A10 main bearing quality

[A10Boy]

 Modesty forbids...  

Ohh and there was a nice camshaft that went to a gent in scotland recently........

[MG]

I received my parts from SRM today (well, everything except the con-rods, but at least I can start work on the bottom end now).

The roller bearing they sent me is a Japanese NTN NF206E. The suffix E makes it a high load capacity version with increased roller diameter.
So far so good, but what I'm not completely happy with is the resin roller cage. The picture on the SRM website to me clearly looks like a brass cage, but judge for yourself:
http://www.srmclassicbikes.com/catalogue/index.php?target=products&product_id=138

I am not saying that a plastic cage is not going to work, assuming it is temperature-stable and oil-resistant, but just thought I'd mention it, as I think a picture is part of an item's description and you should get what you see in the end.

[bsa- bill]

Also says USA if I'm not mistaken MG, but most are plastic these days and they seem ok, they would probably take it back but then you would just be adding return postage to the cost of the item.

Andy - sorry I meant to reply, item as described, positive feedback left and now residing in it's new home

[orabanda]

A very nice feature of the resin (plastic?) roller retainer cage, is that it makes the task of setting the crankshaft end float very easy.

This is because the rollers can be popped out from the retaining cage one by one, leaving the inner bearing race on the crankshaft. In the next step, a standard split bearing puller can be placed around the inner race, and it can be pulled off easily, without any damage.

Finally, the bearing can be re-assembled by putting the cage back in position, and popping the rollers back in place.

I have just set up an A10 bottom end this week, using the SRM bearing;a sometimes difficult task has never been easier!

I also had the crankcase halves set up in a lathe  for the line boring of the bronze outer / white metal inner timing bush, (after making a supporting fixture from an aluminium bellhousing) and am rapt in the final result; bottom end is perfectly aligned and spins like a top, with 0.0015 " clearance between journal and bush.

Other point of note is that I could measure a bit of ovality in the bore for the bushing, in RH crankcase half. I checked the bore because the old bush would slide in from one side, but had an interference fit on the other.

I asked the machinist to bore out the crankcase half, until it cleaned up; it took 0.012" to clean up (concentricity!).
In the future I will adopt this practice always, as clearly ovality is likely to be an issue in old crank case halves.

I then machined up a timing bush from phosphor bronze (had a billet lying around) and sized it to give 0.002" interference on the crankcase. Then I poured babbit (white)  metal on the inside, left a couple of mm undersize on the bore, and shrunk into the crankcase.

The bronze is a better choice than steel, because the co-efficents of expansion are much closer between aluminium and bronze, than for Al and mild steel.
Therefore, it is more likely to maintain an intereference fit (and consequently maximum oil pressure!) when the engine is hot.

By machining in the lathe, we were able to clock perfectly on the primary drive bearing recess, then bolt up the RH half, and machine the timing bush in line.

Richard

[muskrat]

G'day Richard,
                        I'll give you your 1st karma for that.
I remember using a bearing like that years ago and did the same.
But I've never checked for ovality in the case/bush bore. I will in future.
Cheers

[orabanda]

Muskrat,
Your'e sweet!
A few pics to complement explanation above:



LH crankcase bolted to bellhousing. This was then clocked in lathe, to priary drive bearing



Once aligned, RH half bolted on and then line bored

Prior to this, original bore machined until it was round again. Here it is with the new bush installed.



Here is new bush (pb outside, white metal inside), machined to be oversize on re-bored crancase



Another pic of installed bush



Richard

[MG]

Richard, great idea to remove the rollers for pulling the race off, and nice work with your crankcases! 

[iansoady]

Nice job.

I might struggle to do that on my 3.5" Granville.......

[manosound]

Richard,

A quick question: What assures the poured-in babbit adheres to the phosphor bronze?

[MG]

Usually you would tin the inside of the bush prior to casting the babbit into the pre-heated bush. This makes sure it will adhere properly.
Of course I don't know how Richard (orabanda) did it, but from what I've seen of his work so far, I'm sure he did it properly  .

[orabanda]

As usual, MG knows his stuff!
With the bronze properly tinned, the white metal will make a permanent bond.

What I didn't mention previously was that I had to remove the bush after line boring, remove the white metal and re pour it, because the crankshaft was tight to turn in places.

So, the first time the machining was done in a vertical borer. The LH crankcase half was bolted to my fixture, and the machinint clocked OFF THE CRANKCASE JOINTING FACE. After machining, the alignment was not perfect, because rotation was not easy.

I removed and repoured the bearing (as mentioned above), and insisted that the machinist set up off the LH (roller) bearing surface.

He then did the machining in a lathe, as mentioned at the strt, with perfect results.

This confirms what I have suspected for a long time; that the factory line boring of the crank case halves is not always at 90 degrees to the mating surfaces.
Richard

[manosound]

Richard,

Extremely interesting stuff. From the first story I took it that concentcity and angle-on-axis were both taken off the bearing outer ring in the left side. However, with this newly revealed story, I get it that he sought angle-on-axis from the mating surface but wonder what he tried for concentricity? I hope this question makes sense. Very convenient to have have a bell housing with a circular flange.

Richard L.

[orabanda]

Richard L,
For the first set-up, the machinist used the roller bearing housing for concentricity, but the crankcase jointing face for parallel. This is where it all turned to poo, because the bearing housing had been factory machined at a slight angle to the jointing face.

When set up in the lathe, it was easy to get it right. Concentricity was checked with a dial indicator, and the indicator was also used to check paralell ALONG the bearing housing. The angle was adjusted by shimming the base of the bellhousing in the 4 jaw chuck (and the usual judicious taps with the hammer!).

I used an old hydraulic pump - electric motor bellhousing for the crank case mount as there was one lying around, otherwise I would have made something similar, but probably half the length (not that it matters).

Dick from Oz

[manosound]

Richard,

Thanks for that explanation. I like having a clear understanding when the solution is brilliant.

Richard L.

[BSA_54A10]

A quick question: What assures the poured-in babbit adheres to the phosphor bronze?

Provided that you warm the outer first to prevent instant chill grains forming on the bronze then the Beta phase actually alloys with the copper and penetrates into the atomic lattice of the outer case.
As such it dose not adhere but , for want of a simpler term , melts into the case.
If you cut it in half there would be no clear sharp line that was yellow on one side and white on the other.

If done cold then you can get a suitation where the Beta phase solidifies out on the bronze case which starts to expand due to the heat from the molten metal which starts to contract due to its solidification and a mechanical tear occurs in the weaker material, namely the babbit but normally this only happens when you have a big lump of metal like pouring a babbit into the con rod on a long stroke A 7.

[bonny]

hi orabanda

couple of questions , where do you get the babbit metal ? did you make it yourself ? and do you have any pictures of the cases in the lathe ? it would be good to see. i was thinking about something similar making a jig for the milling machine and aligning everything off the roller bearing housing and using a boring head to bore the bush to size .

[BSA_54A10]

You can buy castable babbit ( in about 200 grades) from most engineering supply stores, usually in break offs.
It is not hard to make but use plenty of Potassium nitrate flux on top or you will burn off the lower melting point metals.
Ideally you would use a mix of 2 parts Potassium nitrate , 1 part ammonium nitrate & 1 part sodium nitrate but if you go and buy those 3 chemicals together expect a visit from the "hut, hut, hut" boys at about 2 am and they won't be riding their A10's.

[orabanda]

Hi Bonnie,
As Trevor pointed out, white metal is readily available.
I am using "OTL C.I.E., which is a tin base alloy, containing Cadmium.
It's application is " Compression Ignition Engines (Diesel) and all other types of internal combustion engines.

My machinist found it easier to set in the lathe rather than the mill, when it came to aligning along the length of the LH bearing bore. Setting concentricity is easy in either machine.
Richard

[bsa- bill]

You know I was chuffed the other day at my ability to machine ( grind with stone in my bench drill ) a head bolt so I could get a longer one to get past stripped threads in the head, then I read the above mails, boy oh boy the depth of expertise in here is something else.
Respect Richard