BMW R2 Bevel (Cardan) drive setup

[David Grenfell]

Hello
I am reassembling the bevel box for my R2 after replacing the damaged crown wheel and pinion.
Does anyone have any information regarding the assembly and setup of the backlash in the gears?
Hope you can help.
Regards
David

[David Grenfell]

[cwf]

You could try this :

You want the contact patch in the middle not to one side or the other.

Charlie.

[David Grenfell]

Hi Charlie,
Many thanks for the link. My R2 is a little more primitive, but the principles are the same. I was looking for some tech info regarding the backlash and shimming, but I may just have to wing it. I have been advised that 3-5 thousandths of an inch is what I should be aiming for!
I have a copy of the parts book, but there is no tech info.
David.

[4Taktix]

Hi David,
I must confess I'm not familiar with the particular R2 Specs.
So I can't tell, if the gears are "Klingelnberg" ( cyclo-palloid ) or "gleason" type.
However - I assume the appropriate backlash is similar to the later 250 cc models.
These were recommended 0,15 to 0,2 mm or 6 to 8 thousandths of an inch for the narrowest spot on the circumference
- valid for new gears.
The manuals and also the common recommendations explicitely say, that a correct contact-pattern is way more important
than the correct backlash, by all means.
So for e.g. used Klingelnberg-gears there is no chance to adjust wear by reducing the backlash.
This isn't possible due to the particular Klingelnberg-design.
So it is highly recommended to rather tolerate much backlash but have a reasonably contact pattern,
then to have a backlash within specs but a "bad" contact pattern.
Absolutely worst case is, to have to little backlash ! This is a NO-GO !
This is valid for Klingelnberg as well as for Gleason type.

Regards,
Sascha

[cwf]

Can you give us a photo or two?

[David Grenfell]

Hi David,
I must confess I'm not familiar with the particular R2 Specs.
So I can't tell, if the gears are "Klingelnberg" ( cyclo-palloid ) or "gleason" type.
However - I assume the appropriate backlash is similar to the later 250 cc models.
These were recommended 0,15 to 0,2 mm or 6 to 8 thousandths of an inch for the narrowest spot on the circumference
- valid for new gears.
The manuals and also the common recommendations explicitely say, that a correct contact-pattern is way more important
than the correct backlash, by all means.
So for e.g. used Klingelnberg-gears there is no chance to adjust wear by reducing the backlash.
This isn't possible due to the particular Klingelnberg-design.
So it is highly recommended to rather tolerate much backlash but have a reasonably contact pattern,
then to have a backlash within specs but a "bad" contact pattern.
Absolutely worst case is, to have to little backlash ! This is a NO-GO !
This is valid for Klingelnberg as well as for Gleason type.

Regards,
Sascha

Hi Sacha, thanks for the information. I do not understand the difference between Klingelnberg and Gleeson type gears!
The original crown wheel and pinion were damaged when I purchased the bike, and I gave had reproductions made. The engineer who made them for me said he had checked the contact pattern, and to assemble with 3 -5 thou backlash.
On first asembly I have over 20 thou! It seems that I need to shim the crown wheel as the pinion position is determined by the dual race bearing.
Any thoughts?
Best regards
David

[4Taktix]

Hi David,
only the engineer who reproduced your gears will know the type.
I suppose it will be different from the original gears, it depends on the geometry and capability of the
machines used. Concerning the shimming - I don't know the setup possibilities of the original R2-Drive.
But in general, shimming the crown-wheel mainly has an effect on backlash and just slightly on contact-pattern.
Shimming the pinion mainly has an effect on Contact-pattern, and only minor to backlash.
But probably you can't change only one of both, without influencing the other.
Here's a clip, which helps understanding the interrelation. (but not necessarily valid for "Klingelnberg")

On my R25/3 Reardrive, both can be adjusted by shim washers on the bottom of bearing seats.
For some spots you have to buy the expensive washers, designated particular for BMW Rear drive,
in other spots you can use standardized shim-washers, available in many sizes and thicknesses and rather cheap.

Regards,
Sascha

[David Grenfell]

Hi David,
only the engineer who reproduced your gears will know the type.
I suppose it will be different from the original gears, it depends on the geometry and capability of the
machines used. Concerning the shimming - I don't know the setup possibilities of the original R2-Drive.
But in general, shimming the crown-wheel mainly has an effect on backlash and just slightly on contact-pattern.
Shimming the pinion mainly has an effect on Contact-pattern, and only minor to backlash.
But probably you can't change only one of both, without influencing the other.
Here's a clip, which helps understanding the interrelation. (but not necessarily valid for "Klingelnberg")

On my R25/3 Reardrive, both can be adjusted by shim washers on the bottom of bearing seats.
For some spots you have to buy the expensive washers, designated particular for BMW Rear drive,
in other spots you can use standardized shim-washers, available in many sizes and thicknesses and rather cheap.

Regards,
Sascha

Hi Sascha,
Thanks for the advice. I have ordered some standard shimms for the crown wheel and will have wait for them to arrive before having another go at it.
Youtube video is interseting. Thanks.
Regards
David

[cwf]

Hello David,

I'm going to Weterama in Lodz, Poland beginning of May, in case you need anything not too heavy.

Charlie.