crankshaft tap - flywheel H3

[douglas1947]

Hi,
I have worked and measured on the crank tap + flywheel hole last week.
I have decided to "refresh" the surface of the cone (crank shaft) on the lathe and make a new bush for the flywheel.

I would like to know the original the length of the 30mm dia part (from crank hub to beginning of cone - on my crank 35mm length).
I´m not shure, if the 35mm are original length, because the surface of the cone seems not to be the original.
There could be complications with the clutch mechanism, when I do a mistake.

I hope someone can help.

Michael

[hoejmark]

Hi Michael
I measure the length to be 31 mm.
/Soren

[douglas1947]

Hi Sören,

thanks for sending the photo and measure of the tap.
The cone on my tap seems to be not exactly round, also on the thick end.
I´m not shure about my possibilities to realize a solid repair.
But would you please send me the dia on the small end of the cone?

Michael

[Doug]

Michael,

Don't go by the length of the taper to determine the angle, it will not be accurate enough. Douglas specified the taper as 10 degrees included, or 5 degrees per side. The taper in the flywheel has a big end diameter of 0.982 (25mm). The length of the taper in the flywheel is 1-7/32 inches. So as long as the taper on the crankshaft is less than that, the nut will screw up tight.

The length of the 25mm journal (as measured by Soren) will set the distance of the flywheel away from the crankcase. This does not have to be very precise, as you do have some latitude with the clutch adjustment mechanism. Also shims between the main bearing and the crankcase (to set the crankshaft end-float) will alter this distance slightly.

-Doug


[fix typo. 26Feb18]

[douglas1947]

Hi Doug,

thanks for your reply, but the measurements you are sending makes me confuse.
The crankshaft of these engines (B29, H3, B31) have a crank dia on drive side of 30mm, so the big end of the cone has 300mm and the thin end may be have around 25mm (on my shaft the surface is destroyed, specally on thin end).

I have 2 flywheels, the worn one with brass center and a good one  with 29,5 to 24,0 cone of 33,5mm length.
Both have the shape of the flywheel of my S6 (with cylindrical edges).

I hope these types are the right flywheels for the engine?!
My be I can "clean up" the cone on the worn crank shaft to fit to the good flywheel, there is now some space to the 31mm Sören had measured.

Is it necessary or usefull to press out the center?
(I have no big lathe to fit the flywheel.

Michael

[Doug]

Michael,

My mistake, I was assuming it had the 25mm timing side journal like the earlier 350cc engines. The numbers I used came from some info for a D29, which probably are the same as the 350EW.

If it has the 30mm journal of the later engines, then can offer the following numbers. Crankshaft: length of journal: 1.25", length of taper 1.281, angle included 10 degrees (5 degrees per side.) These dimension apply to the S6 through the Blue Chief at minimum. Flywheel: big end diameter 1.150", length 1-19/32, angle 10 degrees included (5 degrees per side.) This based on a Blue Chief flywheel, but the numbers ought to be good backwards to the S6 era.

Generally, the 'Colonial' models had a heavier flywheel, identical to the standard flywheel but with a half inch larger diameter. I do not have a picture showing what the correct flywheel looks like, but would have thought it used the style with the rounded edge (i.e. not the cylindrical edge like the S6.)

-Doug


[fix typo.  26Feb18]

[hoejmark]

Hi Michael
I agree on the figures Doug give now.
My H3 flywheel has the square shoulders and an outside diameter of 235 mm. The big end taper is slightly below 30 mm.
When flywheel on the crankshaft, I can measure a distance of ca. 34,5 mm from shoulder of the crankshaft to the flywheel hub.
Regards
Soren

[douglas1947]

Hi Doug and Sören,

many thanks for the last measures, so I see clearly now!

Also thanks for the good photos, I see I have the same type of flywheel and the distance is right to what my crankshaft should have to the flywheel.

Is the conical bush in the flywheel cylindrical /from what sidepressed in?

Michael

[hoejmark]

Hi Michael
There is no bush pressed into the flywheel. The flywheel is made out og one piece.
From the photo it may look like a bush, but it is only a slight wear on the face of the hub.
Soren

[douglas1947]

Hi Sören,

thanks for the information.
So I have learned again!
My 2nd "good" flywheel has defenitly also a bush (too wide on the small end of the cone to fit to the crankshaft)!
So may be, also modified?

Michael

[douglas1947]

The "good" flywheel.

Michael

[Doug]

Michael,

Douglas did not bush the flywheels from new. Any that have a bush are repairs. Given that scored and torn tapers on crankshafts was a perennial problem with Douglases, they have been a lot of machines out there that were/are in need of repair!

-Doug

[douglas1947]

Doug,

thanks for the information!

Michael