R1200S - Another little "bling" with impact

[Sofatester]

Just look at the pics. Though I'm not revealing all, I guess they are self-explaining. Wonderful impact. Plus 2 hp (DIN). Although it was quite some work and harder than expected. But with a little help from two friends........

[ergomoto]

I'm afraid the omitted key word here though is "R1200S" and not R1100S(?). Beautiful bits non the less.

[turboflyer]

Belt drive out of Titanium?

[Sofatester]

Originally Posted by ergomoto

I'm afraid the omitted key word here though is "R1200S" and not R1100S(?). Beautiful bits non the less.

You're right, sorry. I just edited the headline.

[Sofatester]

Originally Posted by turboflyer

Belt drive out of Titanium?

No, not that expensive. I don't like Titanium, though. Too expensive and more difficult to work with. What you see is a combination of Nippon Denso steel and 7075-T6 Alu (7075 alloy was first used in mass production in the mid-30's of the last century by Sumitomo, it was a key factor for the superiority of the lightweight and fast accelerating early Zero fighter planes that were constructed and built by Mitsubishi).

In this case it's rather the idea, the performed work and the impact, not the material.

And the radial free play is not awful 0,05mm as stock but now between 0,006 and 0,01mm.
There are so many possibilities to improve a bike if you just look, measure and think....

[markjenn]

Though I'm not revealing all, I guess they are self-explaining.

Ah, no they are not. I'd feel more like congratulating you for good work if I knew what you had made.

- Mark

[ergomoto]

But, I guess in this regard, both motors share the same basic design features and in particular these belt pulleys. Crazy joining of dissimilar metals and fabrication. So the deal here was spun weight savings? Always fun to hear about something new to look into...

Mark S

[ckcarr]

Originally Posted by markjenn

Ah, no they are not.

- Mark

Aren't they geegaws?

[GotRoad?]

I'm game..they're some sort of spacer for that nut (which is really ugly & ought to be replaced). I I remember some talk about engineering a race for a needle bearing or some-such gee-gaw, so my guess that this item is on the receiving end of same.

[AZ-Twin]

Underdrive pulley? Makes the alternator spin slower thus reducing power loss to drive the alternator?

[PFFOG]

Originally Posted by AZ-Twin

Underdrive pulley? Makes the alternator spin slower thus reducing power loss to drive the alternator?

My bet is on your answer. For those that don't putter around town, makes perfect sense. And if sofa spends any quality time in the Alps, he is in2nd and 3rd a lot.

[ergomoto]

Why would you need exotic multi combination alloys for that? You could just lath up different sized pulleys out of one material. Though there may be a more optimal speed to turn the alternator, wouldn't more be gained by the motor spinning less weight -baring ditching the alternator altogether track style?

Mark S

[shreddr]

here's the SJBMW version, stock in the rear at 1.5:1 drive, underdrive units in front at 0.9:1



San Jose BMW - Parts

[ergomoto]

Are the pulleys billet just because their too cool not to spool? Sorry.
Mark S

[Sofatester]

Originally Posted by AZ-Twin

Underdrive pulley? Makes the alternator spin slower thus reducing power loss to drive the alternator?

Perfect answer.

shreddr was also right, pointing out to the SJBMW parts.
I didn't know they had some in stock but they got nearly the same result. Transmission ratio stock is 1,5 (crankshaft pulley) to 1 (alternator pulley) as shreddr said.

Now it's 0,88 to 1 on my bike.

And nobody knows, how much work was done by SJBMW before the first pulley was made. I know, now , because I had to do the same work.
As we say in germany: "the devil hides in the details".

