Author Topic: Motor strip  (Read 5483 times)

Offline tlmark

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Re: Motor strip
« Reply #105 on: 30.04. 2018 14:30 »
 *eek*  Oh Yes these will do  *smile* these will do very nicely  *woo*

Online muskrat

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Re: Motor strip
« Reply #106 on: 30.04. 2018 14:39 »
Look too good to be hidden inside a motor.
Cheers
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Offline tlmark

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Re: Motor strip
« Reply #107 on: 30.04. 2018 14:51 »
Look too good to be hidden inside a motor.
Cheers

Yeah I was thinking exactly the same thing  *smile*

Online Greybeard

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Re: Motor strip
« Reply #108 on: 30.04. 2018 15:17 »
*eek*  Oh Yes these will do  *smile* these will do very nicely  *woo*

Woot!  *yeah*

Offline tlmark

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Re: Motor strip
« Reply #109 on: 03.05. 2018 15:23 »
Hmm so with a nice long weekend approaching and good weather predicted
I took the day off to start putting the motor back together.

Sadly that’s not gonna happen. I don’t know why but when I stripped it it had -.20 undersized big end shells. But now when I Reassemble it with new -.20 shells the conrods wont move even before I’ve torqued it up  *problem* 

Online Greybeard

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Re: Motor strip
« Reply #110 on: 03.05. 2018 15:27 »
...when I stripped it it had -.20 undersized big end shells. But now when I Reassemble it with new -.20 shells the conrods wont move even before I’ve torqued it up  *problem*
If you have the old rods compare against these ones to check if someone has removed metal on the cap faces.

Offline tlmark

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Re: Motor strip
« Reply #111 on: 03.05. 2018 17:10 »
GB thanks I’ll have a look, had to walk away for a bit and have cuppa ;)

Online berger

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Re: Motor strip
« Reply #112 on: 03.05. 2018 19:54 »
i have not been to the pub, that's tmow *smile* as greybeard says do a check . I will bore you with my experience many moons ago with rods ,firstly the rods I was re fitting on a crank did exactly what you say yours are doing and locked up way before full torque. do not worry my friend because once you have put full tightness on you may well find they purr round the big ends  as mine did*good3*. BUT!!!!!! I also fitted some minus 10 shells on a crank with some rods that came out of an engine a long time ago and they stayed locked solid  *pull hair out* *bash* I took everything to a very good engineer and he told me exactly what had been done to the rods. in the old days a knocking big end would be cured by shaving a few thou off the cap or rod and charging customer full price for repair[ the lousy@@@@@@@@@] very bad thing to do but it stopped the knock and they were only work and back transport so they got away with doing it for years. the engineer who made these rods round again did a very good job, but then one piston was about 8 thou higher than the other a TDC but that engine got thrashed and told me it was very happy with its differences. if it wasn't it wouldn't be running present day. so don't panic and I hope all comes out in the wash as they say *grins*

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Re: Motor strip
« Reply #113 on: 03.05. 2018 20:47 »
Yes berger is right. They tighten up at first then when correct torque is reached it's all free again.
They are built to have crush on the bearing. If you put the shells in the rod and push the cap on you should notice a gap (a few thou")between rod and cap.
Cheers
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Offline Sluggo

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Re: Motor strip
« Reply #114 on: 03.05. 2018 21:31 »
Hate to be pedantic here......... *eek*  But please tell us what Mr Micrometer has to say. Even some Harbor freight digital calipers if you take your time and finesse it will tell you the tale.   *work*

Math is brutal.   It pains me to think of someone cranking down on a connecting rod in the vain hopes a tight fit will loosen up.  (perhaps it will  but it would be prudent to measure first)

I cant speak for all BSA rods, but my experience on other British bike connecting rods is with only a few exceptions there is no such thing as a concentric rod after its been in service and then removed.

 (measuring tools never ever lie about this, If you think they do then R2 Operator, IE: Remove & replace the person using them)

The proper way to resize a rod and ensure a perfect bearing crush and contact all the way around is of course measure the rods first. (Check for straightness of course too) with the cap torqued on.  If the hole is out of round at all, then qualified machine shop carefully removed a small amount of material from rod and cap and then retorques back together and HONES the hole to true.

These guys explain it better than me.........

