Need help with roof opening mechanism

[angelfj]

A few years back I built my own "roll-off" roof mechanism for a backyard observatory. The roof is free to roll on an off. The mechanism is very simple. There is a long rack (linear gear) permanently attached to the base of the roof on one side. A reversible motor drives a pinion which engages the rack to move it either to the open or closed position. The roof is guided by a set of garage door rails and wheels. Recently, the pinion has been slipping out of the rack when trying to open the roof. If I pull down on the roof near where the pinion engages it does help and eventually the roof will open. However, I getting to old to do this because it takes a lot of force to keep the pinion and rack engaged. I have been trying to come up with a way to maintain the engagement between the driven pinion and rack, maybe a couple of idler pinions mounted below the driven gear and pushing it up against the pinion. The following photos should give you an idea of the setup.

Many thanks, Frank

[Toolguy]

I would make a bracket with 2 rollers (cam followers maybe) that go on top of the rack and hold it down against the pinion gear. The bracket would need to be sturdy, probably welded construction and mounted to the same panel as the motor. I would make the rollers above and 3" on either side of the pinion gear to hold it down when going either direction.

[C-Bag]

What a cool setup Frank! I love it!

While it's hard to see exactly what is up, here's my 2c. I would have used a chain drive to a jack shaft with with rack and pinion driving both sides. I'd also make the Jack shaft mount adjustable to engage the rack as things wear. I know it is a lot more expensive because of those rack and pinion, but not being able to pull the structure from the center is just asking for problems.

Short term I'd oil all the rollers as they are notorious for causing drag and also grease the rack and pinion. Personally for me the amount of motor shaft w/pinion sticking out is way more than I would have set up originally. I'd have the pinion as close to the gearbox as possible along with an adjustable motor mount that is not only slotted but has adjuster bolts that can help align the motor/pinion. Where the motor is mounted it's going to be really awkward to adjust and there is a lot of precision necessary in adjusting rack and pinion.

[Christopherbock]

Has you motor slipped down some making the angle on the pinion gear loose good contact with the rack. I likeep the idea about using cam following rollers.

[angelfj]

Thanks for the suggestions. I'm in the process of designing a motor plate and bracket to support the motor shaft which will include a bearing and rollers to maintain the alignment of the pinion gear and rack. See attached for an in-progress drawing.

Thanks , Frank

[Toolguy]

Good solid design. Should work fine for years.