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Building a 16H big end bearing

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I've bought NOS (16h WD) big end crank pin and outer bearing race, and after a bit of a struggle, managed to get the race into the con rod.  I then bought new 1/4" x 1/4" rollers, and found that two rows of 16 rollers fit the crank pin, but the assembly doesn't fit the outer race/conrod.  It's not that it's tight, it simply doesn't fit.

I haven't measured the rollers yet, so maybe they are not what they seem.  Anyone got any advice? The original 1940 rollers from this crank assembly are beyond salvage.

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The interference fit in the rod eye will usually mean that it needs honing to restore clearance.  Most Norton (or other single cylinder) specialists will be able to do it.

 

 

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Hi Russ,

   There were at least 2 companies making these bearing assemblies, especially during WW2, and there are slight variations in diameter of the pin and consequently the inner size of the outer ring. This allows a bigger radial gap between the rollers but of course each set must match and it sounds like you might have a mismatched set. Rollers for a new bearing should measure 0.25" but oversize rollers are/should be available for reconditioning part worn bearings. If you do have a mismatched set you will most likely have to start again as I think it will be too much to hone.

Thanks for the comments - I'll measure it all up, but does anyone know if under-sized rollers are available  - that might be my solution? 

Another question - I've seen Big End assemblies advertised as 'crowded'......I can fit 16 rollers per row (with a decent circumferential clearance) - am I 'crowding' the bearing? 

 

thanks all, 

 

Russ 

 

In reply to by richard_payne

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Richard - interesting option. A shallow re-grind (or as you say 'hone') might do it.  What do you reckon the case-hardening depth of the WD bearing outer race is? 

 

Russ 

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Hi again Russ,

   I have 2 big ends with different dimensions so if I get time tomorrow I will measure them up. All the post 1931 to '47 SV and OHV big-ends use 32  1/4" rollers, so the easiest option would be to grind the crank-pin but at a guess I would think the case hardening will only be about 20 thou deep. The next smallest easily available rollers will be 6mm which are approximately 11 thou smaller. The term "crowded" refers to the rollers packed in together as opposed to running in a cage. The crowded roller type is the cheapest and poorest design.

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Hi again Russ,

   I found out the 2 big-end bearings, both R&M, today and I think I have found the differences. There are 2 distinct bearings although they are interchangeable as sets from 1933 to 1963. The early bearing uses 2 rows of 16 1/4" x1/4" rollers and the crankpin journal measures 1.048" and the thickness of the outer ring is .225". These bearings had been known to fail with the crankpin shearing due to torque strain. Later bearings, probably from 1948 onwards, have a bigger crankpin diameter of 1.133" and an outer ring thickness of .18" which allows 2 rows of 17 1/4" x 1/4" rollers to be fitted. These measurements were taken with a digital caliper gauge, so should be fairly accurate. Check your parts and see if any of your parts are the same as above, but as I posted earlier these should be matched parts as manufactured, and as you can see by the measurements with-out re-machining and re-hardening it's not do-able.

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Bottom line - never believe that parts bought around the world are to spec - measure everything before building. 

I bought two NOS 'genuine WW2' crankpins and outer races from a dealer in ex-WD parts in France (nice guy). I built the troublesome big-end bearing with one set of these parts using 1/4" x 1/4" rollers I sourced in the UK. Didn't work.  

I measured the other unused crankpin, and an original 1940 one, and the bearing dia was 26.65 mm on both of them......when I measured the same dia on the crankpin I was building, I found it was 27.2mm......that completely explains the issue.  All other dimensions on this crankpin are ok.

Result - rebuilt the bearing tonight using the other NOS crankpin and it's perfect. Happy days.  

 

In case anyone wants the dimensions, here are mine: 

  • Standard outer race fitted in 8" conrod, bearing ID =39,50 mm average
  • Rollers are a fraction under size at 6,32mm average (0.248") average 
  • Crankpin OD = 26.65 mm average 

If you do the simple clearance calc, you'll get the wrong answer as nothing is perfectly round, so the actual clearance will not be the simple subtraction of the above. But I reckon this is all OK.....after all, these things were rebuild out in the desert in Africa in 1942, and they didn't have digital verniers!

Anyway, I'm learning.......

 

That's very interesting Richard - lots of traps to watch out for when buying parts from all over the place.  Your suggestion of the later crankpin doesn't fit my measurements (see my latest post on problem resolution), so I think I have managed to buy two ex-WD crankpins, one nominal and one over-sized.  The seller didn't know what he was selling, or it's manufacturing error. Caveat emptor.

I also just sold an alleged WD 16H con-rod on Ebay that turned out to have the bearing OD a good 1/8" over standard  - so that might have been the later improved standard you suggest.

Anyway, thanks for all the info. An education for the next one....

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Hey, guys.

I'm sorry to resurrect a thread, but my question is right along the lines of what's been discussed here, so I thought it would be best to assemble the accumulated language in one tidy location.

As part of the engine refresh of my 1948 Model 16H, I am rebuilding the crank pin and need some guidance on the loose roller needles.

After splitting the cases and examining the crankpin and bearing, I found the pin OD and outer race ID measured 1.029” and 1.529” respectively, which yields a difference of 0.500” precisely.  A few of the rollers measured spot-on at 0.025” but several were smaller.  

  1. Is the intention here to run 0.025" diameter needles at zero clearance?  I can fit two rows of 16 needles each, and there's still a little bit of slop due to the wear on several of the needles.  
  2. One of the needles measured 0.025" x 0.510" whereas all the others measured 0.025" long.  Is it ok to run 16 "long" needles instead of 32 "short" ones?  
  3. I understand that when running two rows, it's desirable to have a ring shim between the two rows.  Is that the case?  When I took down this engine, there was no such shim.  Perhaps a shim of 0.010" would yield the 0.0510" dimension, the exact shoulder-to-shoulder dimension on the crankpin.  
  4. Where can the loose roller needles be sourced?  
  5. If this shim is required, do you guys know where one might source such a shim?  
  6. Is there anything else I need to know? ​​​​​​​

Thanks!

-Robert

 

 


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