Genie SP-99 drive gear - repair

Thought I'd post this here since I'm on these forums the most. I have an old Genie SP-99 chain drive garage door opener whose chain sprocket (plastic) got chewed up when piece of rope got caught in the chain. The drive gear and sprocket were one-piece molded.

The Genie p/n is 26289R and shows up online but as "discontinued" and no longer available on EVERY website it's listed. Figuring I had nothing to lose, I "jerry-rigged" it.

I used a 1 3/8" OD x 1/2" ID flat washer and drilled eight holes around it at the outside edge so I had a 1" PD. Then I milled off the old plastic sprocket part of the gear around the bushing and enlarged the ID of the washer for a press fit on the brass bushing. I then used an angle grinder to shape the sprocket teeth. Drilled (2) holes 180 deg apart for 2-56 SHCS I had laying around (.070") thru the washer/sprocket into the plastic gear. I enlarged these holes on the sprocket to .090" for clearance of the SHCS. These are to connect the sprocket to the plastic drive gear so they turn as a unit. To be fair, I had a machinist at work drill the 8 holes, enlarge the ID of the washer and mill off the old plastic sprocket on a Bridgeport but this is something that could also be done with a drill press and a hand file.

I'll be installing it today. May need some tweaking but I think it came out okay. I'm no worse off than before in any case and if it works, it'll save me $200 for a new opener.

BTW, I DID look for a commercially available sprocket but closest thing I could find were all 9 tooth which would change the speed of the door operation.

Looks like fine work to me.

Well done!!

Update on the Genie SP-99 repair:
Was shutting the door the other day and it stopped closing but the motor kept turning. Turns out that the (2) 2-56 SHCS that I used to attach the metal sprocket to the plastic gear had sheared off between the gear and sprocket. I beefed it up by rotating the sprocket slightly to avoid the bolts stuck in the plastic gear, drilled 6 more holes and used 8 SHCS 2-56 to secure it. So, if you attempt this repair, go with 8 instead of the 2 in the original design. Hopefully, this will last me quite a while. If 8 shear off, well, then it's head scratching time. :idea:

Hello, my genie opener needs this exact part too. The rest of the machine is in good working order so I am thinking about making one of these as you did. Your part looks very good.

Can you give an update on how long the part has worked after you added the additional 6 fasteners?

I cant believe that the original part had molded nylon sprocket teeth for driving the chain, and worked for a few decades. I think the teeth must have started cracking off gradually and then more quickly when say only 3 of the original 8 teeth were left. I didnt find any traces of sprocket teeth on the garage floor except the last 2 - the previous ones must have been swept up over years.

Its not surprised that the genie replacement part had a metal sprocket molded into the larger nylon gear. That chain sprocket portion is a major stress concentration.

Thanks for any info and assistance you can provide. If you have additional photos from the time when you added the 6 additional fasteners I would be very interested. Thank you for sharing the info and pictures you have already shared.

This sounds like one of those parts that a guy could copy on a 3D printer and print made of metal and sell a few...

I have a Genie Screw drive that quit working a couple ago, don't remember what's wrong with it. Anyone want it ?
Iv'e always liked the Screw Drive, I've installed about a 1/2 dozen of them.