# Gear Train Calculator



## evan-e-cent (Nov 30, 2021)

Does writing software count as a "Project"?   Well if it does I would like to tell you about a program I wrote for lathe users. RideTheGearTrain.com 

It was designed to tell you how to set up the gear train to cut any thread. When it runs it usually gives you a long list of different ways you can set up your gear train.  Beside each setup there is a button labeled DRAW. Click that and it produces a scale drawing of the gear train so that you can spot any problems that might occur.  





The data input is in 5 steps and then you run the program.
(1) First choose your lathe.
(2) Enter the set of gears that you own.
(3) Choose what type of thread you need: metric, imperial or feed rate
(4) Enter the % error you are willing to accept in the final thread. It may be zero or perhaps 2%.
(5) Enter the pitch of the thread you require. Actually there are 3 ways you can do this:
    (5A) Simply enter the pitch or TPI
    (5B) Enter a range of values to produce tables
    (5C) Look up a reference table eg metric or UNC etc.
(6) Finally click RUN.

If you choose option 5C the reference tables provide a lot of extra information which allows the program to display "Thread Specifications" after the list of gear trains. This includes two tables of possible metric or imperial drill sizes that could be used for the thread you chose. Not just a single drill size that most tables give you. I have been adding calculation of the stress on the bolt and thread when tightened to a given torque (under construction).

It will work for any lathe without a gearbox, including mini-lathes. For lathes with a gearbox it needs to know the gear ratios. There is a list of about 25 lathes with gearbox data included.  It was originally written for Boxford and other SouthBend 9A clones so if you have a clone choose a "Norton" gearbox. Myford is included and so are a few other models like Colchester, Chester, Nile, Hendley, Precision Mathews etc. If you want your lathe added please contact me or look up "Custom Gearbox" at the end of the list of lathes.

There are extensive help files with help button beside each input box.

There are 3 Youtube tutorials listed below the menu.
My email address is listed at the top of the info, above the menu.

Keep in mind that I am not an engineer - my only training was 4 years of engineering in High School with my father as the teacher.
Let me know if you have any questions or discover any problems or flaws.

PS it does not cost you a cent and there are no hidden costs.
I hope you find this useful.  Enjoy!
Evan


----------



## Weldingrod1 (Nov 30, 2021)

An excellent project!

Sent from my SM-G892A using Tapatalk


----------



## RJSakowski (Nov 30, 2021)

Very much a project!  I have dabbled a bit in finding possible gear variations for the Grizzly G0602 lathe using a spreadsheet and a spreadsheet for calculating depth of cut using a 29º compound feed for common Imperial and metric pitches but haven't put them together in a single package.

I haven't done much in the past two years as I have added an electronic lead screw to my lathe, eliminating the need for any gears.

I haven't delved deeply into your program but one thing that I noticed offhand is that when I entered the G0602 into type of lathe, it enters 8 tpi as the lead screw pitch.  The G0602 has a 12 tpi lead screw. I will review your program more deeply after I've had my coffee.

I'm sure you will find plenty of beta testers on this forum.


----------



## cwilliamrose (Nov 30, 2021)

I started to enter the data for my lathe but found it was going to be pretty involved and I wasn't sure of all the terms being used. I did look at the tutorial and I now have a better idea of how to proceed. When I get the time I may try again to get mine entered and check the results against the spreadsheet (specific to my lathe) I created years ago. The spreadsheet is more of a manual process which could take some time to go through for a given pitch. I originally needed a 3.3333 TPI solution which is why I did the spreadsheet. Turned out there were several solutions that were very close and after a bit more trial and error I found a couple of exact solutions. Having the computer do the work would be a very nice option.


----------



## evan-e-cent (Nov 30, 2021)

Hey, THANK YOU both for the feedback.  I have been through many iterations of input design trying to make it easy to use. Let me know if there are any areas that are particularly confusing.  Long chunks of text explaining things should help, but tend to make it look more complicated and 'forbidding'.

RJS, this is the kind of information I need to expand the usefulness of the program for people who have a gearbox. Each case has to be entered separately, although, if your lathe is otherwise identical to another Grizzly lathe you will have noticed that you can change the leadscrew pitch setting. 

