Round Key Ways

[Wobbles]

The term “Dutchman” in the woodworking trade is referring to a patch that is made to hide a problem/hole/defect/knot on the wood surface.

Oh, those Dutchmen have been trying to hide and get out of work for centuries.
Haven't you ever heard of Rip Van Winkle ??

 

[quickcut]

The shaft is only 220mm long , with a flexible coupling on the one side, and a timing 8mm pitch (gates gt3 type) between two bearings. 8mm was chosen as it can go around a pulley of 32 teeth. Also their online calculators determined the belt width, which I added my own safety margin. 85mm was recommended and I chose 100mm . Secondly the amount of force to positively engage the teeth is HUGE at 6000N . This results in a shaft deflection of .013 mm in the middle between the two bearings(the load been considered as a point load between the two bearings). The bearings are roller type with custom machined housings. Plummer blocks scare me at 5000 rpm. I used two programs to determine the shaft diameter. They both gave similar results. Both have demo versions if anyone is interested. www.pwr-tools.com and http://www.mitcalc.com . Hope these attachments work??? .

 

[Heavycrimp]

I feel much better knowing the timing pulley is being run between two bearings vs. an overhung load. I did the manual calculation using the rule for a keyed shaft - Diameter (in inches) = the cube root of (40*HP/RPM). It does indeed work out to 45mm. Just bear in mind that the calculation is based on the MINIMUM shaft size that can carry the load. It does assume certain conditions and is based on some fairly conservative criteria but the designer must determine if any severity of service needs to be taken into account. I am used to working in rather severe industrial environments. I am always amazed by the ways that things end up being destroyed and believe in the maxim "Nothing is fool-proof to a sufficiently talented fool". Driving a generator presents a fairly smooth ramping of load, so shock loading in your application is minimal. A rock crusher, mechanical punch press and similar things present much more severe service and such things should be taken into account. I guess I'm saying a calculated shaft size is a starting point and then the driven equipment and environment have to be considered. I do believe in your case, the 45mm shaft should work just fine.

 

[FREDROSSE]

100 Horsepower on a 40 mm shaft gives a keyway shearing force of 4640 pounds. At this torque the shaft torsion shear stress is 4760 PSI, if it just drove a shaft with no overhung load. Additional stress from the pitchline of the pulley add to the shear stress of the torque load. With a small pulley, say 6 inches diameter, the maximum shear stress is 5400 PSI. Add to that figure if the pulley is some distance away from its support bearing, another additive stress.

Of course, with typical electric motors starting torque will be a multiplier of 2+/-, and then, if shock loads occur, an even higher stress multiplier.

Allowable shear stress in ordinary shafting is 18,000 PSI, and alloy shafts can have much higher stress. Just some numbers to get a quantified idea of this case.

 

[DKD228]

A "Dutchman" is a pin put in a drilled hole to keep the part located. The hole it drilled after the parts are mated. Sometimes the hole is threaded. The hole is drilled between both parts.

"Billy G"

Lock pin or lock screw might be a more familiar term for this trick, ...usually seen more in light duty service situations, i think ( ? )

 

[rmsflorida]

Sharp corners on the keyway are not allowed..
The US Coast Guard Std. must have a small radius on the corner of the mill cutters to release stress fractures.
Go and seek the information in the Machinist Hand book look under "Square keyways and keys"
This is what your looking for.
Regards
Robbie