Author Topic: Motor strip  (Read 5518 times)

Online duTch

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Re: Motor strip
« Reply #75 on: 06.04. 2018 06:48 »

   That NU206 EM C3 roller bearing of Servodyne's looks interesting-
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
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Offline olev

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Re: Motor strip
« Reply #76 on: 06.04. 2018 09:17 »
No doubt dynamic balancing is a great idea.
It would be better yet if someone could come up with the factory blueprint balance factors for an A7 and an A10.
The bloke doing the balancing will want a number.
As a matter of interest, Glen what did he use on your Vincent.
cheers

Offline Sluggo

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Re: Motor strip
« Reply #77 on: 06.04. 2018 09:55 »
My $0.02 on balance numbers, Dont get hung up on it except learn what many others are using, but its not as fixed as people think.

My guy does motorcycles on the side because he likes them and enjoys it. (E.V. Lewis Dynamic Balancing) But his main job is airplane propellers and industrial equipment either of which can kill people if done wrong.

Ernie talks to me about what I want and the application,  #1) is what kind of suspension and mounting? IE : rubber mount or fixed and type of frame  #2) What RPMS do you typically see and use the bike in?

Rocking couple is a specific issue, but even perfectly blueprinted, any vertical twins gonna vibrate to some degree so what Ernie does is push the bad vibe range to an RPM you dont use much.  I can tolerate some vibs at Idle but most vintage bikes I build I set the goals as stay under 5000 RPM because with a  50 year old bike unless you are going to re-engineer the whole motor with a new EN40 billet crank, New Carillo rods, forged pistons and modern Beehive springs and Stainless valves you have zero business revving past that.
Gear it accordingly.(CS or Rear drive sprockets usually)

So Ernie writes out all the specs and weights so if you have to replace parts you simply target those weights .But I never dictate to him I want 52% or any such thing.  Maybe other shops are different,
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Offline tlmark

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Re: Motor strip
« Reply #78 on: 06.04. 2018 12:57 »
Unfortunately, I won't be having it balanced I would have like too but she is over budget really and the quote I had was silly money as far as I was concerned.

Maybe I regret that bit of penny-pinching later but for now, I want it back together.  :!

Offline worntorn

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Re: Motor strip
« Reply #79 on: 06.04. 2018 13:16 »
No doubt dynamic balancing is a great idea.
It would be better yet if someone could come up with the factory blueprint balance factors for an A7 and an A10.
The bloke doing the balancing will want a number.
As a matter of interest, Glen what did he use on your Vincent.
cheers

We used 60% wet, which is what the crank builder had claimed the crank was built at.
This is a custom crank, porkchop style and  built with oversized mainshafts and big pin for high rpm.
We found that the bf was way out, close to 90 % . This called for removal of approximately 3/4 of a lb of material opposite the big pin. The balancer also found a 22 gram side to side discrepancy which he corrected ( rocking couple).
I asked for smooth at 4 k but it seems smooth right to 7 k in the intermediate gears. Haven't had it past 5 k in top and probably won't unless on a track or at Bonneville. Not crazy about the salt damage that can occur at Bonneville.

Glen

Offline PatM20

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Re: Motor strip
« Reply #80 on: 06.04. 2018 14:17 »
Hi Servodyne,

Why choose the NU206?

Was the one you took out a C3 fit too?

Doing mine soon, so was interested in why you chose one versus the other.

Regards

Pat

Offline Servodyne

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Re: Motor strip
« Reply #81 on: 06.04. 2018 19:06 »
Hi Pat

The NF206 bearing that I took out of my A10 didn't have any markings to suggest it was a C3, therefore I suspected it was a CN.
Also, although it was made by NSK, in Japan it didn't look very substantial with only 7.5mm wide rollers, compared with main bearings from other 650cc twins such as Triumph, Norton or A65s.
The NU206 in comparison is a high capacity bearing with much wider rollers and a brass cage which I prefer over a pressed steel one. Of course the proof is how long it will actually last in service.
I'm with everybody else on the subject of dynamic balancing. The only reason I didn't have the A10 balanced, was that I'd just had a Norton 650SS and an Atlas done at Basset Down and my wallet had taken a bit of a beating. It turned out ok though but it was more good luck than good management.

Regards

Jim
1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando

Offline worntorn

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Re: Motor strip
« Reply #82 on: 06.04. 2018 20:24 »
Jim, how did the 650ss and Atlas fare with the Dynamic Balance?

Glen

Offline olev

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Re: Motor strip
« Reply #83 on: 07.04. 2018 05:33 »
A few years ago I checked out what was involved in getting the crank of a 350 matchy single balanced.
No one would touch it without being given a balance factor.
They were quite happy to guarantee their work but refused to take responsibility for the result.
I'd be pretty suspicious of an *expert* who would balance a standard crank without explaining what the specs were.
Balancing is an exact science. selecting a balance factor isn't.
If you get it wrong you have spent money on a pig.
Sluggo, can you ask your mate Ernie what BFs he would use on standard A7 and A10 plunger and swinging arm motors.
Without wishing to offend anyone I'll bet you can't get a straight answer.
cheers

Offline worntorn

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Re: Motor strip
« Reply #84 on: 07.04. 2018 05:58 »
Part of the problem is that there seems to be more than one equation floating around out there.
The company that builds the most Dynamic balancing machines, Hines, has a simple equation that appears to be the most widely used. It is not universal, hence the wildly disparate " ideal" bf numbers for any given engine type.

