The Grafton Joystix are CNC machined from 7075-T6 aluminum alloy. Each of the arms is machined from a single piece of billet aluminum, so the right arm and its spider are one piece. At the pedal spindle the arm is 1" (25.34mm) wide, it narrows slightly above it to 19.3mm, then gradually widens to 36.81mm at the B/B spindle hole. Both arms share these dimensions. At the pedal, the arm is 15mm thick, adding thickness gradually up the arm to the B/B spindle. On the left arm it's 25.81mm thick at the B/B, the right arm, at 26.08mm has slightly more material to support the arm on the spindle. A cut is made by the milling machine at approximately 45 degrees around the entire upper perimeter,cutting the corner away giving it an angled edge. This same angled cut my the milling machine is made on the reverse around the length of the arm, omitting the B/B spindle area.
The spider has a swept arm to the right design. Each spider arm has a 6.7mm thickness, but is 13.81mm thick to make the drilled and tapped post for the inner fixing to thread into. The end of each arm is machined to a 3.6mm thickness to properly hold the middle and outer chainring.
Around the B/B spindle, on the back side, the aluminum is milled away reducing the 6.7mm thickness in these areas to 3.50mm You will notice that many of these dimensions, measurements, and style of construction are rather similar to those used on the Sims cranks, this is because Benson Sim was once Mr. Grafton's sub-contractor making the Grafton arms (Grafton has no machine shop of his own), and began making and selling cranks under their own name when Mr. Grafton was unable to meet his commitments, (also, see the Topline story).
The pedal spindle hole is drilled and tapped with 9/16" by 20 TPI threads. The crank arm dust cap holes are bored and tapped with 22mm by 1mm threads. The square tapered hole for the B/B spindle is milled to shape as a part of cutting the rear of the arm. Each of the arms is polished, then anodized, if it to be colored, or left un-anodized yet high polished if it is to be Silver.
Joystix crank arms come anodized in Blue, Black, Lavender, Red, or Silver. They are made in 170mm, 172.5mm, 175mm, 177.5mm, or 181mm lengths. Grafton Joystix cranks come as right arm, with integrated spider, left arm, a set of five steel outer bolts and nuts, and a set of five steel inner fixing bolts. Chainrings, crank arm bolts, and crank arm dust caps will be needed separately. We found Joystix Mountain cranks had a Bike-Pro Q measurement of 154mm. The weight of the 175mm long Joystix Mountain crank arms is 439.5 grams, the nut and bolts sets weigh an added 38.5 grams. Made in USA. Specify length and color.
Size-70-72-75-77-80 Color-B-BK-L-R-S $ Price in Catalog
Grafton Hyper-C Mountain Crank Arms
