Bearings on carriage: why 2-1 bearing arrangement?

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shocksofmighty
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Bearings on carriage: why 2-1 bearing arrangement?

Post by shocksofmighty » May 8th, 2017, 2:25 pm

Is there any particular reason why some (all?) of the i3 models have two linear bearings on one side of the Y-carriage and only one on the other? Using a glass plate, I am seeing slop in the bearing due at least in part to the central pivot of the single bearing on the right side of the carriage. This also makes leveling quite a pain. I can easily drill some new holes and add another bearing, but I was curious if there is some reason (beside from being cheap) that this wasn't done in the first place.

shocksofmighty
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Re: Bearings on carriage: why 2-1 bearing arrangement?

Post by shocksofmighty » May 21st, 2017, 8:56 pm

I went ahead and added a second pillow block bearing on the right side. Drastic improvement in the amount of play in the carriage. I can now use somewhat beefier bed springs with essentially no re-leveling.

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Chaco
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Re: Bearings on carriage: why 2-1 bearing arrangement?

Post by Chaco » May 31st, 2017, 2:50 pm

from what i have read online, its a design standard using a triangle arrangement to have the x carriage not wiggle.
this helps keep the carriage straight and not wobble and also not have any of the bearings act as a brake to the others

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Meduza
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Re: Bearings on carriage: why 2-1 bearing arrangement?

Post by Meduza » June 1st, 2017, 2:33 am

three points define a plane, four make it overconstratined and prone to wobbling and drawer slide effect.

shocksofmighty
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Re: Bearings on carriage: why 2-1 bearing arrangement?

Post by shocksofmighty » June 1st, 2017, 6:47 am

How is four points overconstrained AND prone to wobbling? That doesn't make sense to me. Assuming that drawer slide effect references one side binding the other side during movement, that seems possible, but not likely if it is setup correctly. The bearings do provide some tolerance as well.

Again, I see haven't seen an ill-effects from moving to four bearings, though the problem I am correcting is really the flexibility of carriage itself. There was a lot of vertical movement on the right side, as the single bearing provided a pivot point. Two bearings eliminates that.

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Roberts_Clif
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Re: Bearings on carriage: why 2-1 bearing arrangement?

Post by Roberts_Clif » June 7th, 2017, 10:04 am

I have been using 4 bearing for about 8 months never had a problem.
Only problem ever had was when there were only 3 bearings as the carriage would move funny on the Right hand side causing uneven print lines.
Most likely because they were inferior bearings.

Was using four printed Bearings during this time. About a week ago they started causing problems and were replaced with Original style non inferior bearings, still using 4 bearings.
Attachments
Four Bearings.jpg

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