Author Topic: 2:1 Helical gears for Mastiff  (Read 13680 times)

Offline ozzie46

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2:1 Helical gears for Mastiff
« on: May 31, 2013, 03:05:19 PM »
 

  I'm having a great deal of difficulty finding a pair of 2:1 skew gears for my Mastiff build. The gears are .6250 overall dia for both of them 32 DP, 8 tooth on one with a bore of .3125.  hub is .4375 by .1875. Gear width is .1875 by .6250 dia. This is the crank gear.

 The oil pump/contact breaker shaft gear is 32 DP, 16 tooth. Hub dia is .4375 by .1562 width.  gear face is .1875 width by .6250 dia. Shaft bore is .250.

 L.C. Mason described them as "2-1 Rating Special Spiral Gears" and he got them from a company cxalled "Bond O" Euston Road" catalogue No C.185. I guess they are no longer in business.


 Any help would be greatly appreciated. Any advise on what to substitute would help also.
  The cost of having a pair specially made is prohibitive.

  Ron

Offline Jasonb

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Re: 2:1 Helical gears for Mastiff
« Reply #1 on: May 31, 2013, 03:13:28 PM »
Have a word with Hemmingway they sell the gears as part of the casting kit and may be able to supply on their own or say who they get them from

http://www.hemingwaykits.com/acatalog/The_Mastiff___L_C_Mason.html

Offline JimG

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Re: 2:1 Helical gears for Mastiff
« Reply #2 on: May 31, 2013, 03:55:03 PM »
Bonds actually closed down just over two years ago and they were still supplying their model engineering parts up till then.   You might have some luck following the lead on this web page.

http://modelengineeringwebsite.com/Bonds_OEuston_Road.html

Jim.

Offline IanR

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Re: 2:1 Helical gears for Mastiff
« Reply #3 on: May 31, 2013, 04:03:46 PM »
Try HPC, Chesterfield or Muffett, Tunbridge Wells (I think) or use ordinary spur gears.

Offline Jasonb

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Re: 2:1 Helical gears for Mastiff
« Reply #4 on: May 31, 2013, 04:11:41 PM »
Ian they are crossed helical gears so spurs won't do and Ozzie is in America so better off trying Boston Gear than a UK supplier.

Ozzie are your sizes right as you say both the 8T and 16T are the same overall dia??

Offline JimG

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Re: 2:1 Helical gears for Mastiff
« Reply #5 on: May 31, 2013, 04:33:58 PM »
Try HPC, Chesterfield or Muffett, Tunbridge Wells (I think) or use ordinary spur gears.

HPC's smallest size in 32DP is 9T.  Muffett don't show any details of helical gearing - possibly bespoke.  :(

Jim.

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #6 on: May 31, 2013, 05:29:02 PM »
Thanks Jason, Sent an e-mail to Hemingway. Yes the sizes are correct.

  Check out this site. It explains it better than I can.

http://modelenginenews.org/ed.2003.12.html#t7
 

  Thanks for the reply Jim sent an e-mail there also.

 
  Thanks Ian, Jason's right they are crossed Helical gears.

  Jim I already tried HPC. will try the others. Thanks
 





Offline Jasonb

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Re: 2:1 Helical gears for Mastiff
« Reply #7 on: May 31, 2013, 06:09:22 PM »
Ah yes, different angles on the two gears in which case very unlikely tobe off the shelf from the mainstream gear suppliers.

J

Offline Alankiff

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Re: 2:1 Helical gears for Mastiff
« Reply #8 on: June 02, 2013, 08:02:37 PM »
Hi,
I'm the bloke who bought everything that was left at Bonds when it shut!
Following your post I've dug through the stock room, which is full of gears of all cuts, pitches and materials.

Unfortunately I can't find any of these anywhere. :shrug:

Bonds part number c185 would indeed have been the item you are looking for. The original part number was 5/84.  I have found reference to the gear set in a 1964 Bonds catalogue but it doesn't appear in anything past 1980.

I also have a large number of  Bonds production drawings.  They produced their own gears until about 1975 when they moved from London to Midhurst and outsourced production. Since I don't have the drawings, I cannot even get a set of these cut (one off would be quite expensive but can be done). 

What I can confirm is:
2:1 ratio.
Steel
Both gears have .562 pitch diameter
32DP
1/4 " bore
16 tooth cut 27º
8 tooth cut 63º


I suspect you need to contact Hemmingway who may have stock or may at least have the production drawings.

I Have loads of other 32dp spiral cuts but as the PCDs are all different you would have to make huge design modifications to get them to fit.

Best of luck sourcing a suitable alternative.

Al

Offline MuellerNick

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Re: 2:1 Helical gears for Mastiff
« Reply #9 on: June 02, 2013, 08:46:09 PM »
How much is such a set of skew gears?
I think I could cut them. But just a single set for $10 would be a total loss for me.


And I'd have to buy an imperial reamer. OMG!  :Mad:


Nick

Offline steamer

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Re: 2:1 Helical gears for Mastiff
« Reply #10 on: June 02, 2013, 09:38:26 PM »
Ron,

Check your email...

