Hey all. I ordered a sprocket and chain system from Servo City the other day. I was going to use it for my Indefatigable class battlecruiser's dual rudder setup. However, it turns out that the sprokets I got were different pitch. The server sproket and the chain is 1/4 inch pitch, while the plain bore sprockets for the rudder shafts are .1227 inch. I thought I would just return the 1/4 in. stuff, but it turns out that Servo City is out of the .1227 inch chain for several more weeks. Does anyone else have a source for 1/4 in. plain bore sprockets that will fit on a 1/8 in. rudder shaft? I have searched the interwebs, but to no avail. Please help. OCD
another option is to buy some .250in OD .120in ID brass tube, and ream to fit .125 then a whole world of sources including surpluscenter and http://www.econobelt.com/Q460/RFQ/default.asp?Page=sprockets/4-18.htm have them
Greg, I am not sure what you mean by reaming? Are you saying, essentially, bore out the inside some .250/.120 inch tube and stick it over the 1/8" rudder shaft? I could only find .1227 sprockets on MicroMark. I didn't see any .250 pitch. :-(
basically, yes. either press it on or cut a hole and use extended setscrews, depending on accessibility requirements.
With the difference between the hole and the shaft being .005, I wonder if one couldn't heat the sprocket and slip it on the shaft and let it be a nice tight fit? I'd love to explain that one to my wife when she catches me with a sprocket in the toaster oven.
nope. cte is not large enoug to expand the bore sufficiently before melting the material. if it was .0005 it would work
I am also speaking of metal... to get a .120 inch diameter brass hole to expand to .125 takes several thousand degrees C
no way, dude. We're heating a ring-shaped object, and only need to increase the circumference (not the diameter) by like .001, if that, to expand the hole in the middle to .125". Couple hundred degrees, tops. The bearing oven on the sub doesn't nearly get to 5 or 6 hundred degrees, and the big bearing for the generators are well smaller than .005 off the shaft. And they're ball bearings, so we can't push hard to make'em fit, either.
simply do the math... CTE times temperature change has to equal dimensional change/length... (One need not work in circumference, diameter and it are off by only a factor of Pi which cancels out) brass CTE is on the order of 20e-6 /C . dL = CTE*L*dT , or 0.005 = 20e-6 * .125 * dT, giving a dT of 2000C. and for a .005 inch diametral change, the circumference has to get to a total of (.125+.005)*Pi for a change of .005*Pi on the circumference
I agree with Greg. Size matters in this case. Forget the 0.120" ID - drill it out with an 1/8" drill and use Loctite retaining compound (the green stuff) to glue it together. I've used the retaining compound to attach a slip fit pinon onto a 400 watt motor and it worked great.
If you want to use the 1/4" ID sprocket on a 1/8" shaft, an even simpler solution: Get a flanged 1/4" OD 1/8" ID sintered bronce bushing (like these:www.amazon.com/Oilite%C2%AE-Sintere...ref=sr_1_1 that are commonly used in NTXBG for stuffing tubes), to use as a shaft adapter. Drill an oversized hole through the side for the 1/4" ID sprocket setscrew, and use a longer setscrew. No precision boing needed. Cheers,
