Farm Boy hit or miss ( pic intensive )

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GlennW
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Location: Florida

Re: Farm Boy hit or miss ( pic intensive )

Post by GlennW »

Possibly no mandrel or tailstock.

If it's a horizontal/vertical RT, set it up vertical with a piece of round bar. Mill the OD to size and mill the bore to size using the RT, flip it up horizontal and mill the teeth. Everything will be concentric. Remove the shaft take it over to the lathe and part off the gear.

Or, set up a bar in the RT with it vertical and machine a 3/8 boss on the end using the RT, drill and tap it for a 1/4" bolt and you have a mandrel that will be concentric with the table axis as long as it is not removed.

For either method, just don't stick the bar out any farther than is needed for spindle clearance.
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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coal miner
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Location: Southern Illinios

Re: Farm Boy hit or miss ( pic intensive )

Post by coal miner »

Glen , thanks for your response . I'm assuming you are mounting the bar in a chuck on the RT ? Don't have one for the RT , yet . Some thing else to buy $$ , does it ever end ? . So all I have to work with are the dead centers . Made a mandrel yesterday , that will fit the two gears , being they are both the same diam . .375 i.d. Couldn't figure an expanding type , so made it w/ a locking nut and over size washers to secure the blank . Haven't mounted the RT yet to see what the run out will be , hopefully today . Cut the blanks to size , probably should have left them a little over size and milled to the finished o.d. I see what you are saying tho about keeping the ops to the RT to finishing in regards to concentricity . The gear material is to be phosphor bronze (72T) and steel (36T) and depth of cut according to print .045" , maybe deflection won't be a problem . Will dial everything in and see how it goes , probably won't be close . I will make the cuts in small steps if everything checks out . May be back to the drawing board if this set up doesn't work and pop for that 4-jaw chuck for the RT .
The more I learn , The more I don't know !
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GlennW
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Re: Farm Boy hit or miss ( pic intensive )

Post by GlennW »

Not having a chuck on the RT does change the plan!

If your mandrel was made between centers you should be good to go as far as run out, unless the spindle bore in the RT is not concentric with it's axis.

Keep in mind that there can be no slop in the drive dog anywhere or your teeth will be erratically spaced.

For .045" infeed I'd cut the teeth in one pass if possible. Additional passes just give you more opportunity to mis index and mess up a tooth!



You have done some great work here, so I probably don't need to even post this stuff, just thinking out loud!

Have fun!!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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GlennW
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Joined: Sun Apr 15, 2007 9:23 am
Location: Florida

Re: Farm Boy hit or miss ( pic intensive )

Post by GlennW »

Not having a chuck on the RT does change the plan!

If your mandrel was made between centers you should be good to go as far as run out, unless the spindle bore in the RT is not concentric with it's axis.

Keep in mind that there can be no slop in the drive dog anywhere or your teeth will be erratically spaced.

For .045" infeed I'd cut the teeth in one pass if possible. Additional passes just give you more opportunity to mis index and mess up a tooth!



You have done some great work here, so I probably don't need to even post this stuff, just thinking out loud!

Have fun!!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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coal miner
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Location: Southern Illinios

Re: Farm Boy hit or miss

Post by coal miner »

Cut my first gear ! Thanks for the guidance Glen . 72 tooth , 48DP , 1.542" o.d. ,and .045" depth of cut. The first thing to make after receiving the cutters from McMaster-Carr was to make a mandrel to mount the cutter . Had some 1" 12l14 turned to 3/4" shank and .875" stub to accept the cutter . Polished a 1/2 thou off on the stub end so the cutter would be tight , 1/8 " key and machined washer w/ a 5/16" SHCS to hold it in place .

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In the conversation w/ Glen got some ideas for holding the gear blank . Decided to make an arbor for the 3/8' hole in the blank and machined some washers and threaded to tighten up on the blank and hoped like the devil it wouldn't move . Put a center in the RT and used the center in the tail stock to support things . Used a close fit drive dog to turn everything . Adjusted the horizontal , then checked the runout on the gear blank and ended up .002" . One thing I did on the arbor was to machine a flat on the dog end for the lock screw to seat on . Got to buy a chuck for the RT !

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Set the rpms to 370 for the brass and proceeded to turn the crank , every 5 º and make a cut , 72 teeth . Once around came back to start , the first tooth cut didn't even make a sound . went to the second recut and same thing . Guess that says something about the accuracy of the Phase II RT .

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Cut from right to left w/ the motor running reverse so the thrust would be against the RT . Don't know if this would be a problem , but the RT is bigger than the tailstock so should be more solid , also pushing against the machined larger shoulder in the arbor .

Pretty happy with the out come , under magnification you can see a definite tooth profile . Of course have another small 36T to make and then see if they run together ok .
That's a piece of 1/8" key stock on the right side of the gear to get a sense of size

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Got the governor assembly done this week also , so it's been a good week and no scrap .....Yet .

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One thing that helped is sunshine and 60º temps . Maybe ole man winter is finally giving up !
The more I learn , The more I don't know !
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GlennW
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Re: Farm Boy hit or miss ( pic intensive )

Post by GlennW »

Looks like another great day running the machines!

Great work!!
Glenn

Operating machines is perfectly safe......until you forget how dangerous it really is!
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coal miner
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Re: Farm Boy hit or miss ( pic intensive )

Post by coal miner »

Pretty well have the head assem. done . The mixing valve was an experience in in close tolerances . The spray bar .125" that the 2-56 needle screw goes in has a .020" hole thru it that is the fuel adjustment for the engine . The plans called for a PM Research ell , didn't want to wait on one so just measured everything out and made the one shown . Hope it works . All parts are held w/ 4-40 set screws .

The valve springs were made on a mandrel w/ the threads cut to hold the spacing of the coils . .029" w/ 6 turns exhaust and .019" for 7 turns for the intake . Had to play with the diam. a little to get the right spring diam . because once released the coil expands . Plan on heat treating these to preserve the springiness . (sp)

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I've been using the modified ER-40 chuck in the lathe quite a bit , sure makes it easy to swap back and forth to a 5C block to mill the flats and the hexes . Kinda of neat on the spring making so made another to tension the needle screw .After polishing everything up , a little bitty knurl set things off .

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Got a few more parts to make , one of them the delrin holder for the Hall Effect ignition . The biggest one tho , is makin the taper lock bushings and then the biggy of boring the fly wheels to match . Sure don't want to mess this operation up , awful lot of time in those flywheels . Will do some scrap parts to make sure of the fits first !
The more I learn , The more I don't know !
Nudge
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Re: Farm Boy hit or miss ( pic intensive )

Post by Nudge »

Have you got this engine finished yet?
Looks real nice :D

What spark plug do you use for it?
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