Easily adjustable belt tensioners for Rostock Max V2???

[esbowman]

UPDATE: Here is the latest STL file if anyone is interested in printing these. Please leave feedback if you have any suggestions to make it better. There are also a couple of other ideas from members in this thread that hold promise IMO. They are worth checking out. Thanks!

Better explanation on how to install the tensioners can be found here. http://forum.seemecnc.com/viewtopic.php ... =40#p40074" onclick="window.open(this.href);return false;

rostock max v2 belt tensioner v27.stl

Rostock Max 2 Belt Tensioner - by esbowman - V27

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I apologize if someone has already asked this question, but do you guys know of a belt tensioning upgrade for the V2? Not that it's incredibly difficult to adjust them now, but something like the version Barnett posted here (https://www.thingiverse.com/thing:87463" onclick="window.open(this.href);return false;) would be awesome. That one is for the Rostock Max V1 from what I gather, and would not work on our V2 printers due to the lack of a bolt hole above the bearing assembly.

I'm thinking about taking on the task and posting something for everyone. I have a few ideas in mind. Anyone? Has this been developed already?

[esbowman]

I spent some time today and ran out a prototype/idea that might have some promise. Before I try to install one of these, I'd like to get some opinions from all of you regarding this.

The difficulty is coming up with a design simple enough to work with the single hole we have in the melamine panel. The first Rostock had two holes and in my opinion makes a custom tensioner even easier to develop. What I've come up with MIGHT work, but I feel it needs some tweaking. The general idea I have is to make a tensioner that installs on the single screw, with a socket head cap screw added for adustment. The possible downside is that this would put pressure on the melamine panel, but I don't think it would be enough to break or stress the melamine panel. Not sure though. The other issue with this design is that it doesn't allow for a ton of adjustment due to space limitations. That said though, I think it could still work, or at least seems like it would on my printer and the way I have the belts tightened at the moment. I'm happy to develop something for all of the v2 users out there, if I can get some feedback on this design. I'm sure we can all come up with something that would work.

Final thought...Am I overthinking this? Is there even a desire to have a more easily adjustable tensioner? Your advice and feedback are greatly appreciated. Thanks!

Left side view

Right side view

Bottom view of belt tensioners - buttons would be placed on the bottom of the adjustment screws to keep from marring the melamine panel and hopefully keep the bracket upright.

Set in place for visualization - not installed yet

[Eaglezsoar]

There most certainly is a need for a tensioner on the V2 and yours is the first one that looks like it may actually work. Even the tensioners on the V1 did
not have a lot of room for adjustment but offered just enough to allow you to level the upper pulley so the belt may run in the center of the pulley. Your idea for the V2 seems to offer close to the same range of adjust-ability and I would definitely take this to fruition to benefit all V2 owners. Great job in coming up with something that looks like it will actually work.

[atoff]

Looks good... I'm definitely interested in a tensioner for the V2! I was originally thinking of creating a "cap" that would fit the post; Something that would end up looking like this: [img]http://i.imgur.com/3FnY9pu.jpg[/img]

...minus the middle spacer... but that would create about a 2-3mm gap at the top plate.

I don't think your design would create enough pressure to cause damage... seems ideal. A bigger / wider screw cap would help.

[Eaglezsoar]

I agree that a larger cap at the bottom would help distribute the stresses involved but you can't go too much larger.
I like esbowman's design just the way it is with Atoff's idea of the larger cap. The design seems perfect for the V2.

[esbowman]

I thought about doing some sort of a cap but that would likely cause the top to sit up higher and the acrylic panels would not fit as well. I'm sort of OC in that regard.

I'm working on the next version now actually. I'm thinking about having two adjustment screws instead of one. I think this could spread the load a bit more and prohibit the tensioner from accidentally rotating. I'll post something late tonight hopefully.

[atoff]

Yeah, the gap is what dissuaded me from the cap. I like your design... it looks like it already has two adjustment screws, no? I'd think it would definitely need two. In any case, look forward to seeing the result. My belts are in need of tightening right now... layers are looking very off, and the belts feel a little too loose. Oh, also, looking at your pics, it loos like it might jut too far out against the acrylic, I would think about putting a curve on the side facing out.

