Constructing Janus, by Dirk

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Re: Constructing Janus, by Dirk

Postby dirktheeng » Mon May 09, 2011 10:42 pm

bdring wrote:Be aware that all R4ZZ 1/4" bearings are not exactly 0.250" I.D.. They are actually 0.2465 I.D. When you see fractions used for bearings you need to check the actual size. That holds true for a lot of things like pipe, conduit etc. Blame our English measurement system. Precision 0.250 shafting will not fit.


Good to know! I would have checked b/4 ordering but I left my calipers at work
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Re: Constructing Janus, by Dirk

Postby dirktheeng » Mon May 09, 2011 10:48 pm

bdring wrote:Be aware that all R4ZZ 1/4" bearings are not exactly 0.250" I.D.. They are actually 0.2465 I.D. When you see fractions used for bearings you need to check the actual size. That holds true for a lot of things like pipe, conduit etc. Blame our English measurement system. Precision 0.250 shafting will not fit.


That's actually interesting because VXB's site says:

•R4ZZ Size: 0.2500" x 0.6250" x 0.1960"

I will get my calipers wednesday and double check
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Re: Constructing Janus, by Dirk

Postby bdring » Mon May 09, 2011 11:52 pm

Read the comments section on VBX. I wanted to use a decent shaft for the Y drive shafts rather than threaded rod, but found they would not fit through the bearings.
Bart
"If you didn't build it, you will never own it."
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Re: Constructing Janus, by Dirk

Postby dirktheeng » Thu May 12, 2011 10:10 pm

bdring wrote:The nuts can be frustrating. Tim did a great job of listing the nuts in the build instructions, but you will miss some. Regardless, you will probably want to add your own mods later and the post assembly nuts will be needed.

We almost need the instructions to go step by step on each piece where it says put 5 nuts in front of you. Install piece x. If you still have nuts in front of you, you screwed up. Stop, and go back a step. :)

Dirk, if you want access to edit the build instructions, please let me know.

I have said before.... While the post nuts are more expensive, you will be more than happy to drop $5 bills into the slots rather than take apart at some point.


Bart,

It may be worth giving this task to a volunteer who will be doing a build from scratch to do it along with them as they build it. I won't remember when and where and how after having built it now, if I had thought of it I would gladly have done it.
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Cable Carrier question

Postby dirktheeng » Fri May 13, 2011 1:07 pm

All,

about ready to order a couple parts and was looking into the cable carriers. It looks like the BOM only lists 1 carrier that is 34 links long. Is that supposed to be for both axes or just one. If just one, which one and how long for the others? How many links are supposed to be in each axis (not counting the end pieces).

Thanks.
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Re: Constructing Janus, by Dirk

Postby cpdude » Fri May 13, 2011 1:19 pm

@Dirk - The BOM specifies the the cable carrier for the Y axis. Take a look at (viewtopic.php?f=28&t=423) for details on the optional Y axis cable carrier. You know this site has a search feature. :-)

Brian
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Re: Cable Carrier question

Postby twehr » Fri May 13, 2011 1:23 pm

[quote="dirktheeng"]All,

about ready to order a couple parts and was looking into the cable carriers. It looks like the BOM only lists 1 carrier that is 34 links long. Is that supposed to be for both axes or just one. If just one, which one and how long for the others? How many links are supposed to be in each axis (not counting the end pieces).

Thanks.[/quote]

Read this - full explanation: viewtopic.php?f=28&t=423&p=2559
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Re: Constructing Janus, by Dirk

Postby cpdude » Fri May 13, 2011 1:25 pm

Ooops! I meant to say "optional X axis cable carrier".

Brian
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Re: Constructing Janus, by Dirk

Postby dirktheeng » Fri May 13, 2011 3:13 pm

Thanks... I did a search but I missed that post.
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Upgrading the motion shafts Cntd

Postby dirktheeng » Fri May 13, 2011 9:27 pm

All,

I contacted a manufacturer and they gave me the following specs for the RZ44 bearing type:

0.2500 +0 -0.00031

Bart confirmed this finding when he tested the bearings witha calibrated shaft and found that 0.249 would fit and 0.250 would not.

The shafts from McMaster are

0.2500 +0 -0.0002

This means that there may be a clearance issue but if there is then it is going to be VERY close. It is close enough to easily press fit the shafts into the bearings. Even 0.001" diameter difference isn't hard to deal with. If worse comes to worse, I can chuck it in my drill and take some 3000 grit paper to it and take off a few ten thousandths to make it fit well.

From my earlier post, I am going to drop using colars and just glue the shafts into one of the bearings if I don't have to press fit them in. The shaft works out to be about 50 cents an inch, so we can upgrade from the bolts supplied in the kit without much added cost.

The real cost comes from the shaft couplers on the Y axis motor. I called missumi about the shaft couplers I wanted to use, and they said that they would probably have backlash in them. He suggested:

MCGS16-5-6.35 at $15.40 a piece - a single disk type coupler.

If I don't need to put any shaft colars in and I can make the shafts rigidly mounted in the bearings by either press fit or super glue, then I don't need the spacers either and my cost comes to:

$30.80 for the couplings and $19.68 for all the shafts, for a total of $50.48.

it would take aobut $0.75 to upgrade each idler from the kit. The rest of the expense is in the drive shafts for the Y axis.
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