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Crank/Bearing Clip Discussion
04-19-2014, 03:49 AM (This post was last modified: 04-19-2014 03:59 AM by jmccartney.)
Post: #1
Crank/Bearing Clip Discussion
The crank/bearings currently attach using a "clip" method. It has been noted that there could be a weakness in this particular area of the design. Lets discuss options. I do feel a little apprehensive talking design changes without a actual working Shellmo to judge, but as I am modifying parts to print on the replicator 2 around .2mm resolution it would be nice to work in any easy fixes now.

I am attaching a picture of a bearing cover that I designed today. Rainer suggested this concept. He also suggest enclosing the entire top, right now I am going to leave it open because I like to look at the insides. At some point closing it makes a lot of sense to me.

This last picture is from Sho (originally posted on the fb group page) showing prototype v3 of Shellmo with a "under support."


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04-19-2014, 08:44 AM
Post: #2
RE: Crank/Bearing Clip Discussion
Hello James,

I would place the bearing slit out of the middle. This bearing has to withstand two forces:

Upwards force by the legs to carry Shellmo's weight and
forward forces generated by the worm gear.

A slit in the middle could be opened by the gear forces. Or at least you will have some extra wear at the slit.

[Image: 2014-04-19.003029-k.jpg]


You could build an U-shaped bearing without any disadvantage
[Image: 2014-04-19.003035-k.jpg]


I agree with you to have an open cover for trials. Give it some cross beams and ears for M3 screws also in the middle section.
[Image: 2014-04-19.003041-k.jpg]


Rainer
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04-20-2014, 11:02 AM
Post: #3
RE: Crank/Bearing Clip Discussion
(04-19-2014 08:44 AM)steamboat Wrote:  Hello James,

I would place the bearing slit out of the middle. This bearing has to withstand two forces:

Upwards force by the legs to carry Shellmo's weight and
forward forces generated by the worm gear.

A slit in the middle could be opened by the gear forces. Or at least you will have some extra wear at the slit.

Yeah, I think this is where I don't have the skills required to do the mechanical design portion of these modifications. Your explanations make perfect sense now that you mention them.

I will have to think on it, right now the most noticeable problem is needing the cross members and its evident now that I have printed the test cover, that it needs tied down like you mentioned in the middle with screws, but placement is going to be an issue.
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