Author Topic: is an offset idler shaft available to buy or have one made?  (Read 2400 times)

davesiegler

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is an offset idler shaft available to buy or have one made?
« on: November 26, 2017, 10:55:14 PM »
I think its the cam gears  that sound so terrible. very "clattery" a random sort of clatter that doesnt go away when valve lash is dampened by fingers.
tommorow morning i will take the door of and check the backlash and any wear pattern, but it didnt make me feel warm and fuzzy when i assembled it so i bet ill need an offset pin.
This is a new engine, 10/1, only has about 5 hours of runtime with only three or so hours pushing a 3800 watt load.
thanks to everyone involved in posting all this valuable information. its nice not to be running totally seat of the pans with my new powerplant.

32 coupe

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Re: is an offset idler shaft available to buy or have one made?
« Reply #1 on: November 27, 2017, 01:13:46 AM »

I made a few offset bushings in the past that have worked well. PM if interested.

A bronze gear is also available.

Gary




Metro 6/1 turning a ST 7.5 KW gen head
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38ac

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Re: is an offset idler shaft available to buy or have one made?
« Reply #2 on: November 27, 2017, 01:23:58 PM »
Nobody is building them in mass for sale that I am aware of.  I build them on a case by case basis for engines built in the shop.  It's one of those deals where the demand isnt there to make a bunch of them and to make one puts the cost where few would be interested. The other issue is the they need to be made for the individual engine to be truly right.
 Takes me about 3-4 hours to knock one out on my manual engine lathe and I have never sold one to anyone who asked because I wont run the lathe for nothing. I am not a snob nor am I about money, I am just too damn busy and dont like running the lathe well enough to run it for giggles. 
You would get the best fit if one was made to fit your engine and clearances. Around here there are lots of hobby lathe owners,  put an ad on your local Craigs List. "wanted, somebody to make a simple part on a metal lathe" or similar. Ill bet you get a response.
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dieselspanner

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Re: is an offset idler shaft available to buy or have one made?
« Reply #3 on: November 27, 2017, 04:54:02 PM »
Somewhere on here is a post from Ed Dee, probably part of 'The Lister Chronicles' marathon, where he describes making an offset bush up.

It means drilling and maybe reaming the bolt hole in the crankcase over size but is much less work than knocking out a whole bolt.

I had one made whilst working out of a shipyard down in Spain last year, haven't got around to fitting it yet.........

Cheers
Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

BruceM

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Re: is an offset idler shaft available to buy or have one made?
« Reply #4 on: November 27, 2017, 05:56:09 PM »
 Xyzer (Dave) was the one who sorted out the whole issue of failing idlers and the error in Rajkot idler bolt hole placement compared to Lister CS many years ago.  Xyzer made a few batches of large offset bolts - my 6/1 needed something like 0.055 inch offset. They were very high quality work, as were the hollow dippers he made, which I also use.  It was a hugely generous contribution he made to CS clone/ Listeroid users; something like 14 years ago.  His contribution solved the problem and failed idler gears were no more.

The offset bushing seems a good approach for the diy solution, as it lets you test fit different offsets.  Boring out the case hole is the only way to do it for larger offsets. I'd bore it to a standard size then very carefully drill offset holes in stock round pieces via carefully setup drill press, or use my wood lathe and 4 jawed chuck for the offset drilling. Less than ideal but allowing for a lot of duds (benefit of bushing approach) it should work.

For smaller offsets you can turn down the stock bolt and add an offset sleeve.  32coupe made some very nice sleeves with turned down bolts that use the stock crankcase hole.  They are a good solution for smaller offsets if he has some left.  I used on for my neighbor's DES 8/1 propane conversion project and it saved the day.  Much appreciated, 32coupe! 

Very impressed that you did your homework, DaveS.  If you have a large amount of clatter that isn't from the tappets and valve lash (finger test) then you likely have the need for a large offset like 0.040 or more.  You should be able to find old posts on doing lash measurement.  After doing it once, you can do it just by feel. 6 mils (typing paper) is a nice fit. 



« Last Edit: November 27, 2017, 06:15:22 PM by BruceM »

davesiegler

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Re: is an offset idler shaft available to buy or have one made?
« Reply #5 on: November 27, 2017, 11:51:21 PM »
BruceM you mean .006 " of backlash or gear  tooth to gear tooth clearance? eigther way it was significantly more then that. Ha Ha !!
Im going to have to do something about it soon. Its charging the batteries 'm using to make this post. no powerlines here.

32 coupe

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Re: is an offset idler shaft available to buy or have one made?
« Reply #6 on: November 28, 2017, 12:47:04 AM »

Bruce, thanks for the kind words.

My work is not on par with xyzer or 38ac but they do the job.

I have made 5 for people and everyone has had good results with no problems.

I have never charged anyone, and have even shipped them at no cost. I only ask for feedback
and a post here with the results.

Dave, where are you located and how much offset do you think you need ? I have sent 2 bushings with
different offsets for those without an idea of what they need and it has always worked out.

If you need help PM me and perhaps I can help.

Gary
Metro 6/1 turning a ST 7.5 KW gen head
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BruceM

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Re: is an offset idler shaft available to buy or have one made?
« Reply #7 on: November 28, 2017, 01:59:19 AM »
Yes, 0.006 inch lash is a reasonable figure.  Close counts.  I think Gary's offset bushing/bolt is about 0.024 max which won't be anywhere near enough if you are measuring say 0.032+ to the crank gear and 0.020+ on the cam gear with the crank/idler locked up on a rag. The offset needed is a bit more than the sum of the two (at least 0.055) since it has got to move not just towards one but in the middle of the two.

Just trying to help save you some time.  Measure your lash to figure out the real situation.  It's tricky but can be done with music wire extensions to a dial gauge...or you can just do it by braille with a feeler gauge at the crank and learn how various amounts of lash feel as you move it by hand.

davesiegler

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Re: is an offset idler shaft available to buy or have one made?
« Reply #8 on: November 28, 2017, 07:40:23 PM »
i know braille...

32 coupe

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Re: is an offset idler shaft available to buy or have one made?
« Reply #9 on: November 28, 2017, 09:00:22 PM »

"close counts"
That pretty much covers it.

On my twin I found the idler gear was not round. The bronze gear took care of
that part of the problem.

The way I make the bushing I can't get more than about .040
I think I ended up with about .030 on the twin before I was happy.

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 !"

EdDee

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Re: is an offset idler shaft available to buy or have one made?
« Reply #10 on: November 29, 2017, 11:11:19 AM »
As an experiment, I took another way at it... Bored the Idler gear mounting hole in the crankcase and bearing housing out as much as I could, then used an offset bushing made out of MS to throw the existing idler shaft in the direction I needed...Got about 2mm of offset at max, ended up with about 1mm offset on the bushing if I remember correctly.... Once the hole is bored open, put the gear and shaft into place, bottoming out on the crank and cam gear... Measure how far out of center it is with a vernier and back off the measurement slightly so things dont bottom out when installed... I am lazy, and this was the easiest way I could do it... Seems to work quite well too....

Cheers
Ed
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