Author Topic: Chris' Build of a Lombard Hauler Engine  (Read 295265 times)

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #885 on: March 03, 2017, 10:35:00 PM »
Thanks guys! It will be a couple days before I get much done on the bevel gears, bunch of other stuff this weekend, including our monthly rc boat/sub run at the local pool. In the meantime, eat cookies among yourselves...!  :cheers:

Online Kim

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #886 on: March 04, 2017, 05:42:50 AM »
Beautiful gears Chris!  You make it look too easy.  :popcorn:
Kim

Offline Don1966

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #887 on: March 04, 2017, 03:34:09 PM »
I just got to find out what you been putting in those cookies Chris..... :lolb: got to be some good stuff Dog because you just don't stop and come up for air.... :lolb: you putting this old Coonass to shame Dog, damn that's some awesome work........ :praise2:

Don

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #888 on: March 04, 2017, 05:58:55 PM »
I just got to find out what you been putting in those cookies Chris..... :lolb: got to be some good stuff Dog because you just don't stop and come up for air.... :lolb: you putting this old Coonass to shame Dog, damn that's some awesome work........ :praise2:

Don
There is something magic about the combination of mint and dark chocolate!   :thinking:

Offline Jo

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #889 on: March 04, 2017, 06:23:27 PM »
There is something magic about the combination of mint and dark chocolate!   :thinking:

And good red wine and castings  ::)

Jo
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Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #890 on: March 04, 2017, 07:36:02 PM »
There is something magic about the combination of mint and dark chocolate!   :thinking:

And good red wine and castings  ::)

Jo
Well, that goes without saying!

Online Flyboy Jim

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #891 on: March 04, 2017, 07:38:18 PM »
There is something magic about the combination of mint and dark chocolate!   :thinking:

And good red wine and castings  ::)

Jo

And even good red wine without castings.  :wine1:

Jim
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"You can do small things on big machines, but you can do small things on small machines".

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #892 on: March 04, 2017, 09:18:58 PM »
Before cutting any metal on the bevel gears, I needed to go through and run the math on the gears. I started with the Ivan Law book, but kept running into incomplete or confusing formulas, so I went and found an online calculator to clarify things. Here is the math I wound up with (spreadsheets are VERY handy things)

 
Number Teeth - N
24
60
Module
0.7
0.7
DP
36.28571429
36.28571429
Pitch Diameter: D= N/P
0.661417323
1.653543307
Diametral Pitch: P= N/D
36.28571429
36.28571429
Whole Depth:  Ht= 2.188/P+.002
0.062299213
0.062299213
Addendum: a= 1/P
0.027559055
0.027559055
Dedendum : b= Ht-a
0.034740157
0.034740157
Clearance: c= Ht-2*a
0.007181102
0.007181102
Circular Tooth Thickness: T= PI/(2*P)
0.043289663
0.043289663
Pitch Angle:  Lp = atan(Np/Ng),  and Lg= atan(Ng/Np)
21.80140949
68.19859051
Pitch Cone Radius:  Rcp= D/(2*sin(Lp)), and Rcg= D/(2*sin(Lg))
0.890460322
0.890460322
Face Width:  F= min(C/3, 8/P)
0.220472441
0.220472441
Outside Diameter:  Dop= Dp+2*a*cos(Lp),  and Dog= Dg+2*a*cos(Lg)
0.712593203
1.674013659
Back Cone Angle:  = 90-L;
68.19859051
21.80140949
Back Cone Radius:  Rbp= Dp/cos(Lp), and Rbg= Dg/cos(Lg)
0.356184129
2.226150806
Virtual Number of Teeth:  Vp= N/cos(Lp),  and Vg= N/cos(Lg)
25.84879107
161.5549442
Offset for second cut on teeth:
0.021629381
0.021642359
Degrees per whole tooth to move rotary table
15
6
Blank Roll - angle to move rotary table for second cut
3.75
1.5
Tooth Depth to cut
0.059444882
0.059444882

Assuming that I did the math correctly (it matched the online calculator so it should), I now have the info I need for cutting the gears (and some I don't, but it was there in the calculator). The numbers really needed are marked in bold. The virtual number of teeth is the number used to pick which cutter to use when cut constant depth bevel gears.
So, time to go pick some bar stock and figure out the setup on the rotary table - need to angle it 21.8 degrees from the centerline of the mill table. Also need to get out the compound slide on the lathe to prepare the blanks, again 21.8 degrees for the four small gears, 68.198 degrees for the two large gears.


Offline Jo

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #893 on: March 05, 2017, 08:51:27 AM »
 :thinking: Chris I think you need to drop a couple of those decimal places, it would make that lot easier to read.

