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fabrica
Registered
Username: Daya
Post Number: 8
Registered: 10-2006
| | Posted on Saturday, November 04, 2006 - 04:57 pm: | 
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Can some one give me details of a U.S.A. manufacturer/Stockist of good quality Racks & Pinions. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 372
Registered: 11-2005
| | Posted on Saturday, November 04, 2006 - 05:22 pm: |
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The MechMate gear pinions and racks come from Chiaravalli Trasmissioni S.p.A.. See Spurgears and Racks on this page. Good chance they have a stockist in your country. Look for module 1 (small teeth) and 2m long (or longer) racks. All in steel. My price here is about €20 for a 2m length of rack and €2 for a 23 tooth pinion gear.
If you contact them, they might tell you if they have a stockist in the USA.
"For Gears & Racks in the USA, look to Boston Gear 0.5" square rack, (0.5" gear face width), 20 pitch, about 20 tooth pinion, 20 degree pressure angle <-- the three 20's are coincidental, they mean different things Metric guys will look for module 1, 20 degree pressure angle and about 25 teeth, face width 15mm and 15mm square rack. Atlanta Drive Systems Metric. Made in Germany, represented in USA, Spain, Italy, England, Singapore.
Vadeem gave us this link to save everybody in USA some time(page 38):
http://bostongear.com/pdf/catalogs/P-1482-BG_cat-OpenGearing.pdf (5.3MB pdf)" |
Dirk Hazeleger
Registered
Username: Dirk
Post Number: 44
Registered: 12-2005
| | Posted on Sunday, November 05, 2006 - 08:04 am: |
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Best place I've found rack in the US. About a third the cost of others
http://www.stdsteel.com/gear.htm
Dirk |
Gerald_D
Registered
Username: Gerald_d
Post Number: 374
Registered: 11-2005
| | Posted on Sunday, November 05, 2006 - 08:22 am: |
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That's useful Dirk. I see they only do rack and not pinions. Just a note to tell everyone it is no problem to mix the suppliers of rack and pinion - as long as you specify pitch, pressure angle and width. |
fabrica
Registered
Username: Daya
Post Number: 10
Registered: 10-2006
| | Posted on Sunday, November 05, 2006 - 09:41 am: |
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I have gone through the Boston gear catalouge. As per your specs mentioned in anothe thread I assume I have found the correct pinoin and rack. For the Pinion the Catalogue page no is 30 and the item code is 46133. For the Rack the Cat page number is 35 and the item code is 12760 (6 foot lenth). If you have the time can you please conform this so that I do not make a expensive mistake. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 378
Registered: 11-2005
| | Posted on Sunday, November 05, 2006 - 10:22 am: |
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Fabrica, so you want me to make the expensive mistake for you? 
Your selection looks 100%. You will need 4 pinions and enough rack for 2 x-rails, 1 y-rail and 1 z-rail.
Also see this paragraph on page 150:
You can decide later if you want to use them soft or hardened. The soft condition is okay for a few month's use. (You cannot buy them already hard - that is your own responsibility after boring out and cutting the threads) |
fabrica
Registered
Username: Daya
Post Number: 11
Registered: 10-2006
| | Posted on Sunday, November 05, 2006 - 01:30 pm: |
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Understood thanks, I will have that hardening part in mind. |
Greg Waggy
Registered
Username: Gawnca
Post Number: 13
Registered: 11-2006
| | Posted on Thursday, November 09, 2006 - 10:00 pm: |
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I know that with ACME threaded rod or just about every other type of drive system there is back lash that has to be compensated for. How it is overcome with rack and pinion? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 423
Registered: 11-2005
| | Posted on Friday, November 10, 2006 - 09:11 am: |
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The MechMate pinion gears are spring-loaded against the racks - there is zero backlash. But, there is more rubbing and friction between the teeth than what the gear purists would like. (The rubbing actually keeps the gears clean). You won't believe it till you've tried it, but these rack & pinions work maintenance free, even in very dusty environments. If the pinions are not hardened, you can get about a year's life out of them. I hardened a set 2 years ago and they are still going strong. Backlash only develops when the pinion gears wear out. |
Greg Waggy
Registered
Username: Gawnca
Post Number: 18
Registered: 11-2006
| | Posted on Friday, November 10, 2006 - 05:03 pm: |
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Gerald, Do you have a photo of this spring-loaded mount? I'm trying to get all my ducks in a row before setting out to build. Thanks again!
Greg |
Gerald_D
Registered
Username: Gerald_d
Post Number: 426
Registered: 11-2005
| | Posted on Sunday, November 12, 2006 - 05:30 pm: |
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These drawings show the assemblies:
M510100AA.pdf
M510200AA.pdf
(they will be included in the next revised batch of downloads in due course and the links from here will stop working)
The motor (or motor & gearbox)is screwed to the Motor Plate M5 10 012 D which is hinged to the car. The spring holds the pressure of the pinion gear against the rack. The stabiliser screw rides in a slot - it allows the motor plate to swing but not "flap" around. Teflon washers are fitted where the motor plate slides against the car. |
Greg Waggy
Registered
Username: Gawnca
Post Number: 19
Registered: 11-2006
| | Posted on Sunday, November 12, 2006 - 08:17 pm: |
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Gerald, Thanks a lot. I guess I better save these so I'll know what I'm looking at. This is a very cool looking design. I am finding that racks and pinion gears are VERY costly here in the U.S.
