Hovercrafter

The Elusive KOP-FLEX Coupler

Seems of late there has been much discussion/questions about the coupler used for our higher horsepower Hover engines.

I will outline here what I know of the KOP-FLEX coupler and my installation to the Subaru EJ-22 engine. The coupler I obtained is designated as the 1 1/2 W sleeve and hub. W stands for Waldron. UH has been using the "H" series coupler. The two are virtually the same, the differance being the gear and or tooth design. The "H" having finer teeth and the "W" coarser. I purchased mine from Ebay and saved big dollars!! The hub is the expensive component. You size this to the shaft you are going to fit the coupler to. I have a 1 3/8 inch shaft, so my hub is a 1 1/2W HUBX 1 3/8.

You need to have the fly wheel machined some ot accept the coupler. The coupler is 6 inches in diameter. The flywheel stock had a recess around the crank bolts of aprox 5 3/4 inches, so this needs to be turned out a bit on a lath and then drilled and tapped for the (8) 3/8 inch mounting bolts.

Next, you need a cap made to fit over the flywheel crank bolts and provide a sealed gasket surface to mount the coupler to. Essentially you end up with a spacer/cap that shims the coupler out to the clutch plate surface of the flywheel. The coupler mounting bolts, in my case 3/8 x 1 1/2 inch socket head cap screws, go through the spacer and thread into the flywheel.

Here are all the components...flywheel, spacer/cap, sleeve, hub, shaft, gasket ,o-ring and retainer, coupler grease, keystock, and bolts.

I had the work done at a local machine shop. The estimate I got came to the same cost as it would be sending the flywheel down to UH and getting the spacer from them as well, but I would save dollars on shipping. That plan turned into a disaster, while the work is good, the cost went WAY over the estimate. In hind site I would have been ahead to pay the shipping for getting the flywheel to UH and have the work done by them and pay a known cost. UH always has a fast turnaround, great customer service, and will do good work. Pinching pennys here burned me good this time

OK, so moving along, I now needed to fit the hub to the shaft. They bore these with a interferance fit. The instructions say to heat the hub to 350 degrees and install to shaft. The hub can go on the shaft with either a long or short portion fprward out of the sleeve. I went with the short nose out which turned out to be the right choice as the mounting configuration does not alow for the longer. well it would, you would just push the hub back in the sleeve. After the hub was in the oven for about 45 minutes I was pleases to have it slip on the shaft with no trouble at all, then let things cool down.

I mounted the flywheel to the crankshaft. The odd bolt you see is a replacement is\\ for the one I brought to the machine shop for reference, which they lost.

Then the Spacer/cap fits nicely over the crank bolts. I am also showing the coupler gasket.

Next apply grease to the hub and sleeve gear and teeth, slide the shaft and hub through the sleeve and o-ring seal and engage the gear. Then place the gasket in between the spacer and sleeve and bolt it through to the flywheel. Of course to do this you have to have the pillow blocks and  pulleys on the shaft as you put the coupler in place. Then shim the pillow blocks, truing the shaft.

After all is tightened down, there are two grease holes capped with grub screws used to fill the coupler with more grease.

Here is a picture showing the clearence between the coupler and the forward bearing. There is about 1/2 inch between.

So there you have it. Not a cheap or easy retrofit, but pretty straight forward once you get all the pieces. I hope this helps for those soon to make the same journey. I look forward to seeing what I missed and what else works as other projects out there share their experiences.

Next for me will be starting it up...I hope anyway..................

Greg