30 replies to this topic

[Wink Hackman]

Thanks Dale for these rollout charts.

Here is a 72 pitch version suitable for ISRA racing with wheel diameters in millimetres as well as imperial. I've scaled the numbers so that a 7/42 ratio on a 16.8mm tyre, which is a typical starting point, comes out at 1000.  Then you can easily see whether you're going slower or quicker with different combinations.  For me the immediate takeaway is that every one tooth change on the spur equates to a 0.4mm change of tyre diameter.  So 7/41 on a 16.4 tyre gives the exact same final runout as the 7/42 on a16.8mm tyre. But of course you might not be able to meet the minimum ground clearance on the smaller wheel, so I've added a row showing ground clearance for the ISRA minimum allowed axle height.

 

https://www.dropbox....Chart.xlsx?dl=0

 

[dalek]

Looks good.  Nice work!

[Mark Onofri]

A little late in my response but, I'm pretty sure we're on the same page. Your explanation is more refined. The smaller the pitch, the higher the possibility of a one time catastrophic stress overload. If not capable of handling the input ( and other factors)
Yes?

[Alan-E]

Dalek,

 

I would very much appreciate your making a chart with the following variables:

 

64P  

 

Pinions 12-15

 

Spurs 26-31

 

I attempted to make one screwed it up completely

[dalek]

Here it is, Alan.

 

 GEARING--TIRE DIAM. Rollout Chart, Flexi v2, 10-15,26-31,680-800-010r1.pdf   420.41KB   15 downloads

 GEARING--TIRE DIAM. Rollout Chart, Flexi v2, 10-15,26-31,680-800-010r1.xls   36KB   11 downloads

[Alan-E]

Here it is, Alan.

 

GEARING--TIRE DIAM. Rollout Chart, Flexi v2, 10-15,26-31,680-800-010r1.pdf

GEARING--TIRE DIAM. Rollout Chart, Flexi v2, 10-15,26-31,680-800-010r1.xls

GEARING--TIRE DIAM. Rollout Chart, Flexi v2, 10-15,26-31,680-800-010r1.gif

Thank you so much!! Have a nice weekend!