The easiest way to proceed would be to ask you to send a photo of the gearbox label showing the threads it can cut.  I also need to know the gears that are used with the gearbox but I think these will be included in the thread tables.

I just ran the program and see what you mean. I have split the entry for Grizzly lathes into two models so that 0602 is listed separately with it's 12 TPI leadscrew (DONE).  But then I need to check that it is giving correct results and for that I need the info from the gearbox labels. 

Could you send them using the email address listed at the top, above the menu when you run the program.  You might like to check it yourself now that the G0602 is listed with a 12 TPI leadscrew. I expect it will give incorrect answers until I change the "primary ratio" of the gearbox. This is a factor that I multiply all the gear ratios by.

I wonder how many different Chinese lathes there are with gearboxes!  Perhaps I should ask on the Grizzly page.   I am afraid to ask.  Many of these complex gearboxes take me a day or two to decipher!  I hope the G0602 is similar to the G0752. 

Thanks


----------



## RJSakowski (Nov 30, 2021)

As far as I know, the G0602 and G0752 only differ in the spindle drive.  The lead screw and gear box should be the same.  The on line user's manual actually covers both lathes.
Here is the chart that I made for the 602 gearbox.

Gear Box Ratio (Out/In)III CII CI CIII AII AI AIII BII BI B0.58330.4166670.51.16670.83333312.33331.6666672

And here is a threading table listing most possible Imperial combinations (not mine, from the internet, unknown source).  I say most because the the 104, 120, and 127 tooth gears aren't brought into the mix.


I hope this helps.


----------



## evan-e-cent (Nov 30, 2021)

Thanks for this.  So I guess both of these lathes have a leadscrew with 12 TPI.
When you say the only difference is in the spindle I assume you are referring to spindle speeds.
I assume the number of teeth on the spindle gear are the same - 40T.
I have put them both into the program now as separate lathes.

I wasn't absolutely sure what the gear ratios you listed meant so I derived them myself and got the same answers!
I looked up 12 TPI on this table and calculated the gear train ratio and it was 1.0
The overall gear ratio has to be 1 to cut the same thread as the leadscrew.
Therefore the gearbox setting A1 must also have a gear ratio of 1.0
From that I can calculate all the gearbox settings for the program.
From the table:

1B = 6TPI
1A = 12 TPI
1C = 24 TPI

So relative to A1=1 the ratios (in terms of TPI, not gear ratios) are
1B=0.5
1A=1
1C=2

Lets look at the number lever - With the same gear train a=60 b=40

Actually the online table shows the gear ratios in the grey panels on the left and your message contained the same.
1A = 12 TPI  Ratio =1.0000
2A = 14.4 TPI Ratio 0.83333 = 12/14.4
3A = 10.29 Ratio 1.1667   = 12/10.29

However my program uses "F-factors" for the gearbox and these are proportional to TPI which are the inverse of gear ratios! 
That way the table looks like the TiP table on the gearbox in most cases.

So I have to invert these ratios as follows:
1A = 12 TPI  Ratio =1.0000
2A = 14.4 TPI Ratio 0.83333 = 1.2
3A = 10.29 Ratio 1.1667   = 0.8571428

This gives me everything except a calibration factor that i call Primary Ratio of the gearbox.  In my program I use the equation:

TPI = primaryRatio x GearboxRatio x Leadscrew / GTR

Re-arranging to get the Primary Ratio

primaryRatio = (TPI x GTR) / (GearboxRatio x Leadscrew)

We know the data for several threads but I like to use the one that is the same as the leadscrew, so they cancel:

primaryRatio = (12 x 1) / (1 x 12) = 1

primaryRatio =1, so in fact no correction is required in this case.

I have entered these specs in my program. 

I had already split G0602 from G0752 so I will leave them as separate entities, but now the specs are identical.

Could you try it out and see if it looks correct. I have included the extra change gears you suggested. Of course the 127/120 combination gives you metric conversions so the program should give you metric threads.

It is interesting that the G0750G is totally different and very complicated.


----------



## Just for fun (Dec 1, 2021)

Very cool stuff.   Thanks for sharing! 

Tim


----------

