Author Topic: 26 ew rods  (Read 2833 times)

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Offline shuswapkev

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26 ew rods
« on: 22 Dec 2014 at 09:55 »
next step on my new douglas...

the conrods...my rods have the races a bit loose in them...what is the best way to sort this out
I was either going to purchase a 1/4 wide ballrace ..and just use that... or turn some new races out of steel and harden them...but make ,m a bit oversize... and just press into the oval hole... and hone the centre out... ??
with a lap??
or should I use a lap and make the hole round again before fitting an oversize race??

  this douglee is needed to oil the roads of queensland again

Offline Doug

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Re: 26 ew rods
« Reply #1 on: 22 Dec 2014 at 14:29 »
Shuswapkev,

Loose bearing races in the 350EW connecting rods are quite common. All sorts of horrible repairs are seen such as center punching and tack welds to try and retain the race. You can bore the connecting rod out slightly and make an oversize race, but the reason the connecting rod stretched in the first place is that the cross sectional area is insufficient. It will eventually stretch again. Douglas recognized this problem and the later connecting rods eliminated the bearing race insert and used a direct carburized race. They also went to 1/4 inch rollers. You can use the 1/4 inch rollers and a special (thick wall) rod race to reclaim the EW style connecting rods. The heavier race will be more resistant to distortion and working loose.

You may want to review this post here:
https://www.douglasmotorcycles.net/index.php?topic=109.msg259#msg259

About 2/3rds of the way down it talks about recovering EW connecting rod bearings.

-Doug

Offline oily bloke

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Re: 26 ew rods
« Reply #2 on: 22 Dec 2014 at 16:49 »
Hi,
Doug's suggestion is perfectly valid, however, I went my own way. The big end bearing on the crank itself is a hardened bush pressed over the big end pin and the outer race is how Doug describes. I replaced both with through hardened sleeves and once pressed in place were ground to suit metric rollers. I had to cut the available rollers and gently ground then lapped to length. Took ages but I now have a free running, noiseless crank.
Cheers
Andy

Offline shuswapkev

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Re: 26 ew rods
« Reply #3 on: 22 Dec 2014 at 20:08 »
thanks heaps for that..
   sounds like I need to make some new races..and lap to size..our local bearing supplier has a bunch of 1/4 inch rollers...
I have made up laps to do matchless and bsa cranks and worked surprisingly well...

  the only thing I,m unsure about is whether to resize the rod..the hole is obviously oval...so...make a lap and get that as round as I can...or press in a race and lap that round...   I "think" I would be better off resizing the hole first...


that is one skinny little rod...

Offline oily bloke

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Re: 26 ew rods
« Reply #4 on: 23 Dec 2014 at 08:01 »
I was lucky in that my rods were only slightly oval and easily lapped to round.
be careful not to overdo the interference fit in the outer race in the rod as the lack of 'meat' on the rod can cause it to crack.
Hand lapping is not advisable as the rod is so narrow it is easy to end up with a barrel shape inside the rod eye.
Cheers
Andy