Helical Gears on a Standard Hobbing Machine

I have a Mikron 112 gear hobbing machine. It is designed for cutting spur gears only, not helicals.

There is just one simple gear train to set up the tooth count required, very similar to how a lathe leadscrew is set up for cutting threads.
A machine for cutting helical gears would also have a extra differential gear train to introduce the "lead" to the teeth as well as the tooth count.

My question is:-
Has anyone ever managed to work out a method of cutting helical gears on a simple machine by working out the gear train to suit the tooth count and lead combined in one ratio.
It sounds like it might be feasible, but probably end up with some very odd "un-gearable" set up.

I have a friend who is making a model petrol engine, and I would like to be able to cut him some pairs of spiral gears that run at 90° to one another with a 2:1 ratio in both left and right handed pairs.

I think this is a long shot, but over to you guys with more brain power than me.

Thanks
Phil

Okay, you have just stated your helix angle - its 45 degrees. Fairly extreme for a machine that cuts spurs only

The hob spindle will tilt over to 45° no problem, its the gearing I am struggling with.
Are you sure the helix angle will be 45°, I thought that would only apply if both the gears were the same number of teeth, I need a 2:1 ratio.

Phil

Just had a second thought about that, the helix angle will be the same unless the gear diameters have been adjusted maybe ?

Helix angle has to be same on both gears, regardless of their diameters. What changes is the LEAD required to make that helix angle on the different dias.

Gears at 90 degrees to each other are going to have a 45 degree helix.