Author Topic: skf NJ206 ECP bearing  (Read 510 times)

Online edboy

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skf NJ206 ECP bearing
« on: 23.07. 2020 21:37 »
this  polymide cage bearing looks superior to the more common nsk 306 but at a better price. so has anyone fitted this skf bearing to their a10?
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Offline muskrat

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Re: skf NJ206 ECP bearing
« Reply #1 on: 23.07. 2020 21:47 »
G'day Ed.
Looking at their drawing it has no lip on the outer so doing the end float of the crank would be impossible.
Cheers
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Online edboy

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Re: skf NJ206 ECP bearing
« Reply #2 on: 23.07. 2020 22:06 »
hi muskrat. i looked at the catalogue again and prefix nj is for the single sided outer lip we use in our bikes. it also has the single sided inner so fitment looks ok. you must admit its a nicer looking bearing than the nsk.
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Offline Swarfcut

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Re: skf NJ206 ECP bearing
« Reply #3 on: 24.07. 2020 09:18 »
 edboy.   Something not quite right here with the bearing description or design interpretation.

 Here are three that do the job.

 NF    type is standard fitting. Rollers stay on crank. Single lip on outer race, two lips on inner.

 NJ    type has two lips on outer race, single lip on inner race adjacent to crank cheek. Rollers stay in crankcase.

 NUP type. As NJ type but with an extra demountable outer inner race lip. When the cush drive is tightened down this eliminates crank float to that  within the bearing. Very clever design slightly more expensive, but retains the ease of setting the initial crank float as the rollers stay in the case, allowing a less obstructed application of your bearing puller to the inner race on the crank. Plus no end float, positive fixed crank location but an initial running clearance at the timing side set up as usual with the shims.

 More information here
https://www.bearingboys.co.uk/N-Type-Cylindrical-Roller/NUP206-ECPC3-SKF-Cylindrical-Roller-Bearing-30mm-x-62mm-x-16mm-2834-p

 Note..Schematic diagram is generic, and does not show the true layout or profile of the various elements of construction


  Swarfy.
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Offline muskrat

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Re: skf NJ206 ECP bearing
« Reply #4 on: 24.07. 2020 10:58 »
G'day Swarfy
The only problem that may occur with that bearing is the gap between the crank and thrust face of the bush. With the standard 1,1/2 thou end float the gap is close and restricts oil from coming out there and go where it's supposed to. If a crank with the original set up needs a 10/15/20 thou shim and that bearing is used the gap is larger and oil will escape.
I may be wrong but that's my spin on it.
Cheers
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Offline Swarfcut

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Re: skf NJ206 ECP bearing
« Reply #5 on: 24.07. 2020 11:21 »
    G'day Musky.
     Yes you're right. There needs to be a gap between the crank and bush for expansion and also to allow an oil film to be maintained between the bush face and the crank cheek.  As you say too wide a gap offers the chance for oil to escape.

    Depending on source, anything from zilch to 3 thou on a cold motor is what folks try for.  The beauty of the NUP design is that you set this gap as specified in the usual way with the usual shims. The bearing restricts axial movement to that within its manufacture, once the cush nut is tightened,  there is little float but a running clearance remains between crank and bush face because that has been set as per normal practice with the shims between inner race and crank. On and off of the inner race for shim selection is far easier, no rollers in the way.

 The only downside is the cost, and the need to ensure the cush nut remains tightened to the high torque figure.

 Cheers.

