Need Help with Bearings for Shaft

[Oso Rojo]

I'm now sure where to post this, so I'll start here.

I'm building a project that is a rotary antenna. I have a 1" OD shaft that is the mast. The mast runs vertical and will be supported by one or more pillow blocks. A stepper motor will be driving the shaft from the bottom end, connected by a flexible coupling to relieve an stress on the motor.

My question is how to support the shaft vertically. I know I need some kind of thrust bearing on the bottom, but I don't know how to do that while still driving the shaft/mast with the motor.

One thought I had is to use the adapter I'll need to get from the motor drive shaft diameter to the mast diameter. If I turn a flat face on it I could use that as one race against a thrust bearing link this;
https://sdp-si.com/eStore/Catalog/Group/486

Am I headed in the right direction or is there a better way to do this?

Thanks!

 

[GK1918]

Just trying to paint a picture, one inch dia. xx amount high. chain drive or belt drive, couple or more pillow block bearings and the need for this to sit on something and rotate..?? Oddly we just did some machining on a windmill. Some "wind engines" can exceed 300lbs plus the wheel and vane and all they
have is very simple a two round plates with the bottom one has a round trough can be done with a ball mill and steel balls as big as aggetts. Kind of just
like the link you provided. All this depends on how heavy it is. If the weight is within reason I see a slab of concrete one steel ball and the shaft center
drilled some grease good to go.

 

[Richard King]

I would think you will want to mount the complete unit in a weather-proof box with a set of seals on the top where the shaft goes. I am assuming it will be mounted outside in the elements? How heavy will be the mast be? I found this link to a sealed trust bearing like the one you have or a deep groove sealed ball bearing as they also take trust. It would help if you had a sketch. You may want to call an local industrial bearing distributor, not some large store as many of the small houses have bearing engineers working there. I was also thinking of Timken roller trust bearings with a seal on the outside like they have on wheel bearings on a car. I hope that helps a little. Rich

 

[Codered741]

Use a shaft collar, like McMaster-Carr #6436K18, or machine a shoulder on the shaft. Use this to land the shaft on the thrust bearing, supported by a bottom plate with a hole through it, and attach the stepper to the bottom. I would recommend a belt reduction, at least 2:1, no more than 4:1 without an idler, for the stepper, rather than a direct drive.

-Cody

 

[Philco]

I'm with Rich on the car front hub bearing for the mast to set on. These hub bearings are already designed for the elements. You could call around to some automotive shops & find one that they have replaced & they would probably give the old one to you. These bearings will make a roaring noise when the weight of vehicle is on it. In your application it would work just fine. Another plus to these type bearings is they already have a flange to mount it with.
Phil

 

[Ulma Doctor]

sorry for the rudimentary drawing, but it may explain the principle better than words:
i hope it helps out
mike )

 

[Codered741]

sorry for the rudimentary drawing, but it may explain the principle better than words:
i hope it helps out
mike )

View attachment 57695

It doesn't seem necessary to use a tapered roller bearing for this application. You are already supporting the shaft with the pillow blocks to eliminate the angular misalignment of the shaft, so you really just need to support the axial thrust of the shaft. A thrust ball bearing will work fine for this, and be simpler and cheaper.

Also, if you use the tapered roller, you may have to worry about the shaft actually lifting up from the radial forces of the pulley. (Not likely from the stepper, but still a potential problem.)

Something like this.

Sorry for the paint-esque sketch...


Also, it it not necessary to use the thrust bearing at the bottom of the assembly, it could be placed anywhere along the shaft and work just as effectively.

-Cody

 

[Rbeckett]

The Hub and Bearing set up would be a good solution, but they are relatively expensive. Last one I bought for a GMC truck was nearly 400 bucks. Kind of steep for a hobby project. I would use the two pillow blocks mounted to a plate and 4 locking collars. Then a gear on the lower end to be turned by the stepper. Stepper motors do well in this type of application because if they are properly geared and not stalled they will accurately position the mast pretty consistently. Depending on the electronics you use you could use the dial position to represent the actual position of the antenna on the outside. Occasionally you might have to re-adjust your actual position to match the dial inside the house, but that is done easily with the power turned off. If you need help finding the electronics or reduction components PM me and I will send you a list of suppliers I use and get very good service and prices from. Another feature of the stepper is that it is brushless so corrosion and humidity have less effect on them than a brushed motor and they also use much lower voltage to keep electrocution hazards out of the equation too. The electronics package for the motor can be housed some distance from the motor with little concern about voltage drop or resistance. Cat 5 cable would be fine for up to 100 feet. Cat 6 for longer runs would be better. Have a look at the electronics package Bill Gruby used to power his cross slide mod. It will work for you application too.

Bob

EDIT: Good pillow blocks also have an integral lock for the shaft on one side already. It is an eccentric cam that is locked in place with a collar. I would not be too concerned with using a thrust bearing unless the antenna is very heavy, say in excess of 100 or more pounds or more. Securing it against lateral forces from winds will be the most important issue from the beginning.

 

[Ulma Doctor]

It doesn't seem necessary to use a tapered roller bearing for this application. You are already supporting the shaft with the pillow blocks to eliminate the angular misalignment of the shaft, so you really just need to support the axial thrust of the shaft. A thrust ball bearing will work fine for this, and be simpler and cheaper.
A)The tapered roller bearing is not being used for misalignment, it's for thrust only and will last for years.

Also, if you use the tapered roller, you may have to worry about the shaft actually lifting up from the radial forces of the pulley. (Not likely from the stepper, but still a potential problem.)
A)the weight of the antenna and the pillow block set lock screws will prevent any torsional stresses from lifting the antenna.

 

[Richard King]

It doesn't seem necessary to use a tapered roller bearing for this application. You are already supporting the shaft with the pillow blocks to eliminate the angular misalignment of the shaft, so you really just need to support the axial thrust of the shaft. A thrust ball bearing will work fine for this, and be simpler and cheaper.
A)The tapered roller bearing is not being used for misalignment, it's for thrust only and will last for years.

Also, if you use the tapered roller, you may have to worry about the shaft actually lifting up from the radial forces of the pulley. (Not likely from the stepper, but still a potential problem.)
A)the weight of the antenna and the pillow block set lock screws will prevent any torsional stresses from lifting the antenna.

I was thinking of 2 one on each side of a plate like a wheel hub, I was just using it as an example of an assembly of a seal and bearing on both sides to keep the elements out. Be sure to order sealed bearings and not shielded. I just put a sealed deep grove bearing on a feed shaft on a 54" Bullard and it had a bearing retainer nut and star lock washer on it to keep the shaft from sliding out of the bearing I would not set the shaft on any single bearing, Just think of a high wind blowing and it gets sucked up. :ideas: