Author Topic: Jkson 6/1 rebuild  (Read 134132 times)

George A

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Re: Jkson 6/1 rebuild
« Reply #105 on: February 21, 2015, 05:16:00 PM »
My first thought when I saw the pic was that the holes were intended as drains.......to allow surplus oil back into the crankcase. As 32 coupe mentioned, every stroke of that lifter is going to coat the lifter with splashed oil and lube its bore.

Almost every splash lubrication engine I've ever worked on MIGHT have oil access holes, but on TOP of the fitting. Even with splash, oil doesn't "splash uphill" too easily.
« Last Edit: February 21, 2015, 05:18:39 PM by George A »
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Gippslander

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Re: Jkson 6/1 rebuild
« Reply #106 on: February 22, 2015, 07:52:15 AM »
Ok

re: the holes in the guides . Ok it seems that its not that important which way they go in . I have looked at the lifter faces , the finish on them is pretty good, with a slight convex curve

I found a piece of cast iron for the new bush .

I am a average machinist, taught myself mostly .

I will bore the bush to .870", then after installing the bush in the block, I will use a reamer to get it to .875"

The 1950's PREMO lathe was made here . It had a broken back gear when I got it, and I managed to make a new gear for it

The 3/4" drill in the pic, the chuck is turning slowly with the back gear engaged ..

Mike

« Last Edit: February 22, 2015, 07:55:56 AM by Gippslander »
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Gippslander

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Re: Jkson 6/1 rebuild
« Reply #107 on: February 23, 2015, 11:06:56 AM »
Well, the new end bush has been fitted . The camshaft now has .001" clearance instead of the sloppy .010"

Mike
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Gippslander

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Re: Jkson 6/1 rebuild
« Reply #108 on: February 25, 2015, 08:38:39 AM »
I am wondering if the reason for so many broken idler gears is , the camshaft bushes are worn or as in my case , are badly out of specification .

Mike

PS  just done a test fitting of the idler gear . The gear has a wobble , the shaft diameter  is too small or the hole diameter in the gear is too big  ::)

Also, the idle gear is not meshing with the crank gear as it should , too much backlash . The cam gear side seems to be meshing OK

Looks like I will be making a new shaft . I will have to buy some 4140 grade steel .
« Last Edit: February 25, 2015, 11:56:26 AM by Gippslander »
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38ac

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Re: Jkson 6/1 rebuild
« Reply #109 on: February 25, 2015, 12:34:32 PM »
. I really do not consider myself to be in the same league as some of the guys who laid down the ground work on these engines but I do have the advantage of being  able to look backwards at what they went through and analyzing the thought processes, some good, some flawed. I also have the advantage of being through quite a few of these engines, both the originals and the Indian versions and gear problems are not unique to the Indian engines. That knowledge would have helped some of the guys early on who thought that any gear problems were caused by India.  
Taking everything into consideration, what I can read here in the archives and what I have experienced in my shop has brought me to the opinion that the major factor is backlash, not the gears. I am not the pioneer with that thought but I do subscribe to it. I have seen test run and very low houred engines with "the red gears" "the green gears" and bronze gears all beat to pieces. And in every case the common denominator was improper positioning of the idler which makes for increased backlash. If a person reads all of Georges ramblings on this subject he will see that he knew that the bronze gear was more of a crutch than the fix. If he addressed backlash I don't recall reading it.  In reading through old posts it is readily apparent that most did not fully understand the impact of a little bit of extra gear lash. Just the same as a lot of users did not (and still dont) understand the impact of a "little bit" of sand and slag floating around.
The beating the gears take is GREATLY magnified by a small amount of extra backlash. The difference in gear speeds at the time of impact is tremendous with only a .010 increase in back lash. It would take an engineer to calculate the exact forces involved but they are great. A person just has to get past any thinking that fixing excessive gear lash comes behind worrying about the gear materials.

In my build thread  I summed this all up by saying, inspect the gears, throw out any that are obviously bad and get the lash right. If an engine has been run, even just test run with grossly excessive gear lash the idler gear is junk and sometimes so will the cam gear be junk. A casual look over will not bring this out, look at the gears under a strong light preferably with a magnifier
This is what I have experienced with work through my shop.
« Last Edit: February 25, 2015, 12:37:58 PM by 38ac »
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32 coupe

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Re: Jkson 6/1 rebuild
« Reply #110 on: February 25, 2015, 10:50:04 PM »
Mike,
On your idler gear......I made an offset bushing for mine that took care of the lash problem.
If you look at my earlier posts you will see pics of how I did it.