One more question, what is the gear ratio on your system? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 428
Registered: 11-2005
| | Posted on Sunday, November 12, 2006 - 08:44 pm: |
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Right at the top of this thread I mentioned how much I am paying for rack & pinion made in Italy, shipped to South Africa and marked up by the importer/stockist. I can't see why you should be paying much more than that? (very roughly $20 for a 6ft length of rack and $2 for a 23 tooth pinion gear)
My pinions are 24 tooth metric module 1. That means one revolution of the pinion equals 75.4mm [2.97"] |
Greg Waggy
Registered
Username: Gawnca
Post Number: 21
Registered: 11-2006
| | Posted on Sunday, November 12, 2006 - 08:48 pm: |
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The price I could find for a pinion gear was $23.40 each. Still looking for a better supplier. That was from a distributor of Boston gearing. |
Mike Richards
Registered
Username: Richards
Post Number: 54
Registered: 05-2006
| | Posted on Monday, November 13, 2006 - 02:45 am: |
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McMaster-Carr supplies my spur gears. They also sell 6ft lengths of rack. Page 985 of their catalog shows the current price of 6ft 20-pitch rack at $40.60. 20-pitch 20-tooth, 25-tooth and 30-tooth gears are $13.02, $13.55 and $14.88 respectively. |
Greg Holt
Registered
Username: Greolt
Post Number: 1
Registered: 08-2006
| | Posted on Wednesday, November 15, 2006 - 01:28 pm: |
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I am looking to build a scaled down Mechmate, or very similar to it. X-1200 Y-900 (I think)
Localy (Australia) I can get rack 12.7mm wide at module 1.5 or .5" wide at 16 pitch off the shelf. Both are 20 degree and mild steel.
Now I see that Gerald is recomending 20 pitch. What do you think?? Does it matter much??? |
Gerald_D
Registered
Username: Gerald_d
Post Number: 453
Registered: 11-2005
| | Posted on Wednesday, November 15, 2006 - 02:41 pm: |
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The minimum pinion teeth count should be about 20, so that the spring-loaded pinion rolls relatively smoothly on the rack. 20 tooth pinions with module 1.5 or DP 16 are starting to give lots of linear travel for small rotations. I would search further to find finer gears. But, in a pinch, they will work. |
Greg Holt
Registered
Username: Greolt
Post Number: 2
Registered: 08-2006
| | Posted on Wednesday, November 15, 2006 - 11:33 pm: |
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OK therefore because I plan to use a timing belt reduction I take it that the pitch issue is not so compelling.
I was cheeky enough to ask the makers of the EZrouter what rack they use and they replied 14 degree hardened (didn't give a pitch)
Everything I have read says use 20 degree.
About being mild steel - do you use mild steel rack with hardened pinion? Or both hardened?
I suspect it would be prefferable to have hardened rack with soft pinion and think of the pinion as sacrificial rather than the other way round. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 459
Registered: 11-2005
| | Posted on Thursday, November 16, 2006 - 06:50 am: |
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14 degree was a popular face angle (the side of a rack tooth is flat and it leans at the face angle) with the inch guys. The metric world standardised at 20 degrees. Even the inch guys are swinging to 20 degrees now.
A 20 tooth pinion works against a rack with about 600 teeth. If the materials were equally hard, the rack will last 30 times longer than the pinion. For short racks, it might make sense to have hard racks/soft pinions, but racks are cheaper than pinions if you take number of teeth per dollar. |
Greg Holt
Registered
Username: Greolt
Post Number: 3
Registered: 08-2006
| | Posted on Thursday, November 16, 2006 - 09:48 am: |
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So Gerald are you using mild steel racks or hardened? What have the ShopBots been using?
Reread through this post and am still not sure 
Thanks. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 460
Registered: 11-2005
| | Posted on Thursday, November 16, 2006 - 11:29 am: |
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Every router that I know of uses the plain, basic, unhardened steel racks. MechMate & ShopBot included. The correct name probably isn't "mild" steel - mild steel is typically un-hardenable with a carbon content less than 0.3%
Chiaravalli say they use C40 for racks and C45 for pinions - "medium carbon" steels. |
Greg Holt
Registered
Username: Greolt
Post Number: 5
Registered: 08-2006
| | Posted on Thursday, November 16, 2006 - 12:29 pm: |
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Thanks for that Gerald
The only supplier that I have found so far here lists their "off the shelf" racks as mild steel and pinions as S1045
Of course they will make anything I want but off the shelf is dear enough.
I've asked Chiaravalli by email if they have a distributor in Aus. but no answer.
Mcaster Carr won't sell to us here. |
Gerald_D
Registered
Username: Gerald_d
Post Number: 462
Registered: 11-2005
| | Posted on Thursday, November 16, 2006 - 01:42 pm: |
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Cape Town is only the 3rd or 4th biggest industrial city in South Africa, yet I have a choice of 3 gear/rack stockists. None of them are listed in any directory as gear/rack suppliers, but they are all listed as sprocket/chain suppliers - maybe the same situation applies there? Grab the Yellow Pages and look for power transmission, conveyors, material handling component suppliers. If someone tells you they don't have what you are looking for, that is a golden opportunity to ask them to suggest someone else. That's why I like shopping by phone, rather than "mailorder", you get these references of who does what. |
Greg Holt
Registered
Username: Greolt
Post Number: 6
Registered: 08-2006
| | Posted on Thursday, November 16, 2006 - 10:44 pm: |
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Thanks very much for the advice Gerald and Greg.
I will cast my net a bit wider. |
DocTanner
Registered
Username: Doctanner
Post Number: 4
Registered: 11-2006
| | Posted on Saturday, November 18, 2006 - 12:00 am: |
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As Dirk pointed out http://www.stdsteel.com/gear.htm is the cheapest around. 4 - BF200011 20dp 20 degree 6' racks $23.20 each. Ordered on the 13th.Received the 24th. They don't take credit cards. Mailed check to them and still got quick delivery time. |
Driving Mechanisms: Rack/pinion, gears, screws & chains