I'm assuming you are talking 68.2 degrees (68.198) because you are cutting on a rotary table rather than an indexing head. I can recommend indexing heads for cutting gears: they have more bearing surface supporting the spindle than using a rotary table in the vertical mode ::)

Do you not have a copy of ShopCalc? Do you really mean 0.7 DP in your calculations?

Jo
« Last Edit: March 05, 2017, 01:06:22 PM by Jo »
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Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #894 on: March 05, 2017, 12:39:36 PM »
Sorry Jo, I had just copy/pasted from the spreadsheet, which had a bushel of decimal places! 


I don't have Shopcalc, what is it?


And it is .7 module, which is 36.2 dp. That is in there correctly if you follow the line across. I have cutter sets for .7 and 1 module gear teeth, were bought for clock projects originally.


I got the blank set up for the first gear last night, and the rotary table angled over, pics later today.

Offline Jo

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #895 on: March 05, 2017, 01:05:32 PM »
0.7 module was what I thought.... Corrected sheets attached.

Shopcalc: http://home.scarlet.be/mini-draaien-frezen/engels/program-01.html a useful little calculator program that I use to quickly do the maths for gear cutting  ;)

Jo
Usus est optimum magister

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #896 on: March 05, 2017, 01:11:44 PM »
Looks like a great utility, I'll give it a try! Thanks!

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #897 on: March 05, 2017, 05:08:57 PM »
Okay, I got the boat stuff ready for the pool run later, so on to the first bevel gear. I am starting with the four smaller gears - less stock to waste in case of boo boo's, which I already had one of when I forgot to reset the Z axis on the third pass.

To start, chucked up a length of brass bar, and turned the end down to the outside diameter of the gear.

Then, turned in the hub at the end, and used the compound rest to turn in the bevel where the teeth will go, at 21.8 degrees.

Then over to the mill, with the chuck held on the rotary table just like was done for the spur gears earlier. The one difference is that the rotary table needed to be turned 21.8 degrees to put the bevel on the gear in line with the mill table. Not having a good way to measure that angle, I held a straight edge on the side of the gear blank, and sighted down to the mill table and adjusted till it lined up. Then I drilled another hole in the table extension for another hold down bolt, and put on a clamp at the front for good measure.

After carefully centering the cutter on the end of the blank (used the tool marks on the end of the blank to know where the middle was), the table was moved in till the cutter just touched the blank, then in again by the depth of the teeth. Then, the first pass was made as with a normal spur gear, 15 degrees per tooth for the 24 tooth gear.

Then comes the interesting bit with bevel gears. If you look closely at the teeth after the first pass, you can see that the outside ends of the teeth are wider than the gap between the teeth. The next two passes will fix that. For the second pass, the cutter was lowered by 0.021" from the center position, and the rotary table starting position moved clockwise by 3.75 degrees (which is 1/4 of the 15 degree full tooth). At this new position, the cutter enters the opening in the narrow end of the blank that was cut on the first pass, but as it moves along it takes more material off one side of the tooth, narrowing it at the outer end. A pass on all the teeth was made, turning the rotary table 15 degrees from the new starting point for each tooth.

Then, for the third pass, the cutter was raised back to the starting point, and another 0.021" up past the starting point. The rotary table starting position was moved counterclockwise by 3.75 degrees, which puts the cutter at the center of the narrow end opening again, but takes a little off the other side of the tooth.

It can be hard to see the difference looking between the three photos, so here is a montage of all three:

It is still a subtle difference from pass one (left) to two (middle), but if you compare one to three, it is clear that the outer ends of the teeth are narrower, matching the center gap. At least it should. Hard to be sure with just one gear made, the real test is when the matching large gears are made later, I will make all four small ones with the current setup, and hope it is right.
The next step on the first gear was to drill for its axle,

and part it off to size:

Here is the first one test fit in the differential plate:

All spins freely, so next time I'll make the other three small gears...
« Last Edit: June 04, 2018, 01:37:46 AM by crueby »

Offline crueby

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #898 on: March 05, 2017, 07:07:08 PM »
Gear number 2 made, 2 to go.

Good news on it is, it meshes nicely with the first one, though not at 90 degrees naturally. Still, a good sign that the shapes are right, will know for sure when the 60 tooth ones are made...
« Last Edit: June 04, 2018, 01:37:54 AM by crueby »

Online Kim

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Re: Chris' Build of a Lombard Hauler Engine
« Reply #899 on: March 06, 2017, 03:38:15 AM »
That is pretty cool, Chris!  I really appreciate the step by step on the bevel gears, and the 3 pass picture. That is very interesting.  Now I'm going to have to make some bevel gears some day.  You make it look so easy!

Can't wait to see the mating part of the differential!
Kim