[esbowman]

Sorry. Should have clarified that I'm thinking about utilizing two adjust screws per side. Right now my design just uses one hex screw to adjust up and down, and my fear is that if for some reason the yellow screw cap/bottom were to move a bit the whole tensioner bracket could rotate forward or backward. I don't THINK it would, but I might as well make it beefier to make sure it does not. I don't want to release something to everyone unless I know it's functional and foolproof.

Regarding it sticking out too far, no worries there. I simply placed it on top of the melamine base and it's not installed. It definitely will clear the acrylic cover by 1-2 mm. Good eyes though Hawkeye.

[esbowman]

Here's a version 2 prototype. Let me know what you guys think.

A couple of things I noticed will need adjusting.

1) There's a cable tie on the right side of all my towers that grasp the wires that exit the top of each tower. I think I would need to either add a cable tie slot in my screw bottom pieces, or just move the adjustment screws a little further away from the towers. This would provide a small gap and allow it to fit over them.

2) There's a stop screw for the extruded aluminum towers on the left side of each melamine tower support. This gets in the way with this design as well. Again, I think I can just move the adjustment screws away and leave a small gap.

3) I'll end up making the nut capture area more substantial so it's easier to install. Right now it's so shallow that it's a little difficult to press them in place. This is the area for the #6 32 nylon lock nuts for the screw that goes through the bearing. Not the adjustment screw nuts.

The good news, is that I think this design works much better. Haven't installed it yet, because I know it's not ready for prime time but this seems like a much more solid design. Pics below...for whatever reason my printer decided to get sloppy tonight.

Top view

Bottom view with adjustment screw base/bottoms detached

Right side view

Left side view

[barnett]

I don't have a V2, but I think that looks good. The double screw version seems preferable so it pushes on the melamine over a wider area - as long as there's enough room for it.

There's probably a break in period for these belts because in the beginning I fiddled with it a lot and now I probably haven't touched them in over a year.

[atoff]

Nice...looking good. I think the two adjustment screws per side is the way to go.

[geneb]

I like the original design better - I'd use one screw, but use a wider, rectangular foot for the adjuster screw. Same effect, fewer parts.

g.

[Eaglezsoar]

I like the original design better - I'd use one screw, but use a wider, rectangular foot for the adjuster screw. Same effect, fewer parts.

g.

I tend to agree with Gene after seeing both, perhaps you can offer both and let the user decide which one he wants to use?

[esbowman]

The drawback to the first design in my opinion is that it doesn't allow for as much adjustablility when compared to the two screw design. By separating the two screws I'm able to gain 1-2 mm by moving their respective nut captures up a bit. I hope that makes sense. That said though, I do agree that less is more in this situation. I'm all about keeping it minimal . I'll tweak the first one again with a wider foot and see what you guys think. Thanks for all the feedback.

[esbowman]

After spending today tweaking the first design, I'm just not happy with it. Seems that it will be tougher to install and I think having two screws on each side will indeed keep the pressure lower on the melamine overall. I might offer up the first design later, but for now I'm going to knock out the two screw version. Printing another iteration of it with the adjustment screws offset from the melamine panel by 4mm. This should keep it from hitting the cable ties and tower top screws on each side. My Z-axis belt feels a bit looser than the others so I'll probably install this tonight and put it to good use.

I'm currently having a hell of a time calibrating my extruder to accurately print within the specs of my model. Do you guys have any hints, or links to help me calibrate this? I tried a test 20x20x10 cube and it's measuring about 1 mm too small overall.

[apostoly]

Very Interested in this, Looks good!!

Paul.

[esbowman]

Just an update. I'm up to version 15 on this. Lol. Trying hard to get something that provides easy adjustability, full adjustability, and still allow us to use the acrylic covers that ship with it. I'm printing one now that hopefully will be good enough to let you all test. One caveat is that you'll likely need to order some thumb screws or cut off a hex wrench to allow for adjustment if you use socket cap screws. My hex wrench is just too big. I found a source on eBay and ordered some spade thumb screws #8 32 1" length. Bought 25 for roughly $8 or $9 shipped. http://www.ebay.com/itm/331133117348" onclick="window.open(this.href);return false;

I think they will make it very easy to adjust, but want to test them first before recommending. Hope to have something soon.