Gary




Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

Gippslander

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Re: Jkson 6/1 rebuild
« Reply #111 on: February 26, 2015, 01:19:03 AM »
Mike,
On your idler gear......I made an offset bushing for mine that took care of the lash problem.
If you look at my earlier posts you will see pics of how I did it.

Gary






Ok good advice
and thanks 38ac


I measured the bore of the bronze idler gear - .875"    .    The diameter of the shaft is .873" , so I can see where the gear wobble is coming from

Yes , I will make a new shaft with the eccentric section  . That will test out my machining skills  ::)

I havent machined the harder grade ste้l as yet.  the 4 jaw chuck with a 25 thou shim on one of the jaws sounds good

I am fixing up my Harrison lathe with a 2hp motor
that should handle the 4140 steel .
« Last Edit: February 26, 2015, 01:22:22 AM by Gippslander »
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Quinnf

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Re: Jkson 6/1 rebuild
« Reply #112 on: February 26, 2015, 01:24:32 AM »
[snip]  If a person reads all of Georges ramblings on this subject he will see that he knew that the bronze gear was more of a crutch than the fix. If he addressed backlash I don't recall reading it.  

That's right.  Since most gears lost teeth opposite the "00" mark that was stamped into the rim, it was thought that impact stress caused localized deformation, which lead to localized weakening.  Soon, however, it became apparent that manufacturing inconsistencies made some engines loose teeth like a septuagenarian, while others seemingly ran forever.  Joel spent a considerable sum of his own money having the gear profile analyzed, and the recommendation was to try making the idler gear from bronze.  

Dave, (Xyzer) spent some time and measured a block accurately and turned up the fact that the idler gear shaft was mislocated in relation to the crankshaft and cam, and he was the first person to identify the issue of backlash as the likely cause of gear stripping.  I don't recall anyone who installed the offset idler spindles that he made available for a time, having any further problems.  

The Ashwamegh 6/1 that was my first engine, made a terrible "clack" as the engine cranked over each cam lobe without compression.  After making a series of idler spindle bushings drilled offset 0.005 to 0.030", I found that the 0.010 bushing brought the backlash to the point where I couldn't hear the "clack" anymore.  I used thickness gauges to measure the backlash, but because of the cramped quarters and difficulty of seeing into the crankcase, I wasn't very comfortable with the precision of my measurement.  So I chose the bushing that eliminated the "clack."  

For the sake of posterity, I'd like to understand how you measured gear backlash.  I haven't read anyone describe in detail how they actually measured the lash.  

Quinn
« Last Edit: February 26, 2015, 01:27:48 AM by Quinnf »
Ashwamegh 6/1, PowerSolutions 6/1 "Kit" engine, and a Changfa R175a that looks like a Yanmar I once knew

32 coupe

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Re: Jkson 6/1 rebuild
« Reply #113 on: February 26, 2015, 02:02:42 AM »
Quinn,
Good point. I remember reading about using a dial indicator.  I just couldn't see it.
I made a few offset bushings and "played" with them untill I got it to were it "felt" correct.

Most of us "old timers".have worked with machinery, built.engines of one type or another,
built things and blown up and destroyed a few.things along the way.

Experience and hands on time is stil the best teacher in my opinion.

Gary

PS: I turned my offset bushings on my lathe.  I turned the bolt center section to 1/2" then
used 1/2" ID mild steel tube wih 1/8" wall to create offset bushing.
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

38ac

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Re: Jkson 6/1 rebuild
« Reply #114 on: February 26, 2015, 02:38:42 AM »
In going back over my build thread it is apparent now that I breezed by quite a few things that are of importance. This was mostly out of the fear of coming off like a know it all and partly due to the fact i didn't set out to write a novel. In real life I am actually pretty meek but my ramblings don't come off that way sometimes,, that I am certain of and apologize for.

Anyway back to measuring lash. I will take some pictures in a few days but I wanted to answer Quinn's question.
 Doing it with the cylinder removed is a whole 'nother ball game than trying to do it in an assembled engine which is real hard to do. In the shop I have several different styles of indicators and attaching hardware. I start out the with crankshaft installed and the idler gear installed and by positioning the indicator in the hole for the governor cover it is fairly easy to indicate the backlash between the idler gear and the crank gear. I test it in several places but it usually runs pretty consistent. Next I  install the camshaft and cover. The  indicator then goes inside the crankcase where I can indicate the total movement of the cam gear.
So I end up with two measurements, as an example
Idler to crankshaft lash, .016
Total lash at the cam gear .024
The lash between the idler and cam gear is the difference between them or .008

I like to get it down as close as possible without bind which is an absolute no-no. .004 is about as much as I will personalty settle for at each mesh or .008 total.
I can only wish that I had paid enough attention in some geometry and math classes to calculate the movement needed. Since I did not I must rely on seat of the pants, aka guessing and making the bolt. I have a jig in mind for this but in all likely hood it will never come to pass.


