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Concave rack

11 REPLIES 11
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Message 1 of 12
CCrabtree1
573 Views, 11 Replies

Concave rack

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.

Windows 7 64 bit
16 GB ram
Intel i7 2600 3.4 ghz
AMD radeon HD 6450
PDSU 2013
11 REPLIES 11
Message 2 of 12
rdyson
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.



PDSU 2016
Message 3 of 12
CCrabtree1
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

Windows 7 64 bit
16 GB ram
Intel i7 2600 3.4 ghz
AMD radeon HD 6450
PDSU 2013
Message 4 of 12
blair
in reply to: CCrabtree1

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


Inventor 2020, In-Cad, Simulation Mechanical

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Message 5 of 12
CCrabtree1
in reply to: blair

blair, could you elaborate a bit more. 

thanks

Windows 7 64 bit
16 GB ram
Intel i7 2600 3.4 ghz
AMD radeon HD 6450
PDSU 2013
Message 6 of 12
rdyson
in reply to: CCrabtree1

The info I'm talking about is like speed, torque, cycles, etc


PDSU 2016
Message 7 of 12
blair
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.


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
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Delta Tau Chi ΔΤΧ

Message 8 of 12
JDMather
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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Message 9 of 12
CCrabtree1
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  🙂  

Windows 7 64 bit
16 GB ram
Intel i7 2600 3.4 ghz
AMD radeon HD 6450
PDSU 2013
Message 10 of 12
blair
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. 


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
Did you find this reply helpful ? If so please use the Accept as Solution or Kudos button below.
Delta Tau Chi ΔΤΧ

Message 11 of 12
rdyson
in reply to: CCrabtree1

Given your speed and cycles, trapezoidal teeth might be okay. You will incur wear on either the gear or the 'rack' teeth (depending on which is softer) but it might be acceptable since it will not require repair often enough to be a bother.
Per JD, model the curved bit, add a trapezoid tooth and pattern it the appropriate distance around the curve.


PDSU 2016
Message 12 of 12
CCrabtree1
in reply to: rdyson

Well I appreciate all the advise guys.  I am attaching my finished product.  I decieded to do it as an assembly just to make it easily adjustable if need be.  It was a little time consuming but now if i need to change it or adapt it to another radius it will be rather easy.  Thanks again.

Windows 7 64 bit
16 GB ram
Intel i7 2600 3.4 ghz
AMD radeon HD 6450
PDSU 2013

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