[esbowman]

Well, back to the drawing board. I'm to the point I can't make the two screw version fit without it getting in the way of the decorative acrylic panel that fits there. There's just not enough room. I have to keep the adjustment screws away from the vertical melamine supports enough so that they clear the cable tie and tower stop screw on each respective side. If I go smaller, the nut captures will likely be too weak. I'm back to going with Gene and Eaglesoar on the one screw design, but my big issue with that is:

1) It seems even with a wider foot it will end up putting more pressure in one area...probably not enough to worry about and I'm being paranoid.
2) This is more important to me and possibly a deal breaker. With the adjustment screw directly in front of the screw that holds the top bearing, it makes it impossible to adjust the height THEN tighten the bearing screw. The adjustment screw ends up getting in the way.

I'm almost thinking a cap is the way to go, or perhaps finding a way to replace the horizontal tower support brace that is tapped for the nylon thumbscrews at top. Totally open to suggestions at this point.

[geneb]

You could not worry about it at all. I've never seen it as an issue.

g.

[esbowman]

LOL. GENE!!!

Am I creating a solution for a problem that doesn't exist? haha. I personally had a heck of a time getting all of the belts tensioned the same amount. I just felt it would be better to have something that was adjustable in small increments as the belts loosened over time. Maybe I'm stressing about it for nothing.

[gajtguy]

Aw man, I liked watching this thread. Making little brackets and stuff. Keep working on it.. I think the "axle" screw is holding on for dear life to keep tension on the belt. It's working in Shear using the "out of the box" instructions. Which makes me think it'll move over time, no question.

How about a wedge design? You could have a single screw face out on either side of tower. Of course it wouldn't stick out though. The screw would pull in a wedge on either side raising a "block" with the axle screw vertically. With wedges on both sides you could get a really fine adjustment. Plus once it's locked in, the axle is basically resting on something. Very small chance of a drifting loose.

What do you think?

[esbowman]

No worries. I plan on working on it, because quite honestly it's become a challenge at this point. lol. I'm a problem solver at heart, and I'm kind of OC on things like this. I had my Z tower belt get loose mid-print. I know it worked it's way loose during that print because it was tight before I started it. Perhaps I didn't tighten it enough when I built it, but regardless I don't want that outcome again. All of the 15-16 revisions so far have had one issue or another that makes me rethink the design. I'll live by Thomas Edison's words though,"Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time."

To your idea, I hate to admit that I'm not following you. Can you sketch it up quickly? Explain it a bit further? I appreciate any ideas I can get. Something will click eventually...I know.

[gajtguy]

Ok. So here's what I was thinking with the "ramp" axle tensioner. Please, you real engineers pop in here and clean this up. I'm only a fake engineer.

Essentially, you've got the Blue fixed block that goes on either side of the tower. It's even got a cutout to avoid the wire tie and screw that aligns the top plate to the top of the alum tower post. (not visible).
The black vertical block, shown better in the 2nd picture, just shows the approx travel range that is laser cut in to the tower piece of melamine.
Then the Green block with the axle running through it. This will raise or lower to add tension to the belt.
The tension is adjusted by the bolt going through the pink block. As you tighten the tension bolt, it pulls in the pink block toward the blue block and that pushes up on the green block. Once you have it dialed in, the axle will now rest on these blocks. This should require very seldom adjustments and should hold everything in place real nice.

Anyone see any glaring issues with this?
.
.

[Eaglezsoar]

How is the green part supposed to go up when it is held captive by the adjusting screw?

[esbowman]

I like the idea, but I'm afraid you don't have enough room from the center point of the bearing screw to the outer wall of the blue block and that adjustment screw. Hard to tell unless we have dimensions. Eaglesoar has a good point too. I appreciate the brainstorming, and altering your design could possible work if there's a way to make it all fit.