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Quinnf

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Re: Jkson 6/1 rebuild
« Reply #115 on: February 26, 2015, 08:34:03 AM »
No worries.  We're all learning.  I spent my working life wearing a lab coat and support stockings in pharmaceutical research, so I'm no professional wrench-turner.  I'm glad to learn something new. 

Gary, I made my offset bushing just like you did. 




I turned down the idler gear shaft and installed the offset bushing (bronze, in my case) until the noise went away, and called it good.   


The thing that I don't get about measuring gear backlash in common involute spur gears is that the point of contact between adjacent gear teeth moves along the length of the tooth, and without a meshed pair of gears right in front of me, I'm at a loss to figure out how to measure the backlash.  So like Gary, I used my ears and hoped for the best.  Gears are deceptively sophisticated machines.  Just getting the nomenclature right is a challenge.  So I'm all ears. 




Quinn
Ashwamegh 6/1, PowerSolutions 6/1 "Kit" engine, and a Changfa R175a that looks like a Yanmar I once knew

Gippslander

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Re: Jkson 6/1 rebuild
« Reply #116 on: February 26, 2015, 11:12:22 AM »
How do you stop the off -centre  bush from rotating around the turned down shaft ? Did you use loctite on it ?  Mike
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32 coupe

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Re: Jkson 6/1 rebuild
« Reply #117 on: February 26, 2015, 12:56:11 PM »
Quinn,
No, I made mine just like YOU did !!

I saw you pics and like the idea and thought I could handle that with my limited machining skills.

Mike,
I used a drop of locktite when I got it where I wanted it.

Gary
Metro 6/1 turning a ST 7.5 KW gen head
Changfa 1115 turning a ST 15 KW gen head
Ashwamegh 2/25
John Deere 110 TBL
New Holland TC 30

"I was sitting here reading this thinking what an idiot you are until I realized it was one of my earlier posts !"

38ac

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Re: Jkson 6/1 rebuild
« Reply #118 on: February 26, 2015, 01:40:49 PM »
Quinn,
OK I get your question now. As the contact area moves down the tooth the lash remains the same, when it does not, such as in worn or improperly made gears the gear set is noisy in operation. Not noisy as in the click clack of excess lash but  a constant whirring noise.

Maybe this link will help, also has suggested lash for various pitches. Note that it says that reversing loads require tighter lash, that is what we are  dealing with in the cam drives. In my writings, the lash is measured at a 90 angle to tooth travel. I am not a gear expert so I wasnt trying to hit a number that was calculated from a table, as somebody said, get rid of the clackity clack and you have done right  ;D
www.engineersedge.com/gears/gear_backlash.htm

For those curious this picture explains the various planes used in the prior link.
upload.wikimedia.org/wikipedia/commons/f/fb/Normal_plane.JPG
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BruceM

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Re: Jkson 6/1 rebuild
« Reply #119 on: February 26, 2015, 02:55:33 PM »
For measuring the gear lash prior to ordering one of Dave's offset idler bolts, I used a method that I think Ronmar suggested- a 3/32" music wire extension against a tooth, leading out of the case and to a dial gauge.   It was fussy to set up but worked great. After learning what .004" feels like, I wouldn't use that again.

My Metro needed a .055 offset bolt, so you can imagine how sloppy it was.  It did not totally eliminate the clack- clack, though.  That seems to be caused by the tappets slapping down on the cam.  Hotater found it could be eliminated temporarily by adding fine lead shot to the pushrod cups, and Ronmar reported it could be eliminated by adding a light spring to push the tappet downward while there is lash.  You can confirm that by pushing lightly downward on the rocker arm opposite the valve.  I foolishly thought the clack could be remedied by having less mass in the pushrods so the tappet would follow the cam better and made a pair of carbon fiber tube pushrods.  That did nothing, of course.

Alas, I have neither the equipment nor skill to make an offset idler bolt, or to turn down the stock bolt for a bushing. 

I have a lovely XYZer 0.040" offset idler I'd like to trade for an 0.015 to 0.020.