Glen

Offline Sluggo

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Re: Motor strip
« Reply #85 on: 07.04. 2018 06:38 »
Olev, Singles are a different beast to balance and there is a lot of other factors involved in what you want it to do.  I called Ernie last fall and asked his opinions on singles and he has done them, But we could get into specifics because until he has the parts in hand it is difficult to speculate.

*One point for clarification for those looking at this.  There is blueprinting which is optimizing all the specs, as well as correcting dimensions to the optimum. Some people get REALLY offended when discussing this, but production for any product is done to a std and that can vary widely. Some vintage bikes, especially ones made by companies in financial distress can turn out parts with significant faults or flaws. The Matchless center bearings are a prime example. Brilliant idea but many were misaligned, once corrected or "Blueprinted" they work great. 

Balancing takes 2 steps. First is optimizing specs such as modern repop pistons (JCC, EMGO and other Asian pistons for Brit Iron are excellent and 99% of the time spot on in measurements, But I did have one exception recently, But the pins can vary widely in weights.  Conversely Old Hepolites varied to the extreme in measurements and weights).  So the same with rods, and any other part. You get them to a comparable weight.  Then you start doing the math.
At this point you CAN static balance it, and thats better than nothing and some talented people can do this in their home workshop, My old friend Sir Eddy used to do that to all his builds.   But a static balance can only get you part way.
For a metaphor or comparison if any of you recall the old static bubble tire balancers many gas stations used to use.  Thats basically a static balance.  But modern Tire shops now mount up on a machine that spins the wheel & tire and identifies a number of issues.  Dynamic does that and more.  But you CANNOT check for rocking couple by a static balance.  It only shows up when being spun and sensitive instruments pick it up.
extreme rocking couple will rattle your teeth out and blur your vision.

Now, as far as what a BSA might be, Ernie knows the balance figures and can quote percentages but shys away from it because it varies widely.  One is, I know for a fact that some BSA cranks for A10s can vary as I have weighed a few,. plus there seems to be a variable in type and part number and I spent a lot of time on this site and Britbike looking at different unit and preunit cranks,  (Very confusing)  So, while I cannot say conclusively for all BSA A10 & A7 cranks, I can say the Unit A65s were all over the place. We did several including some experiments with lightened and balanced cranks.  I have some NOS BSA Flywheels and they made several different flywheels and they balance differently not just in weight but some disparities even in the same part numbers.   

**I had an old flat tracker and MX racer known as "Capt Dirt" and he used to build a lot of racebikes and once told me the BSA unit twins were superior in many ways, but their cranks were too heavy. He told me to look up the lightest Triumph 650 crank (1966 IIRC) and make the A65 Crank the same.   Not easy, about a 4 lb difference IIRC (I have notes I would have to consult to give exact specs).  To get down to that, we had a lot of machining and to balance we had to add mallory to get it to work.   Not the optimum street bike but it was VERY fast and revved and spun up like a 2 stroke.  It was a super fun hooligan bike but not what you would want for lazy back road toodling about.

So, yes, Long story short, I could get you some approx balance factors but there is too many variables to say exactly why, And before I forget again.. Most repop pistons for BSA twins seem to be quite a bit heavier, and that can skew your numbers.  I will be looking at that again when I build my 68 Spitfire.
Remember that any advice received on a free internet forum is generally worth about 1/2 of what you paid for it.
We overcharge every 3rd customer to pass the savings onto you.
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Online groily

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Re: Motor strip
« Reply #86 on: 07.04. 2018 08:07 »
Dunno if the attached will attach - but for anyone interested and who understands these things (I don't really) here are some data sheets from a crank I had dynamically balanced a while back. Regardless of my lack of comprehension of precisely how and what, the result was good at the 61% stated. Very smooth engine in this case (crank with centre main bearing on the AMC twins of course). I thought most As were done to about 55%. But IKBA  - I had it done because it was a brand new crankshaft so I had no idea what it would be like if not given some serious attention.
Bill

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Re: Motor strip
« Reply #87 on: 07.04. 2018 08:12 »
Oops - the main data sheet too big to attach - sorry.
Bill

Offline Servodyne

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Re: Motor strip
« Reply #88 on: 07.04. 2018 09:39 »
Jim, how did the 650ss and Atlas fare with the Dynamic Balance?

Glen

Hi Glen.

I'm still in the process of re-building the 650SS, but it's got to be better than it was. I used to get blurred vision around 50 or 60mph.

Another project is an A70 which I'm having to use an A10 crank modified to fit. The crank's currently at SRM being balanced, so it's going to be very interesting to see how that turns out. I didn't use Basset down for that one as they didn't even know what an A70 was.

Jim 
1957 BSA A10 Spitfire
1971 BSA A65 Firebird
1971 BSA A70 Lightning
1975 Norton Commando

Online duTch

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Re: Motor strip
« Reply #89 on: 07.04. 2018 11:00 »
Quote
....... but not what you would want for lazy back road toodling about.   ......

 ...So we can add that to 'tootllng' and 'pootling'    *conf2*

 
Quote
Dunno if the attached will attach -....
   I think that's well appropriated oxymoron... *smile*

 ok Saturday night- maybe I should go antisocialise elsewhere...  *bash*

 Re 'Balancing' I still have to justify my balance act to the Kiwi...haven't forgotten, 'work in progress'.... *beer*
Started building in about 1977/8 a on average '52 A10 -built from bits 'n pieces never resto intended -maybe 'personalised'
Have a '74 850T Moto Guzzi since '92-best thing I ever bought doesn't need a kickstart 'cos it bump starts sooooooooo(mostly) easy
Australia