Author Topic: Tangler's Air Cooled Farm Boy  (Read 3381 times)

Online Jasonb

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Re: Tangler's Air Cooled Farm Boy
« Reply #30 on: August 07, 2019, 04:07:56 PM »
All the hit and miss engines I have made have had both gears in steel so can't see that as a problem.

Those are quite fine teeth you could probably come upto 24DP or 1MOD quite easily if you have the cutters.

Offline tangler

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Re: Tangler's Air Cooled Farm Boy
« Reply #31 on: August 08, 2019, 11:50:02 AM »
I've got a set of 0.8MOD cutters.  48T has a PCD of 38.4mm and 24T half that at 19.2.  Seems like a better option,  I'll be adjusting the position of the crankshaft gear to fit anyway.

Cheers,

Rod

Offline tangler

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Re: Tangler's Air Cooled Farm Boy
« Reply #32 on: August 09, 2019, 04:40:52 PM »
The first job with the gears was to slice off a piece of Free Cutting mild steel



I faced this and then drilled and reamed as before 3/8"



The blank was then fastened on to a mandrel and turned to the required OD for the gear.  When I can I like to make my mandrels from Precision Ground Mild Steel so I can keep them and then re-mount in a collet for accuracy.



Getting the centre of the gear cutter is tricky since, in my experience, the cutting teeth are not necessarily in the centre of the tool.  Eyeballing seems to be the best method but care has to be taken to avoid parallax error as seen in the photo where the camera was not truly in line with the cutter.



On my dividing head, 48 divisions is 1 and 1/4 turns - 1 turn and 15 holes on the 60 hole plate



Each tooth was cut to the full depth in one pass.  Always a relief when the final tooth is at the correct spacing



Rinse and repeat for the 24 T gear, 2 1/2 turns for each tooth.



The gears were finished to thickness in soft jaws trimmed to size



The smaller gear has a boss for a set screw.  I'm going to have to make some new heaxagons for the jaws soon.



I drilled the hole for a M3 grub screw using my tool post milling attachment which is set on centre height



Here's the pair of finished gears.



The plan is to make all the stuff that goes in-board of the flywheel on the governor side so that I can make sure that the spacing is correct before I cut the keyways in the crankshaft.

Cheers for now,

Rod


Offline Admiral_dk

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Re: Tangler's Air Cooled Farm Boy
« Reply #33 on: August 09, 2019, 08:08:35 PM »
Those gears came out great  :ThumbsUp:    :cheers:

Offline Roger B

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Re: Tangler's Air Cooled Farm Boy
« Reply #34 on: August 10, 2019, 05:36:10 PM »
Excellent gears  :praise2:  :praise2:  :wine1: Something I need to try one day (along with CNC and … and …)  ::)
Best regards

Roger

Offline bruedney

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Re: Tangler's Air Cooled Farm Boy
« Reply #35 on: August 10, 2019, 09:02:39 PM »
I've got a set of 0.8MOD cutters.  48T has a PCD of 38.4mm and 24T half that at 19.2.  Seems like a better option,  I'll be adjusting the position of the crankshaft gear to fit anyway.

Cheers,

Rod

Hi Rod
I am just setting out on a water cooled journey and am going to metricise the build and have been wondering about the same issues. You say above you are going to adjust the position of the crankshaft gear. Does that mean you are going to move the crankshaft & bearings? I would have thought the big gear would be the easier one to move.

Watching with interest

Bruce
‘Results! Why man, I have gotten a lot of results. I know several thousand things that won’t work.’ — Thomas Alva Edison

Offline tangler

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Re: Tangler's Air Cooled Farm Boy
« Reply #36 on: August 10, 2019, 09:29:21 PM »
Hi Bruce,

No, that was clumsy phrasing on my part.  I'll adjust the position of the cam shaft so that the  2 gears mesh correctly.  In your metric version I guess you could go to even coarser gears as Jason suggests.  I wonder why Jerry chose such fine gears although it does provide the ability to have finer adjustment of the timing.

Cheers,

Rod

Offline bruedney

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Re: Tangler's Air Cooled Farm Boy
« Reply #37 on: August 11, 2019, 01:53:07 AM »
Thanks for the clarification

Bruce
‘Results! Why man, I have gotten a lot of results. I know several thousand things that won’t work.’ — Thomas Alva Edison

Online Jasonb

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Re: Tangler's Air Cooled Farm Boy
« Reply #38 on: August 11, 2019, 07:30:51 AM »
I wonder why Jerry chose such fine gears

Probably had the cutters to hand.

Looking at your finished gears I would say that tooth size looks about right though 1MOD would not be a lot larger and easy to buy complete gears cheaply if you don't want to cut them.