Dave
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Damned ijjit!

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #11 on: June 02, 2013, 10:19:22 PM »

  Thanks for checking Al. I do have an e-mail sent to Hemmingway but as its a weekend I haven't heard back from them.  Received your e-mail and replied before I read the new posts here.  I was able to figure out the 63 and 27 degrees with help from Marv Klotz's helixcf.exe program. Thanks Marv.

 Thanks for the thought Nick. I understand. A one off is quite job. As far as the bore if it was under .250 I could drill and ream it. 

   Dave, were you referring to Als' e-mail or did you send one?. If so didn't get it.


 Thank again guys.

 Ron
 
   

Offline cfellows

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Re: 2:1 Helical gears for Mastiff
« Reply #12 on: June 02, 2013, 10:24:42 PM »
I made a fixture for cutting true helical gears on my lathe.  Attached is a document I put together about it.

Here's videos of me making the gears and the finished gears...

<a href="https://www.youtube.com/watch?v=oSeMX9SZXXY" target="_blank">http://www.youtube.com/watch?v=oSeMX9SZXXY</a>

<a href="https://www.youtube.com/watch?v=zLZo0ggLoHI" target="_blank">http://www.youtube.com/watch?v=zLZo0ggLoHI</a>

<a href="https://www.youtube.com/watch?v=kAG808sAQ90" target="_blank">http://www.youtube.com/watch?v=kAG808sAQ90</a>

Chuck
So many projects, so little time...

Offline pgp001

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Re: 2:1 Helical gears for Mastiff
« Reply #13 on: June 02, 2013, 11:29:42 PM »
Hi Chuck

That looks to be a very interesting set up, did you say you had a document attached, I can only see the videos.
I would be very keen to see how you have done that.

Phil

Offline John S

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Re: 2:1 Helical gears for Mastiff
« Reply #14 on: June 02, 2013, 11:47:29 PM »
If you have a 1/32" end mill, a copy of Gearotic and a CNC mill it's a doddle.  :stickpoke:



Took al of 5 minutes to do this using Al's information
John Stevenson, Nottingham , England

Offline mklotz

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Re: 2:1 Helical gears for Mastiff
« Reply #15 on: June 02, 2013, 11:58:52 PM »

... I was able to figure out the 63 and 27 degrees with help from Marv Klotz's helixcf.exe program. Thanks Marv. ...

While it's true that I coded the equations and constructed the program, the real credit here goes to Chuck Fellows, a good member of this forum, who did all the math and supplied me with the material to code.

Just want to be sure that credit goes to the right place.
Regards, Marv
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Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #16 on: June 03, 2013, 12:30:45 AM »

  Hi Chuck, I have the plans you posted on the HMEM a couple years back and have been checking them over.

 But for the life of me I could not wrap my head around how 8  teeth meshed with 16.

 Now that John posted his CAD drawing now it all makes sense. Thank you John. :ThumbsUp: :ThumbsUp: Sorry no CNC.

   Your right Marv, I should have mentioned Chuck in that too as I know that you did develop the program after he made his helical gear fixture to help those of us that are a bit math challenged. :embarassed: :embarassed: :embarassed: Sorry for the slip up

  Now I may grind up a form tool to try to cut some or maybe better buy a 32 DP cutter been wanting one any way. Would I need the one that cuts 16 teeth?

   Ron

Offline cfellows

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Re: 2:1 Helical gears for Mastiff
« Reply #17 on: June 03, 2013, 04:09:38 AM »
Sorry guys, here's the attachment...

Chuck
So many projects, so little time...

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #18 on: June 03, 2013, 08:42:26 PM »
I talked to to Hugh in New York, forum name “bytewise”, as he is building a Doxford opposed engine

       http://www.modelenginemaker.com/index.php/topic,1556.msg23103.html#msg23103
   

  He had to cut some helical gears with same angles as the ones I need. Anyway he told me that there was a formula in Machinery Handbook to figure which gear cutters to use cut the gears.  He said you can't go by the ones to cut spur gears.

  I looked up Helical gears in my Machinerys' Handbook 28th Editon Large Print on page 2109. It stated that “the cutter for milling the helical gears is not selected with reference to yhe actual number of teeth in the gear,as in spur grearing, but ratherwith reference to a calculated Number N'  that takes into account the effect on the tooth profile of lead angle, normal diametrical pitch, and cutter diameter.”

It gave a formula of    N' = NK + QK'


K,K' and Q are constants found on pg 2110 in my book.

 After much head scratching and moaning  :headscratch: :headscratch: :insane: :insane: :insane:I was able to figure out how to work the formula.

Math and I go together like oil and water!

N is number of teeth and  K and K' are constants from the table on helix angles and Q is from the table  on Outside and Pitch Dia. Of Standard Involute milling Cutters. On the same pg.

 Any way here is what I came up with. 

  For the 63* gear the formula is:

 N' = (8 x 10.687 ) + ( 53.76 x 3.852 ) = 85.50 + 207.08 = 292.58 say 293    which is a # 1 cutter.