 Swarfy.
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Offline muskrat

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Re: skf NJ206 ECP bearing
« Reply #6 on: 24.07. 2020 21:13 »
G'day Swarfy.
Yes I see your point. Still setting the end float would certainly be required before locking it all up.
My take on the endfloat isn't really for expansion but contraction. At rest when the motor is cold the endfloat is there so the crank won't lock up. When hot the cases being alloy will expand more than the crank giving more end float. That bearing would be beneficial in stopping the crank "floating".
I'll give one a go in the next refurb of the A7 and fit an oil pressure gauge while I'm there to check its performance.
Cheers
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Online edboy

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Re: skf NJ206 ECP bearing
« Reply #7 on: 24.07. 2020 21:38 »
thats the spirit muskrat.
my interest is that its c3 tolerence and £30 which is good value. i have a few engines and would be happy to slog one up and down the motorways at a constant 70mph.
i also use a flat needle race and thrust washer between the engine sprocket and outer crankcase to oppose the push and pull of the oil pump drive.
8,000 miles without problems so far but i m not going to push that idea on anyone here.
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Offline Swarfcut

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Re: skf NJ206 ECP bearing
« Reply #8 on: 25.07. 2020 07:56 »
     G'day Musky.   Whoops. Yes it's not for expansion, its a cold running clearance, which will increase as the cases warm up. Forgot about the cases and their different expansion rate. Anyone ever compared the end float hot and cold on a standard set up? After all that careful shim selection the hot running endfloat could be a bit of a shock.

   edboy's thrust washer sounds interesting. Just trying to figure out how its done.

 Cheers

 Swarfy.
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Offline RDfella

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Re: skf NJ206 ECP bearing
« Reply #9 on: 25.07. 2020 10:04 »
If I recall correctly, Velocettes used taper rollers and were set up with preload to allow for case expansion.
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Offline sean

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Re: skf NJ206 ECP bearing
« Reply #10 on: 04.08. 2020 02:31 »
same with pre 99 harleys used tapered crank brgs.....I think the only reason they changed on the twin cam engine was to save money on set up

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Online BSA_Owen

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Re: skf NJ206 ECP bearing
« Reply #11 on: 04.08. 2020 06:58 »
would there be a preference for a fiber cage over brass?
I can get the NUP 206 EMC3 pretty cheap ($58 + GST) through a local supplier which might be worth a shot in my A10 build.
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Offline sean

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Re: skf NJ206 ECP bearing
« Reply #12 on: 04.08. 2020 13:46 »
would there be a preference for a fiber cage over brass?
I can get the NUP 206 EMC3 pretty cheap ($58 + GST) through a local supplier which might be worth a shot in my A10 build.

if you mean the nylon cage over steel ...the advantage is the nylon one can be taken apart and the inner race removed with a puller the steel cage fits so tight to the crank face almost impossible to remove without damage to the cage  ....depending on interference fit  .......fitting and removal will likely have to be done several times to get the correct end play adding or removing shims .
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Offline chaterlea25

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Re: skf NJ206 ECP bearing
« Reply #13 on: 04.08. 2020 20:49 »
Hi All
A premium branded bearing is always my choice,
The main bearing in my SR has a polyamide cage and no complaints after all these years and miles
Currently rebuilding the Ariel Huntmaster bottom end and it has a bronze cage bearing, nice and tight on the crank
I ground a bolster type chisel to a fine  edge and thin enough to fit in behind the bearing cage without touching it
It worked a treat getting the bearing to start moving then a slightly thicker wedge got it out far enough to hook some puller legs in behind the bearing inner
There were no shims behind the bearing but I would think any would be damaged with my method ???

John
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Online BSA_Owen

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Re: skf NJ206 ECP bearing
« Reply #14 on: 05.08. 2020 04:28 »
would there be a preference for a fiber cage over brass?
I can get the NUP 206 EMC3 pretty cheap ($58 + GST) through a local supplier which might be worth a shot in my A10 build.

if you mean the nylon cage over steel ...the advantage is the nylon one can be taken apart and the inner race removed with a puller the steel cage fits so tight to the crank face almost impossible to remove without damage to the cage  ....depending on interference fit  .......fitting and removal will likely have to be done several times to get the correct end play adding or removing shims .

Hi Sean no brass not steel. It is NUP prefix still so has the removable loose flange ring.
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