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Author Topic: Bearing layout for new build  (Read 720 times)

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Amylynn

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Bearing layout for new build
« on: April 25, 2018, 09:36:43 AM »

I'm trying to plan out a build for a cabbing machine so I can start the process... but there are a few things I'm unsure of.

  I noticed most diy builds featured here have the bearings near the center of the machines. I am hoping to do something more like the pixie, and put them on the outside. I think the main reason I want to do this is because of issues I had with my (transient) Cabking... with wobbling on the shafts.

 Is this a good idea, or is there a reason most builds aren't like that?

Anything you guys know about the bearing placement will help!





I'm also wondering what kind of steel to use for the shaft, and if there's any problem with using LDPE plastic to make the housing.
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Amylynn

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Re: Bearing layout for new build
« Reply #1 on: April 25, 2018, 10:26:20 AM »

I realize also that everyone says to get a shaft with opposite threads on either end.  I am guessing if I put bearings on both sides, I can't really use the threads to make sure everything is tight...?  If that makes sense..  If I did that it would put unwanted pressure on the bearing blocks, right?  :dontknow:
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irockhound

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Re: Bearing layout for new build
« Reply #2 on: April 25, 2018, 11:26:14 AM »

Not sure of your design idea, a pic or sketch might help.  If I had a solid shaft and put the wheels center and bearings on the outside changing wheels would require dealing with the bearings.
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Amylynn

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Re: Bearing layout for new build
« Reply #3 on: April 25, 2018, 12:23:47 PM »

Basically something like this first image in this link: http://forum.rocktumblinghobby.com/thread/70002/homemade-6-wheel-cabber

Just open space in the center with all wheels. My idea was it might be better for the shaft to give it that support so I never have issues with wobbles. I don't know much about machines or technical stuff, so it might be overkill to do it for that reason. Is a 1" steel shaft strong enough to stay perfectly straight with no support?
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Slabbercabber

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Re: Bearing layout for new build
« Reply #4 on: April 25, 2018, 05:23:50 PM »

Putting the bearings outboard will make a much more stable assembly but you will need to have near perfect spacers in between.  Even a few thousandths off will be disastrous for the bearings.  Another way to do it would be to turn the shaft down at one end and install a smaller bearing held in place with a shaft spacer (they look like precision washers) a and hex nut.  The other bearing can then float.  You would still need to disassemble one end to change wheels.
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jerrysg

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Re: Bearing layout for new build
« Reply #5 on: April 29, 2018, 04:22:38 AM »

I would not use any polyethylene for the housings. Most adhesives do not stick to it. I carry a small piece of LDPE film in my tool box to use when gluing the screws to the cab because the superglue does not stick to it. Neither does J B Weld.

Best bet is probably ABS.

There was on the old forum a post that had a wonderful description and photos of a homemade 10 wheel machine. I can't find it right now but he made his trays and housing from scrap PVC sheet that he got from a sign shop. Looked great.

Jerry
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Amylynn

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Re: Bearing layout for new build
« Reply #6 on: May 08, 2018, 06:15:06 AM »

Thanks for the input!

I think I've seen that post actually. I didn't know if there was an advantage to either type of plastic. It's hard to find any technical information on some of these ideas
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Slabbercabber

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Re: Bearing layout for new build
« Reply #7 on: May 08, 2018, 08:35:15 AM »

I should have mentioned that you could use pillow block mounted bearings.  These typically can be locked to the shaft eliminating the need for accurate spacers.
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