Help with choosing right type of gear
Help with choosing right type of gear
(OP)
I have to detail a gear transmission in which positions and orientation of both gears were already chosen. I can't change axes angles beacuse some parts to which these gears are mounted were already made. Outer dimensions of gears are also fixed because of gear ratio.
I need help with choosing a right type of gears. I've attached a STEP file of gear pair. Maybe someone with more knowledge and experience with gear desigh will quickly see which type of gear should I use. I was thinking that I should use straight or spiral bevel gears. Crossed helical also came to mind but after closer look it looks like it has to be beveled.
Thanks for help in advance.
I need help with choosing a right type of gears. I've attached a STEP file of gear pair. Maybe someone with more knowledge and experience with gear desigh will quickly see which type of gear should I use. I was thinking that I should use straight or spiral bevel gears. Crossed helical also came to mind but after closer look it looks like it has to be beveled.
Thanks for help in advance.





RE: Help with choosing right type of gear
The correct terminology is 'beveloid'.
In your case you need a spur gear that meshes with a tapered helical.
The example below shows a set where the shaft angle is 10deg and the cone angle of the pinion is 7deg.
These gears are easy to manufacture. Most shops will do them, especially if they have CNC Hobbers.
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
Do you need another set, opposite hand, for the other engine?
Mike Halloran
Pembroke Pines, FL, USA
RE: Help with choosing right type of gear
Yes, I need a two pair of these sets, one is mirror. Need for this comes from using existing cylinder head for valves and new made crankcase. One more question. Can someone point me to some good (and practical) literature about these beveloid type of gears. Spur gear is not such a problem, but beveloid is new area for me. Maybe such literaure that shows calculation of gear geometry and also has some pointers about final drawings for gear production.
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
The examples below are from Audi & Porsche.
I've also seen these gears in stern-drives of boats and, would you believe, in the drive of a 1930's-built rotating platform for steam locomotives.
RE: Help with choosing right type of gear
https://en.wikipedia.org/wiki/Gear#Skew_gears
It will only have a point contact and therefore limited power transfer capability.
It is possible to make beveloids to have a decent contact pattern and power transmitting capability, but it is not easy. It used to be done with trial&error in the past with some success, but only the advent of Loaded Tooth Contact Analysis software has made it possible to design and develop the gears the gearcutter is showing us.
If you combine the two, you get all the issues combined, as well as some new issues...
If your application is a real world thing, you should be awared it won't be easy. Here is how it has been done with the beveloids:
http://www.geartechnology.com/issues/1105x/boerner...
RE: Help with choosing right type of gear
Good thing is that these gears don't transmit a lot of moment. But they can have large rpm.
I have to find the most simple solution that will also work (as always). But I have a lot of limitations that I have to consider, because as I already said a lot of parts for the engine were already made. Parts that define angle in this gear pair were also already produced.
I will check literature you provided and if someone gets any other idea, please let me know.
RE: Help with choosing right type of gear
Worse, it comes in pulses, as each individual cam lobe pushes its respective valve open.
Even worse than that, the valve tries to drive the cam forward as it closes, so the cam drive is subject to reversing torque. ... which is not real good for the gear teeth.
Do you have access to the original engine designer's calculations? There may be some hints therein that will save you from a few development dead ends.
Mike Halloran
Pembroke Pines, FL, USA
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
I just have rough design with gears shown as cylinders in CAD model. Except sprockets are shown more detailed. From this I have to detail it and make technical documentation.
I thought about some coupling also, but it would be hard to bring it in original design of drivetrain. Would have to change too many thing that I can't afford to change.
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
RE: Help with choosing right type of gear
Mike Halloran
Pembroke Pines, FL, USA