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  #1  
Old Thu 22 October 2009, 00:15
sprayhead
Just call me: Francis
 
sydney
Australia
Considering using modulus 4!! yahoo, rack and pinion

Hi,

I have made some tests with a mod. 4, 13 tooth, 52mm pitch diameter, AISI1045 steel, black oxide finished pinion and a Nylon rack.

The test consisted of myself grabing the pinion by hand and rolling it over the rack forward and back while applying different pressures on the pinion against the rack. Guestimation tells that I have applied 5-15 kilos of pressure on the pinion. Since I was using a shaft through the pinion, it was easy to push it down against the rack.

The primary conclusion is that it runs very smooth and quiet, and it definitely improves as the pinion and rack further adjust. I was impressed. For some reason I thought that it was going to run rough and "vibrate" going up and down.


The rack costs only 25 bucks for 1000mm lengths and the pinion only about 5 dollars each, ordered straight from a factory in china. The rack is made of nylon, injection moulded, it has an internal steel flat bar running length wise for reinforcing and the quality looks nothing short of good. I did not test for pitch discrepance over lenght but I guess that if the mould was properly designed it wont be a problem.

I did extensively try to get a smaller modulus rack with but at this price I couldn't find anything but modulus 4.

If anyone is interested in giving it a try, let me know, I am just about to order 20 pinions.

The rack is very easy to find... It's made for gate automation. The particular rack that I have used was designed here in Australia.

Francis

Last edited by sprayhead; Thu 22 October 2009 at 00:43..
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  #2  
Old Thu 22 October 2009, 22:57
lunaj76
Just call me: Justin #24
 
Littleton, (Colorado)
United States of America
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Francis,

Sounds interesting. How much different is the diametric pitch of this rack verses the one that is recommended. I have thought that a nylon rack might give less vibration. Would there be a seam to deal with?
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  #3  
Old Thu 22 October 2009, 23:05
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
The pitch of module 4 is exactly 4 times greater than module 1
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  #4  
Old Fri 23 October 2009, 01:37
sprayhead
Just call me: Francis
 
sydney
Australia
Hi

Joining the racks looks like it is piece of cake. they come with a little slot on the ends that will probably help to some stage with the alignment. Ultimately the best trick will be to use a small piece of rack and use it to "syncronize" the two lenghts being joined.

The fixing can be done by above, as per MechMate style or by the side of the rack. The racks I got come with 8 holes (about 6mm dia.) for side assembly.
For MachMate style one has to make the holes... there is one catch. The steel in the rack style I got is actually a flat bar, 12x5. It might be a little tricky to get a hole right in the middle of the 5mm face of the flat bar... only trying will let us know how tricky. There is another style of the GateDoor racks that actually has a square bar inside, 10x10. That would make it easyer.

I'll post results... I'm still sorting out the special spur gears at the moment. The stock (48 or 52mm P.D.) spur gears all have 40mm tooth width and 20mm hub width, It's way too much, as this rack is 22mm wide. I'm trying to get some made with 20mm tooth width and 10mm hub width. I might be getting lucky just in a few days.

atb,
Francis
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  #5  
Old Fri 23 October 2009, 17:06
AuS MaDDoG
Just call me: Tony #71
 
Brisbane
Australia
Hi Francis,

Sounds interesting keep us posted, some pics would be nice

Cheers
Tony.
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  #6  
Old Fri 08 January 2010, 04:32
sprayhead
Just call me: Francis
 
sydney
Australia
Gerald

Gerald,

I'd kindly like to ask you to raise my upload .jpeg and .jpg data allowance to 400Kb, if possible.
I've got about 5 pics I'd like to upload.


Thanks,
Francis
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  #7  
Old Fri 08 January 2010, 04:40
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Sorry Francis, but you will have to resize your pics. Mail them to me gerald at mechmate dot com and I will do it for you.
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  #8  
Old Fri 08 January 2010, 08:57
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
Seach through the forum and you can find links to tools to resize the pics. You can also open the PICS in Microsofts Paint program and select images then under "Stretch Skew" you can resize.
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  #9  
Old Fri 08 January 2010, 10:46
lumberjack_jeff
Just call me: Jeff #31
 
Montesano, WA
United States of America
... or use photobucket.
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  #10  
Old Fri 08 January 2010, 11:58
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
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On my laptop ( with XP ) I right click on the picture and click on SEND TO..... Mail Recipient. The next window pop up and ask if it can make the picture smaller.... I click YES and the Outlook Express window for generating a new e-mail pops up. I copy this smaller picture file to somewhere and use this on the forum....Brings a 3 Meg file to the 65 k size and quality is good.
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  #11  
Old Fri 08 January 2010, 13:22
sprayhead
Just call me: Francis
 
sydney
Australia
thanks guys!

They way that I did it, when I am not lazy is to do that with IrfanView, it's a great picture viewer. In there you can batch resize and rename, it's very handy and it gives great results keeping image quality as it has a special algorithm for Jpegs.

Anyway, there is the rack and the custom pinions that I was talking about, they run quite smooth on the rack. I think that it will already do for me.

Next order I will try the next size smaller pitch diameter pinions (48DP) and ask them to grind the pinion tooths to 3 triangles (~0,8Ra).
As you can see on the picture the surface finish on the tooths is straight from the lamination process. Not bad but not like a ground surface.

Those pinions were cut off of what they call "gear wire" or something like that.

The motors are from MS Motor. I had to look in the gearbox... Posted for the curious minds out there:-)

F.
Attached Images
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Last edited by sprayhead; Fri 08 January 2010 at 13:29..
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