I've also just done some 0.8MOD size ones. 21T & 42T


Offline b.lindsey

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Re: Tangler's Air Cooled Farm Boy
« Reply #39 on: August 11, 2019, 12:43:38 PM »
Fine looking gears and a nice family shot too Rod. Still following along with your build.

Bill

Offline tangler

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Re: Tangler's Air Cooled Farm Boy
« Reply #40 on: August 14, 2019, 08:24:50 PM »
The cam is a simple 2 radii job.  The OD was turned to the diameter of base circle plus lift, then I mounted the blank on a mandrel in the dividing head a milled across the base circle at 3degree intervals (that's half a turn on the DH)



I like to say a little mantra to myself on these types of jobs:

Turn  (rotate the dividing head to the next hole)
Sector  (move the sector arms ready for the next turn)
Cut  (move the job under the cutter)
Mark (cross off the cut on the list)



I used a dead smooth (#6 cut) file to get rid of the machining marks and parted off the finished cam



The spool is the bit that slides along the crankshaft to actuate the miss mechanism, driven by the governor's balls.  This a simple turning job but it needs a pair of slots on either side for the governor arms.  Again, I mounted it on the 3/8" mandrel in the dividing head and used a little 1/8" FC3 cutter after carefully lining everything up and zeroing the centre of the cut on the DRO.  Then rotated through 180 degrees and repeated



This all went very well.  Since I changed the drive belt on the mill to poly V it runs very smoothly and quietly at 2800rpm





That's all for the moment.


Online Jasonb

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Re: Tangler's Air Cooled Farm Boy
« Reply #41 on: August 14, 2019, 08:31:28 PM »
Rod, on a job like that does it really need the sectors moving? I tend to do as you said and simply do half a turn or one turn of the handwheel etc, 10mins either way won't make a lot of difference. At the most plate with two opposite holes marked with a sharpie will be Ok.

Offline tangler

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Re: Tangler's Air Cooled Farm Boy
« Reply #42 on: August 20, 2019, 10:00:42 PM »
This job is the governor weight fulcrums and hub.  The fulcrums were first roughed out (very!).  The important spacing is the distance between the fulcrum holes and their height from the base.  By using a pair of filing buttons of 1/4"OD in the holes that pretty well defines the shape, the arms just need to be mounted at the correct angle in the vice before milling across, using the buttons to get the thickness.  The pair were sandwiched together with 8BA screws.







The hub is also brass.  Jerry calls for the OD to be 1.045" but I've only got 1" so that will have to do.  My problem here is that I will need to hold the hub in something in order to mill the slots for the arms.  I decided on an ER25 collet block so turned a stub to 15mm diameter to fit in a collet



With the collet in the lathe I turned the hub to final thickness and then put a tiny centre in so I can find it in the mill



I've never actually used this pointed "edge finder" before and am not sure how they are supposed to be used but a finger seemed to work to determine whether the parts were concentric



So, with the DRO zeroed on centre I could cut the 2 x 1/8" slots



The holes in the arms were opened out to 3/32" with a reamer



A couple of lengths of 3/32" rod kept the arms aligned and they were anointed with soft solder paste and then warmed up with a torch until the solder flowed.  I had to ease the slots slightly with a file to give the solder some working room.



The problem now was that I need to bore a 0.602" hole and the spigot is only 0.591.  Fortunately, the jaws of my little 4" 4jaw (just) fit between the arms.  I hadn't thought that through, I was just lucky  :-[



Here it is, pretty much finished but I'll probably do a little more filing to tidy things up.



This is my rather Heath Robinson set up for ball turning.  The dividing head has a choice of seats.  It was manufactured on the Myford so the bore in this configuration is automatically on centre height.  On the other face the centre height is greater and allows a 4" chuck to be used on the mill.  The tool holder was made from an orphaned Flexispeed top (compound) slide riveted to a N0.2 Morse Taper.







A pair of Governer's Balls.



Cheers,
Rod

Offline Brian Rupnow

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Re: Tangler's Air Cooled Farm Boy
« Reply #43 on: August 21, 2019, 12:12:11 AM »
Tangler--You are doing nice work. when I get into assemblies that are as small as you show, I generally make a "one time use" jig to hold everything in position for soldering, then the jig is cut away.---Brian

Online Jasonb

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Re: Tangler's Air Cooled Farm Boy
« Reply #44 on: August 21, 2019, 08:13:40 AM »
You are making good progress on this one now Rod, your ball turner leaves a nice slim attachment point.

Your post about the cam got me thinking about the ones I need for the present engine so I put them into F360's CAM and hopefully later today will post in the Darkside thread that it cut each cam in just over 2mins.