150  
Old Wed 16 September 2009, 09:40
javeria
Just call me: Irfan #33
 
Bangalore
India
yes thats what I like too - hmmm is that wrong, ???? I feel it would be ok - I think one more of our forum member has done this already.
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