The combination of steel and an appropriate alu is easy to explain:
It's too much work to machine (lathe) the exact profile for the belt ribs out of the full material if you haven't CNC. The steel of the stock pulleys is also more rugged. If you search all the stock alternator pulley parts of the BMW world, you'll find a matching stock pulley as a good start on the new crankshaft pulley. I was lucky, a friend of mine supplied me with the right small pulley 2nd hand for just a few €.
And using steel for the inner parts would make the pulleys too heavy. You also get more safety by using appropriate alu because it's a shrink fit secured by 3 pins made of a different alloy (also shrink fit, watch the pics). If the parts get warm the alu grows bigger than the steel, ensuring a tight fit under all circumstances outside the pole regions and siberia, Alaska or the Hudsonbay territories (I guess even there but anyway, I won't test that).

The downside of this mod is a lower power output from the alternator. Becomes even more delicate when using small batteries like my hawker odyssey PC 310.
You need more revs for the same current output, using heated grips together with the lights when driving in the city or under 4000 rpm becomes a problem. PFFOG was right on that, too.
That's why the factory didn't do that. On the other hand, the alternator doesn't have to work so much after the mod.
8800 rpm on the crankshaft are 13200 rpm on the alternator shaft using stock pulleys.

Now it's only 7744 rpm on the alternator shaft when revving 8800 rpm on the crankshaft.

[turboflyer]

So what would be the trade off in pulley wear verse belt wear. Aluminum pulleys would seem to wear quicker but be easier on the belt. But the steel pulley would last longer. Although longer might be 300,000 verses 250,000 miles, dont know. And the actual HP gain at redline or cruise is? Have considered the set up. Just not sure it is cost effective for a non-track bike.

[Sofatester]

Don't think about wear. Surely, an alu pulley will have more wear than a steel pulley, but you can't say that this leads to less wear on the Poly-V-belt.

If the alu pulleys do have wear , then the fine abrasion (wear) of that alu is like emery to the belt.

So I won't bet on a longer belt life when using alu pulleys !

Besides, BMW demands the change of the poly-V-belt every 40,000 km (25,000 mls).
Don't disregard that !

In former times (R1100S) the interval for changing the belt was 60,000 km (40,000 mls) but then many failures (ruptures, spring-off or sliding belt) occured, so the interval was shortened to 40,000 km (25,000 mls). That changing interval should be obeyed in any case even if the belt looks good.
A new belt is quite cheap, though.
Use only quality belts such from Conti or Gates e.g..

Mentionable power output improvement ( > 0.5 hp) is achieved from 3,500 - 8,500,
+2.2 HP (DIN !) is the peak of the improvement roughly between 5,000 and 7,500 rpm.

I won't do that mod on a bike which isn't used on track and which is mainly used in cities (traffic jam, slow speeds and revs) , except when it's a bike without ABS and without heated grips. But that's just my personal 23c.

[turboflyer]

"The fine abrasion (wear) of that alu is like emery to the belt. "
Good to know. I was thinking of asking a machinist friend of mine to make a set of idler pulleys for my Ducati from aluminum. May have to re-think that one. It will be interesting to see what he says if I ask him to make them from titanium or beryllium.

[Sofatester]

Titanium is sharp. Needs good machining. And I never worked with beryllium. (only as an ingredient of some alloys)
All I said was that alu pulleys don't lead to a longer "belt life" just because they might have a bit more wear than a steel pulley.

That doesn't mean the belt will be used up in a shorter time.

Out of experience of others I'd guess it will be about the same compared to the stock parts made of steel, as long as the quality of the aftermarket alu pulleys is at least equal compared to the stock parts. Just as I said: Don't think about wear (if the quality of the pulleys is good).

Besides: The SJBMW products in particular have a good reputation as far as I know.

As I said: BMW demands the change of the poly-V-belt every 40,000 km (25,000 mls). That also means you are to change the belt within this interval even when using stock parts.

That's all.

Ducati belts are something totally different. Ducs are not fitted with poly-V-belts (are they ?), but they do have belts with thick lateral ribs. The pulleys are totally different, too. (cam drive) I can tell because I owned a 750-F1 years ago.

[RoLoo]

Originally Posted by Sofatester

As we say in german: "the devil hides in the details".

...weird..., because the last time I visited Germany ; the Germans spoke German...






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