Fan Shaft Braking Device

[coss]

This design involves adding Differential Holdback Band Brakes on 4" Steel SAE 1040 Shafts in which three high-strength A490 bolts will be used to attach a 3/4" thick, 8" Diameter steel plate to the non-drive side of the shafts instead of a coupling because only about 1/4" of shaft emerges from the bearing. An 8" Shaft extension with keyway will be welded to an identical steel plate in the Machine Shop, and will then be bolted to the other plate at the site. Band Brake gets mounted on Plate and keyed to the Shaft Extension. All bolts will be "Loctite in place". The question is will tapping and threading 1 1/4" long and 1/2" Diameter holes into a 4" Steel Shaft causes cracks to form and propagate into the shaft over time at the location of the bearing or will the shaft experience an unacceptable rise in stress from the drill and tap?
Thanks!
Coss

 

[automatic2]

(3) 1/2" bolts in the end of a 4" shaft to hold a 3/4" x 8" coupling plate/ shaft extension used for braking?. You've said nothing about the shaft speed. I'd run like hell if I ever came across such a device. Watch your liabilities.

 

[coss]

automatic 2
Typical shaft speed is 286 RPM at 167 Hp. The plates weigh about 30 lbs. total, and then an 8" Shaft Extension which sits inside the bore of the Braking Device. Prototype has already been built and tested yet my question is still about the effect of drilling (Metallurgy) at the three 1/2" drilled holes. For more info see "Steel Shaft Design Safety Factors" posted March 14, 2003 in this same Forum.

 

[olympic]

There is something lost in interpretation. Can you attach a drawing please??? The problem otherwise doesn't sound too complex.

 

[nickelkid]

The effect of stress risers created by 3 drill point points in end of the shaft is probably impossible to calculate. Numbers might be published, but I would look for alternative fastening methods like an interference fit between the plate and the shaft. You may need a hub, Machinery's Handbook can help you out for sizing.