Power Coupler Square Dowel for Shopsmith NEW Design

Description

This coupler is for a standard shopsmith that has a drive hub with 4 grooves and  the accessory hub has 5 grooves. There is an alternative design which uses a spline. Please make sure you select the correct version or request a special combination at the time of your order.
This power coupler set allows a custom coupling length, as short as 2.6 inches to as long as 38 inches, the standard coupler is 5 inches long. These parts are 3D printed, using a ABS filament material. 3/4 inch square wood dowel may be cut to desired length. Use of a softer wood is advised, as the wood is cheaper than the adapter to replace if an overloading event happens. The coupler ends may optionally be retained with the provided washers and screws.
Torque testing with a knot free poplar wood dowel purchased at Lowes showed to have in excess of 23 ft-lbs strength before the wood dowel broke.
I developed a new design because some of my customers were able to break the original coupler during their ordinary use.  I have worked with these customers to change the design to make it more robust. The change which seems to have helped most was changing the material to ABS from PLA.  ABS is tougher and more consistent during printing (although more difficult due to high air and print platform temperatures).  I also thickened the tube wall.  I have eliminated the cross drilled retainer holes.  Hub engagement is shortened to allow more headstock/accessory mis-alignment. Now the typical torque test failure is rounding off the wood dowel.
The belt sander accessory is the hardest on my 3D printed couplers.  I bought a belt sander accessory last year to figure out why.  There are a number of potential issues. First is centering alignment between the headstock and beltsander,  it needs to be very good, preferably less than 1/16 of an inch, also the length of the dowel needs to be on the longer end, probably 1.5X the OEM coupler length. If not aligned there will be plastic debris from internal grinding. Another possible issue is shaft runout (slightly bend of shaft) on the beltsander, as an accessory sometimes things get accidently bent, which would exhibit itself as grinding too. Aligning the shafts isn't difficult but will take several minutes to an hour depending on how rusty things are.  Both vertical and horizontal centering can be adjusted.
Another Belt sander concern is belt tension, especially if the rubber roller has age hardened.  People tend to tension it greater, which dramatically increases the torque load, this might be evident by the headstock struggling on start up.
While my 3D couplers have good static torque strength, they will not hold up with cyclic fatigue stress from mis-alignment, and high drag from excessive belt tension, particularly if one or more of the couplers has snug fit on one of the stub ends and a snug fit at the wood dowel interface. If the coupler gets "wear in" at lighter loads on an accessory like a bandsaw, to loosen up the fits, they can hold up better, but still it is only a matter of time before grinding takes off the nubs inside of the coupler unless shaft centering is adjusted.
If you have doubts about compatibility with your belt sander, the OEM Shopsmith coupler may be a better option.  Shopsmith claims their coupler is indestructable.  My 3D printed one isn't. That being said, if the alignment is good and belt tension isn't excessive, the coupler will last, I haven't broken one yet, however I am not using the belt sander day in/out.
The following YouTube video shows the adaptable coupler running over the range of speeds and shows that a shorter wood dowel should be used when running at the high RPM's of a joiner or planer.
https://www.youtube.com/watch?v=hEg36ctsjWc
(if the link doesn't work search for: power couplers in use )
The following YouTube video shows comparative strength testing of power couplers (Hopefully I will be updating soon with the next generation couplers):
https://www.youtube.com/watch?v=F22xO0QOZbM
(if the link doesn't work search for: Shopsmith Power Coupler Testing: Part1 Summary Results )
https://www.youtube.com/watch?v=UL4M1D6Ie1c
(if the link doesn't work search for: Shopsmith Power Coupler Torque Testing: Part 2 All Tests )
https://www.youtube.com/watch?v=
CscRqpZKiFQ
(if the link doesn't work search for: Shopsmith power coupler testing part3 retest and redemption)
If you purchase the wrong adapter for your shopsmith and need to exchange for the correct one, the incorrect one will need to be sent back for a refund and the correct style purchased under a separate transaction.  When the incorrect item is received a refund will be issued minus a fee of which covers my cost for the initial shipping.
Rather than buying dowel, the user could also rip his own 3/4 inch square wood dowel stock as well. Wood dowel at Lowe's or Home Depot < for a 36 inch long dowel. Use of a soft knot free pine is recommended rather than a higher strength wood like oak or hickory.
Do not use a coupler that shows any signs of delamination, cracks or visible defects. Do not attempt to repair the adapters.
I am liable only to the extent of the purchase price of this part. Use at your own risk. There is inherent risk using any Shopsmith equipment, loads, imbalance, speeds, feeds, and setups are determined by the user. If you do not agree to the limits of my liability please do not purchase this item. If you are not happy with this item for any reason within 30 days of purchasing contact me for details on getting a refund.
This power coupler is not related to the shopsmith company or any authorized retailer of shopsmith equipment in any way and would not be endorsed for use with shopsmith equipment.