Vintage Windmill and Wind Generator Forum

I looked on the forum for a Challenge 27 disassembly and rebuild and while there were posts, I had some questions still that I couldn’t find in a thread as this was my first Challenge windmill. I’m posting this to potentially help others in the future.


As with most all newly acquired windmills, I wanted to assess the bearings, wear components, clean and repair/fix accordingly, as to not regret failing to do so later.


Disassembly of a 8’ Challenge 27 was fairly straightforward, removing the guide rod bracket, crosshead, guide rods, access plugs and set screws. The bull gears removed by tapping the bull gear shaft to one side to remove one bull gear and then back to the other side to remove the other. In my case, I cut the bull gear shaft as it had some wear and I hadn’t seen the small access plug to tap the bull gear shaft the opposite way. This shaft is 1.25” diameter x about 5.75” as I replaced it.

My questions that I had at this point: 1) could the main shaft be removed with the large and small hubs attached and 2) how do I access the woodruff keys under each pinion?

Once the set screws are removed from each pinion, my front pinion slid on the shaft, so I slid it to access and tap out the front woodruff key. My back pinion was stuck good and tight to the shaft. I used heat, leverage and was able to force the back pinion partially into the rear access port plug area and then tap out that woodruff key with a punch. At this point, I still didn’t know if there was a set screw on the snoot area and if I could drive the main shaft out with both hubs still attached. I took a gamble and was able to drive out the main shaft with both hubs still attached, as there was no set screw in the snoot area. I also noted the rear pinion possessed additional notches to accommodate a thrust washer and the front pinion lacked those same notches.


I made note how the main shaft oil conveyor spring was oriented and assessed the two Timken bearings (Timken 1983 W). The two roller bearings were in decent shape, but since I had it fully apart, I wanted to not regret failing to replace them. The two bearings for the main shaft possessed notches that make contact to aide in securing them to either a pin on the main shaft snoot area or to a unique thrush washer by the rear pinion.


Upon trying to locate Timken or any similar 1983 W roller bearings, I could not locate any. Maybe the 1983 W had those factory notches already cut or maybe they were added at the Challenge factory, I did not know. I found that # 1985 were identical, but lacked those thrust notches, so I cut my own thrust notches with a Dremel tool. There might had been an easier way to cut them, but it took about 20 minutes per bearing to cut them after measuring several times.

My next question I pondered was, how hard was it going to be to reset the snoot plate (the parts list calls it a “nose piece”) with the hubs still attached to the main shaft? Dan Benjamin gave me some good advice and it was determined that the hubs should be removed from the main shaft to properly and fully secure the snoot plate during reassembly. He also relayed that some gasket maker around that snoot plate, once installed, could be helpful. The snoot plate keeps oil from leaking out of the snoot/shaft.


Removing the large and small hubs from the main shaft was not too bad. I had previously removed the set screws from each hub. When I had driven out the main shaft out of the gearbox, the large hub moved some, exposing the gibs key more. Using some heat, a hammer and a punch, I was able to remove the gibs key from the large hub. The smaller front hub was more stubborn. The small hub key IS tapered, so my intent was to drive the key out the front of the small hub. Heat, pressure and a punch didn’t convince that key to move, so I relieved some pressure on that key by drilling through it length wise along the shaft, trying not to damage the shaft. Using some additional heat, a hammer and a punch, it came out.

The crosshead pins (all three) were frozen and the 5/8” pump rod thread was broken off in the crosshead. Not sure how the pump rod broken off like that, but I removed the broken off pump rod thread and made new pins for the crosshead.


The tail pin housing in the gearbox has a place for a removable bronze or similar style bushing, which I thought was impressive in design. I recall that bushing was .75” bore, 1” OD and 1 1/8” long.

The flat bar for the vane spring is 8.75” in length. Mine was missing, so Dan B relayed that measurement.

I replaced the mast pipe as well.

To me, the Challenge 27 is similar in design to that of a Dempster, but much easier to work and much better designed. This Challenge 27 had sat for no telling how long without a bonnet and still rotated fine. I have an additional 8’ Challenge 27 gearbox with the bronze bushing/bearing that I might rebuild at some point. I wonder which design is better, the roller bearing or bronze style.

The green paint is what I had on hand.

Michael , almost appears to be the same sequence on the input shaft as a Dempster #12 , 10 ft'r

Thanks 150% for the tutorial. Many can use it as a reference, including me when I get to my 27 overhaul. I have written extensively about Dempsters, and consider it helpful when other choose to look it up and utilize the information.

The effort you put into the overhaul, and pictures and explanations are valuable beyond compare. Thanks again.

Thank you.

Here are a few more photos.

New mast pipe as the old mast pipe had some wear. I just need to cut it down to the appropriate length.


I made this pullout tube and the chain is intentionally too long, which I’ll ultimately cut down. A Dempster pullout swivel would work as well.


Bull gear shaft and retainer/spacer. The set screw keeps the bull gear shaft from spinning. It think I drilled it about 1/4” deep.


New brake rod. Took a piece of round stock and drilled the holes for the cotter pins and then welded two washers to the end that the tailbone will make contact with.

Thank you for the details Michael. Will be very helpful on our 27.

Michael these parts came with my NOS 27 i haven't taken the time to figure it out yet but maybe this will help you

Thank you.

The parts I marked in red are the parts that I don’t directly recognize as they relate to a Challenge 27, but I don’t have many much experience with a 27 either.

I have done the Dempster pullout switcheroo on many mills. Hard to beat a system like that.

Dan,

If you have a pump rod for that 8’ 27 NOS, I’d be interested in the length of it. If not, I’ll just make one on the longer side. Thanks