TheSkySearchers

This is what I found before my wheel change a few months ago:

Depending on the position of my ExploraDome, it took between 10 and 25 pounds of tangential force to start it moving, and between 8 and 20 pounds of force to keep the dome moving. It varies depending on the position. I jacked up the dome a bit, cleaned the wheels and track, and rubbed a litte bit of silicone lube onto the track. This helped somewhat with rotation, but was only temporary. I decided to get new vertical wheels, a bit larger and narrower than the originals, which were about 13 years old. The horizontal wheels seemed fine, only needing cleaned and lubed.

Now, after wheel change, bearing clean and lube, and lowering some of the horizontal wheels that were slightly binding, it takes about 9 pounds of force to set the dome moving, regardless of position, and between 7 and 8 pounds of tangential force to keep it moving. I am planning to install better wheel bearings on some nice day this spring. Hoping to get the required tangential force down to about 6 pounds or better. Small gains will help.

The goal is to be able to reach up from a low sitting position, and rotate the dome a bit, without getting up from the eyepiece position. With the new wheels, I can do that now, but the easier, the better. Hopefully, better bearings will help a little. ??

Nice job!

When I measured mine (with metal rings) prior to ordering a rotation motor, I measured 10 lbs acceleration force and 5 lbs steady-state force. I calculated the torque for the motor based on that and ordered accordingly. I have noticed that, lately, even when starting up with a 1-second acceleration phase, the motor is skipping a couple of steps. I probably need to lube the wheels. They are ten years old and have never been lubed since I installed them.

What did you use for a lubricant?

KathyNS wrote: ↑Fri Feb 24, 2023 8:32 pm <snip>

What did you use for a lubricant?

I used Dupont Teflon Multi Use Lubricant in a spray can with a thin straw. The claim is, that it dries to a waxy coating, that doesn't pick up dirt and dust as much as common lubricants. If the bearings are really dirty, they can be first cleaned in a degreasing type of solvent.

The brackets that ExploraDome uses make it hard to use common skate bearings, with the 8mm hole. I had to either reuse the bearings, or put new ones in with a 6mm hole. The new ones are labelled 636 ZZ. They are also called 6 x 22 x 7 mm bearings. I replaced some, and re-used some. With the new ones, I used SS washers as spacers. Some new bearings come packed in thick grease to prevent pre sale corrosion. They should be lubricated with something thinner prior to use, to have less rolling resistance. They are actually skate bearings, ABEC-1 rated.

Thanks! That is very helpful information.

Kathy,
I just finished cleaning my plastic wheel tracks, and realigning the wheels. Wheels were new last summer. The bearings all spin quietly and easily. I was only able to reduce the tangential force needed to turn the dome by about one pound. I guess that's the best I can do with plastic tracks.

PS: I have found there are all kinds of bearing specs, and they are not consistent. Trial and error, mostly, with ordering bearings, unless you have a well stocked skate shop nearby where you can actually see the bearings. The ExploraDome brackets are sized to fit 6 mm by 31 mm axles. Standard skate spacers are about 23mm long. I don't know where they got those odd bearings. The only way to match everything for new bearings is to use some sst 6 mm flat washers.

Kathy,
With the aluminum wheel tracks on yours, I would think that it would roll much easier than mine does. I may eventually try some larger wheels and better bearings.

John Fitzgerald wrote: ↑Thu Mar 02, 2023 11:30 pm Kathy,
With the aluminum wheel tracks on yours, I would think that it would roll much easier than mine does. I may eventually try some larger wheels and better bearings.

I hear that the plastic gives much higher resistance on turning. I have no experience with the plastic rings.

I have been quite happy with my dome's rotation, until this week. We had one clear night, but I had rotation problems. I noticed the downloaded images were getting darker from the left. The guider still had good images. I couldn't think of what might be causing it, so I turned on the lights and checked on the security cameras. The dome was out of position, and the scope was obviously tracking away from the slot.

I was able to get it parked and closed, but I haven't had a chance to debug it yet. The most likely thing is something weather-related: either too cold, or some ice in the bearings or rubbing on the dome. The stepper that does the rotation has enough torque when things are working well, but only just. The nice thing about a stepper motor is that if it can't rotate, it just makes loud noises. Nothing bad happens. Unlike my shutter motor, which will snap the 90 lb-test cable if the shutter stalls!

Kathy,
Security cameras? How far is the dome from the residence? Mine is only about 50 feet from the back door.

I have worked on, and tweaked my dome rotation some more. With some new wheels, spacers, and bearings, and trial and error, it now rotates so easily, that 5 pounds of force will start it, and two to three pounds will carry it around. The wind might even rotate it a bit now. It is so free, with a moderate one handed push, not a hard push by any means, it continues for over a half turn.