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Inventor General Discussion

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CCrabtree1
Posts: 19
Registered: ‎03-04-2009
Message 1 of 12 (304 Views)

Concave rack

304 Views, 11 Replies
06-03-2013 10:06 AM

I need to make a rack for a machine I am designing.  We use a variation of this now but I need to change the rack we have always used.  The rack is on a radius and the teeth are on the inside of said radius.  I plan on using the same tooth profile that we are currently using but i was wondering if there was an easy way to pattern this.  Any ideas or suggestions will be greatly appreciated.  Thanks in advance.

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rdyson
Posts: 918
Registered: ‎04-11-2005
Message 2 of 12 (292 Views)

Re: Concave rack

06-03-2013 11:24 AM in reply to: CCrabtree1

A curved rack is a gear, in your case an internal gear. The teeth on a rack are trapizoids, on a gear they are somewhat more compicated.

Depending on your requirements the trapizoidal teeht might be acceptable. Without more information, we can't give any advice.

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CCrabtree1
Posts: 19
Registered: ‎03-04-2009
Message 3 of 12 (284 Views)

Re: Concave rack

06-03-2013 12:06 PM in reply to: rdyson

Thanks for your reply rdyson.  I am attaching the "print" I am starting with.  I don't know how much its going to change but I thought I would do a little prework before it gets dumped on my lap.  The is attached to a base plate and then a Marin S312  drive gear on a gearbox moves the machine around a pivot. 

 

thanks again

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blair
Posts: 4,494
Registered: ‎11-13-2006
Message 4 of 12 (282 Views)

Re: Concave rack

06-03-2013 12:10 PM in reply to: CCrabtree1

I might look at a Planetary gear assemby and only use a portion of the outer gear ring.

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CCrabtree1
Posts: 19
Registered: ‎03-04-2009
Message 5 of 12 (277 Views)

Re: Concave rack

06-03-2013 12:22 PM in reply to: blair

blair, could you elaborate a bit more. 

thanks

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rdyson
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Message 6 of 12 (267 Views)

Re: Concave rack

06-03-2013 01:09 PM in reply to: CCrabtree1
The info I'm talking about is like speed, torque, cycles, etc
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blair
Posts: 4,494
Registered: ‎11-13-2006
Message 7 of 12 (262 Views)

Re: Concave rack

06-03-2013 01:18 PM in reply to: CCrabtree1

A curved rack, rather than a linear rack could be described as a Planetary Gear set but with only a single spur gear and a ring gear. All you need is a portion of the ring gear. All the gear teeth profile data is easily accesable for these gear sets.

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JDMather
Posts: 28,258
Registered: ‎04-20-2006
Message 8 of 12 (257 Views)

Re: Concave rack

06-03-2013 01:38 PM in reply to: CCrabtree1

CCrabtree1 wrote:

i was wondering if there was an easy way to pattern this. 


Circular Pattern feature?

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CCrabtree1
Posts: 19
Registered: ‎03-04-2009
Message 9 of 12 (196 Views)

Re: Concave rack

06-05-2013 08:18 AM in reply to: JDMather

I appreciate all your input guys.  Let me respond to a couple of these: rdyson, the speed and cycles are non factors, the speed is very slow and the the cycle is only every so often when the operator makes the machine pivot so it could be once an hour or once a week, but either way not anything that could be considered a cycle and I can't really figure the torque right now without it being a guess becasue this machine is still in development.  blair, great idea about finding the Planetary gear set but the problem I am having with that is I cannot find a set that even comes close to the parameters I know.  JDMather, I would love to use the circular feature for this but as I stated in the answer to blair, this rack and pinion seems to be custom so finding just the right value to make everything come out right is eluding me.  A straight rack is simple and is logical, the what seems to be a custom rack on a radius is making me crazy.  Thanks again for all the help.  I apoligize for my ignorance also  :smileyhappy:  

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blair
Posts: 4,494
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Message 10 of 12 (193 Views)

Re: Concave rack

06-05-2013 08:28 AM in reply to: CCrabtree1

A good gear book or possibly the Machinist Handbook will provide the data required. I would model the single tooth profile on the curved rack at one end and then as JD mentioned, pattern it to create the remainder of the teeth. 

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