See: http://www.enginebuildermag.com/2005/05/connecting-rod-reconditioning-more-to-it-than-you-might-think/

(its for auto apps, but the methods are the same, and the article raises a excellent point. Have you checked the rods for rockwell? IE: Hardness?)

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Online duTch

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Re: Motor strip
« Reply #115 on: 03.05. 2018 22:14 »

 When I first rebuilt my engine late '70's, the big-end was re-sized but when I re-nuilt it last time 2010-2012, I realised the caps were machined out-of-whack so wee never going to be right without serious machining- that's when I lashed out on Thunder Rods....

 Sluggo- a slightly off-topic but related question-I posted about this some time ago-I'll try and find it, but in the meantime; Same time as above^circa2011^ the machine-shop guy told me my crank was 'oval' but not in the usual way...even though it measured within specs and appeared round, he explained that there's a condition that is 'unique to Airplane engines' (not sure if he's fulla or not, but did find reference to it on the net at the time, but not now), where the crank pin becomes kinda shaped like a rotor from a Wankel type rotary(greatly exaggerated), where no matter wherever is measured diametrically, all measurements are equal....does that make sense and do you know of or about it ?

   ** Just yes or no will suffice until I find the thread/post   *whistle* *smile*

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Offline Sluggo

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Re: Motor strip
« Reply #116 on: 03.05. 2018 22:50 »
" Sluggo- a slightly off-topic but related question"........ errr No.  Would love to know what thats about, sounds improbable so would like to see source material.

There is many apps in modern engines with "Stretchy" bolts and hardware, One time & throw away, There IS such a thing as cam ground pistons and bores that under torque, heated operating temps and loads the parts revert from egg shaped to round (Neat trick that!) And the HD Evolution Sportster engine is a marvel of engineering worthy of study how they pulled off that trick.

(Slightly more than just no eh?)  But most recip piston type aircraft today and in the past are either Lycoming or Continentals of varying sizes.  Flat 4s and 6s and are basically glorified VW engines.
They also run very low RPMS (1500-2800rpm) but engine loads are high based on algorithms of propellor length and pitch.

See: https://www.lycoming.com/engines

But, you made me look and cannot find any material related to such things. (A&P license holders have to access resource materials before initiating work)  But there is such things as AC and ADs, A Advisory circular is FYI in nature and correct if needed, But a AD is directory, I dont understand why this is an AD, but fun reading all the same.
See: http://www.dtic.mil/dtic/tr/fulltext/u2/a257220.pdf

" SYNOPSIS
In this paper, the dynamic performance of the Ruston and Hornsby VEB diesel engine
connecting-rod bearing with circular and out-of-round profiles is analyzed. The effect of cavitation
M,., is considered by using a cavitation algorithm, which mimics JFO boundary conditions. The effect
,o of mass inertia is accounted for by solving coupled nonlinear equations of motion. The journal
profiles considered are circular, elliptical, semi elliptical and three lobe epicycloid. The predicted
journal trajectory and other performance parameters for one complete load cycle are presented for
all of the out-of-round profiles and are also compared with the predictions for the circular bearing"
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Offline tlmark

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Re: Motor strip
« Reply #117 on: 07.05. 2018 13:47 »
After much "Effin and Jeffin" I have my rods bolted on!

I must have put them on and taken them off 20 times. And the same result only when I had tired of struggling to get the end caps over the bolts with a rubber mallet which then caused the big end shells to move or fall out. again! I took an 8mm reamer to the 5/16" hole.
And thus be able to push the end caps on by hand and low and behold everything went together perfectly  *woo*  it might not have been the right thing to do but my patience was too thin to care.

And as it has been a nice long bank holiday I have the bottom end built and ready to drop back in the frame.  *smile*

Offline tlmark

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Re: Motor strip
« Reply #118 on: 07.05. 2018 19:08 »
Pix of the progress so far and a vid of the rods

https://www.youtube.com/watch?v=J15Na7sLm8g 

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Re: Motor strip
« Reply #119 on: 07.05. 2018 20:27 »
Oh bother! The reason their tight on the bolts is for alignment, a little machine oil and pushing them on squarely should only need a light tap. The shells should be a snap fit into the rod and cap so should not fall out with the gentle persuasion on the caps. In the video is that dry or with oil? Seem a little loose for my liking.
Cheers 
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
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