24 HORAS STILL ALIVE

[JPALOMO]

Sorry for the delay, I'm not sure how many years without writing you, but i'm here again. I start making somme modifications in a spanish Ducati 24H using the crankshaft of 66 mm stroke, used by spanish 250 cc, with a 76 mm piston, then I have about 300 cc. The problem was the top bevel shaft because I use a head from a italian Ducati, 74mm bore, and the top bevel shaft need to be 8 mm longer. I make an unprofessional modification welding some steel at the end of the shaft, but now I have a new shaft with the length I need, 171 mm from the gear to the end...I'm at the end of the way. I need to know which kind of bearings I need for the camshaft, ¿Angular contact? ¿Do you have the code? Thanks in advance.
Juan Palomo

[Jordan]

Try:
For the top, self-aligning bearing 1202, ID=15 x OD=35 x Thickness=11
For the bottom 2, angular contact bearings 7202, same dimensions as above.

Jordan

[JPALOMO]

Thank you Jordan, what about the camshaft bearings? Also I will make the test with the screwdriver and a piece of rubber to know the lateral clearance of the crankshaft, las time I make the test I was no sure if the clearance is between the crankshaft and the main bearings or was the proper bearings clearance, how can I discriminate it?
Thanks again,
Juan

[Jordan]

Camshaft bearings 6202, same nominal size as the cardan shaft bearings.
I don't think you should have any measurable clearance between crankshaft and main bearing inner races, even with worn bearings.
End play should be checked and adjusted, especially if a new centre gasket is fitted. A steel plate screwed to the crankcase outer face allows a magnetic base dial test indicator to be simply employed.
How do you test with rubber and screwdriver?

Jordan

[DewCatTea-Bob]

[quote= JPALOMO ...
" Sorry for the delay, I'm not sure how many years without writing you, "

____ Here's a link to your last-thread on this same topic... viewtopic.php?f=3&t=40&p=159#p159


" but i'm here again. "

____ It's been a LONG-wait, Juan ! _ I'm very-glad to learn that you haven't given-up on your somewhat unique motor-project !



" I start making somme modifications in a spanish Ducati 24H using the crankshaft of 66 mm stroke, used by spanish 250 cc, with a 76 mm piston, then I have about 300 cc. "

____ As you ought-to recall, this 76x66mm B&S engine-project had long-been an intended project of my-own, and I had all the motor-parts (to complete the 300cc-motor) EXCEPT-for one of the 66mm-stroke crankshafts !
__ This special-project was one I had really wanted to get done because I always thought it would be great to have a close-example of the 300GT-motor that Berliner had asked Ducati to produce back around 1962, (which much-later became the 1965-350Sebring, instead) !



" The problem was the top bevel shaft
and the top bevel shaft need to be 8 mm longer. I make an unprofessional modification welding some steel at the end of the shaft, "

____ You really should've kept in contact with ME concerning THIS-project ! _ Cuz there's probably nobody-else in the-world who has been atop-of this particular motor-project,, cuz-as for one-thing, I've already had that particular tower-shaft length-issue all worked-out decades-ago (back in 1978) ! ...
All you really needed to get for the job, is the upper tower-shaft employed for 350Sebring-engines or 250w-c.engines,, then cut-down it's tip-end 3.5 to 4mm, (as well as roughly the same-amount off-from the tip-end of the lower tower-shaft & shaft connector-sleeve, too). _ (This grinding-job is easily done with an automotive-type tappet-grinder, and any amount removed [from the shaft-tips] between 3.5 & 4mm will be sufficient,, however the con.sleeve's length-height really needs to-be cut-down 4 to 4.5mm !)


" the top bevel shaft need to be 8 mm longer "

____ Why exactly do you think that ? _ Do you mean "8 mm longer" than a standard n-c.250's 'upper tower-shaft', or, 8mm taller than a 200-based Mototrans-250's 'upper tower-shaft' ?
__ Maybe I should need to know whether your particular 300-project's 'bottom-end' is based-upon a standard-Italian n-c.250 or actually upon a '200-based 250-Mototrans' bottom-end version. _ As I'm really not-SURE if the later-version has a con.rod-length that's any-different than that of a std.n-c.250 .
However if both bottom-end versions actually do employ the very-same dimensions in all these regards (as I've assumed), (or you're actually employing a std.n-c.250 bottom-end),, then, you ought-to have realized that the 8mm-difference in stroke, is actually cut by HALF, (for the height-area above the crankshaft's center-line)... So-thus the top-end height-difference is ONLY (about) 4mm, (due-to the crankshaft-RADIUS difference, [rather than the stroke-difference] ) !
__ So bottom-line... ¿ Are you still sure that your upper tower-shaft actually has to-be fully "8" mm taller ?



" now I have a new shaft with the length I need, 171 mm from the gear to the end... "

____ Where did you get THAT tower-shaft from ?
__ It would be of fair interest to see any pix of your various tower-shafts (placed aligned side-by-side), which have been considered for this project !
____ You haven't mentioned how you've solved the cyl.jug-height issue, (which also needs to-be adjusted as-well!). _ ¿ Are you going to employ a 250 or 350 cyl.jug ?
__ I know that Ducati's-own 300-proto.motor employed an eight-finned 250-jug with an extra 4mm added-to the thickness of the base-flange of the cyl.jug. _ So you COULD possibly rather add four of the optional 1mm aluminum-spacers, (which is what I-myself had originally planned). _ Or-else you could possibly employ a 350-cyl.jug with 4.5mm milled-off from the bottom of it's base-flange.



" because I use a head from a italian Ducati, 74mm bore, "

____ Yes, as any 250/350 cyl.head of the 74/76mm bore-size type, will work !



" I need to know which kind of bearings I need for the camshaft, ¿Do you have the code? "

____ Those two camshaft-support ball-bearings were originally the common std.type of such (plain/bare) support-bearings -(code-#6202),,
(however, the case has been made for substituting those ordinary/original-type ball-bearings with the same self-aligning type as is employed at the top of the upper tower-shaft -[D.part-# 75243.1542] ).
Both bearing-types are of the very-same dimensions -(15/35/11mm, as Jordan has already listed) !


Duc.project-CHEERS,
D.Bob

[JPALOMO]

Sorry for not answer yesterday, I will try to answer to everything, now I'm on a hurry, but think that the the engine is a genuine spanish 24 horas, I will prepare somme pictures but it will be next week. Also if you are interested in a crankshaft 66 mm stroke, I can find here for you.
Regards, Juan

[DewCatTea-Bob]

[quote= JPALOMO...
" Sorry for not answer yesterday,
now I'm on a hurry,
I will prepare somme pictures but it will be next week. "

____ Well after the long-wait we've had, another few days shouldn't hurt too-much.


" but think that the the engine is a genuine spanish 24 horas, "

____ Hopefully Eldert or someone will offer their related knowledge of this stuff,
cuz I had thought that the '24 Horas' employs the smaller/square bolt-pattern of the 175/200-motor !?



" Also if you are interested in a crankshaft 66 mm stroke, I can find here for you."

____ I still would've been quite-interested in such a crankshaft BUT,, the 4-speed/250-motor bottom-end which I HAD left for this old-project, got stolen (along-with a few others) from my home ! _ And-so now any thought of ever completing a 300Duke-motor of my-own, has been DASHED-OUT !


Sad-Tears,
-Bob