Posted by Colin on February 18, 2010 at 08:46:30:
I have tried to reply directly to your query but the title is too long and it gets rejected.( Bills?)
Here's my solution as I believe SP's is a bit too approx.
You can just expand the 34T gear and run it with the existing 26T gear but you must make sure that the 26T gear has not already been expanded and the 35T contracted. This is good practice to balance tooth strengths but is not always done. Check using the data below. I have assumed backlash figures.
Both gears are shown topped to maintain root clearance so you should top the 26T gear as shown. ( assuming that it is standard.
If the 26T gear is not standard, then let me know.
==================
Contact Ratio= 1.51
DP 5.00
Pressure angle 20.0000
Operating Pressure Angle 22.4422
Hob tip rad. 0.0000
Centre dist. 6.1000
Pinion
======
No.of teeth 26
AMC 0.0000
Addendum 0.2000
O/Dia. 5.5881
(O/D reduction) 0.0119
Root/dia. 4.7000
Hob Offset 0.0000
Total tooth depth 0.4440
Wheel
=====
No.of teeth 34
AMC 0.5305
Addendum 0.3061
0/Dia. 7.4003
(O/D reduction) 0.0119
Root dia. 6.5122
Hob Offset 0.1061
Total tooth depth 0.4440
Measuring data
==============
Min.total backlash .008
Max.total backlash .01
Fraction of b.lash on pinion .5
Pinion Hob/Cutter Offset for mean backlash = 0.0054
Wheel Hob/Cutter Offset for mean backlash = 0.0054
Pinion data:-
------------
Base tan.length over 3 Teeth 1.5449 / 1.5439
Dist.across 0.3456 Dia.pins 5.6708 / 5.6683
-----------
Wheel data:-
------------
Base tan.length over 5 TEETH 2.8207 / 2.8197
Dist.across 0.3456 Dia.pins 7.4488 / 7.4466