Need to define a spur gear with a specified distance between axels

[Kent Swan]

Okay, I need to define a spur and pinion gear that are precisely 0.70 inches apart with a gear ratio of 2.5:1 with all the other parameter s falling where they will. Any clue how to do this in gearotic.  I cannot seem to define an axel distance and a tooth ratio and get useful specs.

[BobL]

Ken;

 Have you tried the gear calculato r, ?? icon left side in spur gear tab, just a suggestio n.

Cheers
Bob

[ArtF]

Well, the gear calculato rs stil dont work very well for that sort of question. . so here's how I do it..

 You want a ratio of 2.5.. so the first question is how many teeth do you want on the pinion gear. ( lowest tooth count...)
Since you want a ratio of 2.5, you want an even number count. Its best to keep a spur gear above 8 teeth.. 12 if you can just
as a matter of design.. but lets say you want 8..

  So set a pinion of 8 teeth, 2.5 times that is 20, so set a 20 tooth wheel..

 So now you have your ratio of 2.5:1 .. so all you need now is to find out what DP is appropria te for a center distance of .7"..
I slowly raise my DP till I get the distance I want.. in your case its a dp of 20.0 0to get exactly .7" between centers..

 You may want o slightly offset that to get some backlash availabli ty.. but thats the way I quickly find a center I need. Eventuall y the calculato r will do much of that for you as soon as I figure out the best way to do that without confusing the heck out of you..

Art

[ArtF]

By the way.. Those are damn small gears.. , youd probably need EDM to make such a small gear.. or very small machine tools as well as very very small hands.. lol

  The reason the calculato r fails in this is its very hard to compute all the factors from scratch, there are infinite possibili ties.. Im looking into a more heuristic solution algorithm, and its on my list for the upcoming developme nt seasons work. Im hinking along
the lines of a wizard of soem sort that can guide you to such a  solution. .

  I develop GM is 1-2 developme nt periods during the year, the next will probably be late August or September, Im working hard on CNC software timers at the moment to see if I can crack the 64 bit system driver history. I may get to GM again earlier than above, and I fix bugs at all times, but feel free to ask about better solutions at any time, as it lets me consider the order in which to develop as I get back to it.

Art

[Kent Swan]

Thanks for the input.  I looked for the spur gear design panel button but it seems to be not there on the most recent version I down loaded.

Most of what I do is small to very small to miniature .  A gear over an 2 inches is huge for me. 

My gears are cut from plastic like delrin or metal like steel or brass. Some gear sets are custom designed while others need to match up with existing gears.  While I can hob gears on my CNC equipment, I don't generally do the gear cutting myself but send out the specs to a professio nal house to have them cut.

I've started trying using Gearoitic to design in order to get the specifica tions nailed down.   In this particula r case the tooth counts are 40 and 16  (2.5:1) with a center to center distance requireme nt of 0.7 inches.   

I've used other gear calculato rs which, given a tooth pressure angle, the tooth ratio and the distance between axels will give you the the tooth profile and depth requireme nts which give decently meshed gears.

The one approach noted is a successiv e approxima tion method and, for my purposes, pretty much a waste of energy.  I've also noted on the spur gear calculato r that it gives the same dp for both gears regardles s of the tooth ratio.  This appears to be a bug.

Kent

[ArtF]

Kent:

>>I've used other gear calculato rs which, given a tooth pressure angle, the tooth ratio and the distance between axels will give you the the tooth profile and depth requireme nts which give decently meshed gears.

  Yeah, thats likely the design I'll aim for. Though I doubt Ill put any stubbing adjusteme nts in there, Ill likely just have it calculate the DP or MOD for the distance and tooth ratio applied..

Art

[Kent Swan]

Art

That would probably be fine.  The idea is to get everythin g in the close ball park quickly and accuratel y then use the other controls to 'tune' the gears.

Kent