  ( I round up or down to get to 2 decimal points in the totals)

 For the 27* gear it is:

 N' = ( 16 x 1.414 ) + ( 53.76 x .260 ) = 22.62 + 13.98 = 36.6 say 37 which is a # 3 cutter.

  These are for 32 DP cutters.

 Could some one check my math and see if I did it right?

  It looks like I'm going to need to buy some cutters. Hopefully I can sell a couple of never used Gas Model Airplane Engines for large scale models I have and will probably never use, to raise the funds for the cutters.

  Still haven't heard from Hemmingway yet.

  George, did you go thru all this to select the right cutters?

  Ron

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #19 on: June 04, 2013, 01:23:44 PM »
Still no response back from Hemmingway. I'll give it another day and send another e-mail.

Ron

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #20 on: June 07, 2013, 12:26:29 AM »
Got a reply from Hemmingway today.

 They have the gears for 47.50 GB Pounds and 4.70 GB Pounds shipping. Works out to about $ 83.00.

 I can buy the gear cutters for about the same price with shipping, so I guess that is what I will be doing.
 I have been working on the fixture that Chuck developed and hope to order the cutters soon.

  I guess no one wants to check my math.  :headscratch: Oh well.

  Ron

Offline Bezalel

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Re: 2:1 Helical gears for Mastiff
« Reply #21 on: June 07, 2013, 02:02:06 AM »
Hay Ozzie
 
I can't blame you wanting a second opinion on the maths.....  at 83 bucks a shot you (I) couldn't afford to get that wrong too many times.
 
I guess no one out there has amature indemnity insurance for providing amature advice.   :facepalm:
 
Bez
Queensland - wet one day, humid the next

Offline Don1966

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Re: 2:1 Helical gears for Mastiff
« Reply #22 on: June 07, 2013, 02:41:24 AM »
Hay Ozzie
 
I can't blame you wanting a second opinion on the maths.....  at 83 bucks a shot you (I) couldn't afford to get that wrong too many times.
 
I guess no one out there has amature indemnity insurance for providing amature advice.   :facepalm:
 
Bez
Bez this is Ron's thread so let's be discrete. I don't have the indemnity insurance but what kind of advice are you looking for? I can PM you about it.

Don

Offline Bezalel

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Re: 2:1 Helical gears for Mastiff
« Reply #23 on: June 07, 2013, 09:59:13 AM »
Oops  sorry!!
 
Ozzie
 
I can't comment on the formula but for your maths... my spreadsheet gets the same numbers as you.. so its either right or we are both using the same dodgy spreadsheet application.   :Jester:
 
Apologies for my style of humour - Apparently it can get better if you wet it down  :DrinkPint: :DrinkPint: :DrinkPint: .......a lot.
 
 :cheers:
Cheers
 
 
 
 
 
Queensland - wet one day, humid the next

Online Jo

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Re: 2:1 Helical gears for Mastiff
« Reply #24 on: June 07, 2013, 10:12:32 AM »
Got a reply from Hemmingway today.

 They have the gears for 47.50 GB Pounds and 4.70 GB Pounds shipping. Works out to about $ 83.00.

For such a difficult set of gears to cut I would have been tempted to pay my money and know they were good  :shrug:.

Jo
Enjoyment is more important than achievement.

Offline bytewise

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Re: 2:1 Helical gears for Mastiff
« Reply #25 on: June 07, 2013, 01:45:28 PM »
I agree with Jo. If your time is worth anything, it would be best to buy them.
Hugh

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #26 on: June 07, 2013, 02:04:52 PM »


   Thanks for the math check Bez. As far as the humor, no worries.

  Thanks for looking in Jo, Hugh.

  I have WAY more time than money  :lolb: :lolb: so if it takes a few times to get it right that's okay. At least I'll have advanced my machining scope, hopefully.

  Ron

Online Jo

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Re: 2:1 Helical gears for Mastiff
« Reply #27 on: June 07, 2013, 02:07:25 PM »
We will be watching and hoping it goes right  :)

Jo
Enjoyment is more important than achievement.

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #28 on: June 07, 2013, 02:55:35 PM »
Hay Ozzie
 
I can't blame you wanting a second opinion on the maths.....  at 83 bucks a shot you (I) couldn't afford to get that wrong too many times.
 
I guess no one out there has amature indemnity insurance for providing amature advice.   :facepalm:
 
Bez
Bez this is Ron's thread so let's be discrete. I don't have the indemnity insurance but what kind of advice are you looking for? I can PM you about it.

Don

  Thanks for looking in Don. No problem. Nothing here to get upset over.

  Ron

Offline ozzie46

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Re: 2:1 Helical gears for Mastiff
« Reply #29 on: June 07, 2013, 03:04:06 PM »


  Jo, ordered the cutters today. They should be here in a few days.  I will start a new thread when they arrive and I start on my Helical Gear Making journey.

  I made the timing gears and they weren't as bad as I thought they would be. So maybe these won't be either. I have a Grizzly g0704 mill that the head rotates from 0* to 90* on so that should go a long way to easing the pain.

  Ron

 

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