Ford 300 Inline Six

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mayhugh1

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I wanted to wind down for the Thanksgiving holiday by machining some standalone parts that I could fully complete. The first of these was the alternator. My camera's SD card failed and took the alternator's construction photos along with it, and so I staged a photo showing its disassembled parts. The aluminum housing was bead blasted to simulate the surface finish on the full-size casting. The armature spins in a set of inner/outer ball bearings. Its cooling fins were Alodine'd to simulate a period cad-plated finish. The steel mounting brackets turned out to be the trickiest pieces to machine. I thought I had finished the head long ago, but one last drilled/tapped hole was needed for the upper bracket. Unfortunately, the alternator's output voltage and current turned out much too low to charge the battery, and so the alternator's only real function will be to tension the fan belt.

Another of these parts was the mechanical fuel pump that I also 'cad plated'. Since I normally run electric fuel pumps on my model engines, its sole function will be a block-off plate.

The last pieces machined before Thanksgiving were a spin-on oil filter and the dip stick and dip stick tube. The filter was Gun Kote'd white to match the Motorcraft filter that was stock on the engine. - Terry

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Sparkplug

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Hi. I've come late to this particular feast, I'm only a few weeks into my build, I have a basic question regarding the two helical gears for the distributor drive, is there a particular reason why they have to be a14 tooth gear? Surely if the gears are 1:1 ratio they could be larger, say 10 teeth as these are readily available.
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gbritnell

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Hi Sparkplug,
The gears have to be that size so they will pass through the cam bores.
 

Sparkplug

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Hi. George.
That wasn't what I was asking, it was the number of teeth, the o/d of the 10 tooth gear is 8mm. So making the bore 8mm rather than 5/16th should be fine and as the ratio is 1:1they should work okay, I was only making sure there wasn't some reason for 14 teeth that I was unaware of.
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Charles Lamont

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The involute tooth profile for gears with few teeth (less than 12, say) gets nasty, with a lot of undercut that weakens the teeth, and, I should think, would make the skew gears tricky to cut. This can sometimes be mitigated by measures such as addendum modification but I don't think that would be applicable in this case. A few more teeth, 14 for example, makes the tooth profile more sensible and makes for a smoother drive. On the other hand, bigger teeth (larger module or smaller DP) are stronger. In a fixed, limited space, the design choices will be a compromise. Do you hold something against 14-toothed gears?
 
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gbritnell

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The outside diameter of the gear is based on the diametral pitch of the gear. The D.P. is 72 so the calculated O.D. is .303. Are you asking if a 10 tooth MOD. gear would work? A 10 tooth, 72 D.P. gear won't work. The cam bore could be changed to M8 (.315) but I don't see how that relates to your gear question.
 

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The involute tooth profile for gears with few teeth (less than 12, say) gets nasty, with a lot of undercut that weakens the teeth, and, I should think, would make the skew gears tricky to cut. This can sometimes be mitigated by measures such as addendum modification but I don't think that would be applicable in this case. A few more teeth, 14 for example, makes the tooth profile more sensible and makes for a smoother drive. On the other hand, bigger teeth (larger module of smaller DP) are stronger. In a fixed, limited space, the design choices will be a compromise. Do you hold something against 14-toothed gears?
I've nothing at all against 14 tooth gears, I'm sure the vast majority lead blameless lives, but as I've only got a very modestly equipped workshop producing them would be nigh on impossible. But I can source two 8mm diameter x 10 tooth 45 degree helical gears from Germany for 16 euros, so all I wanted to find out was the reason that 14 tooth gears were specified
 

mayhugh1

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The stock bore for the cam bearings is .312" which was probably selected so a standard reamer could be used. There's enough excess block material around it so you could increase that to .320" or so (and the cam bearings accordingly) so you could use the commercial gear set you found. So long as the tooth ratio is 1:1 I would think a 10 tooth gear set would work. - Terry
 
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Sparkplug

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The stock bore for the cam bearings is .312" which was probably selected so a standard reamer could be used. There's enough excess block material around it so you could increase that to .320" or so (and the cam bearings accordingly) so you could use the commercial gear set you found. So long as the tooth ratio is 1:1 any number of terth will work. - Terry
Thanks for the vote of confidence Terry, I can't see any reason why it won't work. I suspect few engineers don't have a cnc with a forth axis as I don't know of any other way, except for a dividing head driven by a gear train from the table feed to produce these gears, so have no other choice than to use commercially available gears.
 

