Cardan shaft angles

[Mad_Dan_Eccles]

Folks

 

I have a question about miniature Cardan shafts of the type used in OO and HO diesels. I am working on a small single Fairle in 16.5mm gauge,. One of the featurs of this particular design is very short side tanks which means that a convential drive to a gearbox on the driven axles is going to be in full view and will rather kill any semblance of realism . 

 

Turning the motor round  and mointing it in the firebox so the ouput shaft is at the rear,  dirving to a  reduction gearbox and cardan shaft to drive a low profile final drive works very well in hiding the works - a couple fo millimters of the of shaft will be still visible to the sort of people who like to inspect models with dentist's mirrors. However the final drive has to be to the rear axle of the engine bogie as the bogie pivot is almost on top of the middle axle. which means the worm end of the shaft will be at the worst place for side to side deflection on tight curves.    Sketh attached in roughly to scale but shoudbe regarded as nore tha a diagram tio show the layout

 

I have never used this sort of drive other than in RTR form and am concerned that the throw at the rear of the bogie and the short lenth are going to cause issues.  I am looking at about a 7 degree angle at both ends of the shaft on a 500mm radius curve and the distance beween the centres of the UJs works out about 16mm with the wheels all pointing in a strait line.  In a full sixe kight duty application I would usually be fine with these at speeds up to about 1500-1800rpm but with a 14:1 final drive the shaft will be turning at nearer 3500-4000rpm.   Not knowing how these things scale is this angle is likely to be a problem?  Most diesel drives have much longer shafts and are have the UJ closer to the pivot piont on the bogie an I dont have any refercne to deal with such small drives

 

 

[6959]

Full size data.

 

https://spicerparts.com/calculators/driveline-operating-angle-calculator

[cheesysmith]

Check out branchlines. I picked up from them at Warley last year a extendable drive shaft with universal joints on each end.