worm gear box

To much end play in the driven, and clearence in worm and drive, load passing inertia to drive shaft which will momentry drive the driven?

a.k.a. backlash

Do u mean that the CTC distance between the worm & worm gear is more than required or any of then is not cut to the given dimensions creating more backlash or both?

No refering to the thrust from the drive to the driven (turnuing moment plus axial thrust). if the load is high the axial loading could cause a sideways movement of the driven to impart a driving force to the worm drive (initially), this was just an observation, there appears to be plenty of good advice after my post. I assume there was good reason for you to design the worm drive and hope you are succeful.

JD.

The lead angle is greater than the angle of slip of the material. The back driving force is overcomming the friction between main gear and worm, using single lead will generally prevent backdriving if physical dimensions will allow.

Too much grease . . .

As a thumb rule a single stage worm reducer with a ratio of less than 1:40 is usually not self locking, that is the worm can be rotated by applying sufficient torque on the wheel shaft if the lubrication is optimal.

The actual reason is because of the low reduction ratio and because you have used a 2-start worm, the lead angle has become higher than the friction angle (some call it slip angle) that is why, the worm gear box is not self-locking.

You should have used a single strart worm which would have resulted in a smaller lead angle, even then it might not have been self locking under proper lubrication.

Why did you design and build something that could be bought out of stock from over a dozen manufacturers?

Re-inventing the wheel seems to be very popular as of late!

Thanks for the reply & pointing out the mistake.

Actually it's a gear box with slip clutch at the o/p shaft (worm gear shaft) for connecting & dis-connecting it with another shaft. So I had to design it, as std gear box manufacturers were not interested.

And the reason for two start was to make the gear box compact.

AH SO!

I can see clearly now.

Good job.