mayhugh1

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Thanks for the vote of confidence Terry, I can't see any reason why it won't work. I suspect few engineers don't have a cnc with a forth axis as I don't know of any other way, except for a dividing head driven by a gear train from the table feed to produce these gears, so have no other choice than to use commercially available gears.
CNC isn't actually required. Here's how George did it using a Chuck Fellows fixture:


You can search this forum for Chuck's work. - Terry
 
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Sparkplug

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CNC isn't actually required. Here's how George did it using a Chuck Fellows fixture:


You can search this forum for Chuck's work. - Terry
Ingenious, I take my hat off to people who think out of the box. But, on balance the choice between the time and effort in making the fixture and with no real guarantee that my efforts would be successful versus a set of precision gears for 18 euros, although a tough one, I think I'll go with German gears. But thanks for posting the video, you truly do learn something new every day with this game!
 

Alec Ryals

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CNC isn't actually required. Here's how George did it using a Chuck Fellows fixture:


You can search this forum for Chuck's work. - Terry
Hello,
Were can i find info on this gear cutting fixture
 

gbritnell

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Do a search for helical gear cutting lathe attachment. It will come up under Chuck Fellows posting
 

Basil

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Very impressive! Nice to know I can make a helical gear when the need arises.👍
 

mayhugh1

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Although the crankshaft and block were machined long ago, the main bearings were not. A portion of the block's machining included recesses for seven 7/8" diameter bearings. These were machined using a single g-code routine in hopes of getting them all identical and in a straight line through the center of the crankcase. Ballbearings were installed in the two outside recesses, but the five inner ones have been awaiting two-piece bronze bearings.

Their machining began by turning work-holding spigots on the ends of a pair of SAE660 rounds. Each was sized for five bearing halves plus a spare, and their o.d.'s were turned to what will be the finished diameter of the bearings. One of these blanks, used for the halves that will be mounted inside the recesses, was marked for later return to the lathe in its same orientation.

After careful setup on the mill, half the diameter of each blank was machined away. The two workpieces were then clamped together with hose clamps while the hole pairs for the bearings' mounting bolts were drilled, counterbored, and temporarily tapped. With the workpiece halves joined together with temporary screws, the assembly was returned to the lathe where the through-hole for the bearings' i.d.'s was drilled and reamed.

When the crankshaft was machined, its two outer journals were turned just under .375" for their fits inside the ball bearings. The inner journals, although identical, wound up slightly elliptical with cross-measured diameters of .366"/.367" resulting from unavoidable flex during machining. To compensate for these errors and to provide adequate clearance in the engine's pump-less splash oil system, a .370" reamer was run through the assembly before the bearings were parted from it.

After parting, but before separation, each bearing half was engraved with locator numbers to avoid mix-ups during assembly. In addition, an oil collection slot was machined into each bearing's top half to aid lubrication. After reaming out the threaded holes for mounting bolt clearances, the bearings were installed and test fitted one-by-one.

I'm not a fan of brute-force spinning a tight crankshaft with an external power source until it 'loosens up". Instead, the fitting was done by bluing and scraping each bearing and/or machined recess as needed. This was a tedious process that required some dozen hours and something I'd put off as long as possible.
Rather than begin fitting using the actual crankshaft, I started with a .375" diameter test bar whose diameter between ends had been carefully turned down to .368". This diameter was chosen to arrive at a fit that would hopefully allow the crankshaft to be dropped in with minimal cleanup.

My initial plan was to fit the bronze bearings one-by-one to the test bar with it installed in the ballbearings. However, I discovered four of the five mounted bearings had actually come out as hoped and would require minimal work if the front ballbearing was instead lowered .0015" by scraping its recess. So, I ended up first fitting the five bronze bearings to the bar without the ball bearings and then fitting the front ballbearing to the bar.

With all the scraping/polishing completed, the crankshaft actually did drop in as hoped. When turned by hand without the ballbearings, the .001" errors in all five of the crankshaft's dry egg-shaped journals could be felt as tiny 'bumps' telling me the fits were as good as I could expect. Squirting a drop of oil into the oil collection slots made the bumps all but disappear. Installing the ballbearings totally eliminated them.

I've never found the fitting of a multi-cylinder crankshaft to be satisfying. Regardless of the steps taken to stiffen a long skinny crankshaft during its machining, there's always a bit of flex that leaves circularity errors in its lathe-turned journals. And these errors invariably limit the quality of the bearing fits. It could be argued that unless the journals are ground, some variation of the brute force fitting technique is good enough. I've spent a small fortune on tool post grinders though and still don't have a usable solution for crankshafts running on my lathe. - Terry

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gbritnell

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Very nice Terry! I like what you did with the bearings. I agree with you on the task of machining and fitting crank to bearings. Not my most enviable process!
 
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