PropExtension

PropExtension

We are novice machinists and so the shrink fit Milholland prop extension was a technical stretch... First, we made sure the crank extension contact surface was smooth - installed the woodruff key with a vice to be sure it was fully seated and parallel with the shaft... We then took the unheated extension and held it up to the crank end to see (eyeball) if the woodruff keyway had clearance over the installed key and the fit of the extension seemed loose enough that heating would let it pass onto the crank... Our extension was loose to tight around it's circumference as it rocked on the end of the shaft...

Next we measured the prop extension to determine how long the bolt shank had to be to press the extension against the oil slinger ring on the crank - (the extension is driven hard against the oil slinger ring) - ... We measured several times and worked out the requirement to cut 1/2" off the provided bolt... Part of the measurement process was running the bolt down in the crank to figure out how deep the threads were being sure not to force the bolt - the threads appear to go further than the bolt will go without damage...

We made a jig to hold the oil seal (with oil in it) so we could simply stick the extension thru the seal on the way from the oven to the crank... We used a piece of 3/4 plywood, a 2" hole saw thru the first 2 plys and then a 1.5" hole saw on thru the board... This jig worked perfectly...

The crank was mounted vertically in a vice ( you can bend the crank with this mounting so a rest against the first throw below the hub would be best) seated against the cut end washer and held by gripping the cut end bolt head... We mounted this way because we thought some hammer blows would be required and that proved to be true... The oil seal jig was clamped next to the vice - the seal was put in it and filled with oil... A small keg (emptied for the occasion) was put beneath to sit the heated prop extension assembly on... We laid out a heavy hammer and a steel plate to drive against the end of the prop extension...

Our stove was a couple hundred feet from the vice so we borrowed a cast iron cooking pot to hold the heat when we transferred from stove to workbench...

Our oven thermometer showed the oven thermostat off 25 degrees so we calibrated the oven for 375 degrees and removed the broiling tray to use as a carrying tray plus put a heavy set of leather gloves with it... We put the pot, lid and extension in the oven and heated as (separate) pieces for 2 hours at 375 degrees...

With the gloves on we put the extension in the pot covered with the lid and put the pot on the broiling tray... The tray transported to the workbench in less than a minute... We pulled the lid from the pot... Picked up the extension eyeballing the woodruff keyway, stuck the extension thru the oil seal in the jig, lifted and moved up to the end of the crank and started the extension on the crank located on the woodruff key...The steel driving plate was put on the end of the extension and it took about 10 hammer blows to get the extension down against the oil slinger so that the oil slinger would not move... We let the assembly cool over night, wiped the excess oil from the oil seal and installed the prop extension bolt the next day with Loctite and a torque wrench... Pictures of the main events follow: