Soft Neato rollers

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Soft Neato rollers

Postby humanoid » February 9th, 2016, 3:24 am

Didn't have much success using heat shrink on the rollers. On the back (the bigger rollers) it wouldn’t go back in, and in the front the shrink wrap lasted 5 full house cleanings before it wore out and disintegrated.

Got 19mm silicon beads for the big rollers instead. The original dimensions are 18x20mm, so 19mm wide is a tight fit. The gap is very tight, but it barely fits. The problem is the hole in the bead is very small. I assumed I can drill it, but the bead just stretches on the drill. So I pressed the axle into the silicon, its very tight so the axle spins with it. The bead and axle are locked.

One side rolls smoothly, the axle spins in the case. In the other side the axle is not spinning in the case (I assume that's the way it should be, the roller should spin on the fixed axle).

So failed again. I think the axle spinning in the case will wear the case.

Any ideas about how to drill the silicon bead? Or how to make one? One idea I had is to insert a plastic tube into the silicon bead, so the tube will spin on the axle. But this will stretch the bead more and it will probably not fit. There is barely space now.
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Re: Soft Neato rollers

Postby glnc222 » February 9th, 2016, 4:48 am

Related thread "No More Clack-Clack" http://www.robotreviews.com/chat/viewtopic.php?f=20&t=16794&hilit=clack

Cut a strip around the center off with a knife to reduce the diameter. Maybe squeezing it between washers with a bolt through it. I doubt it can be sanded down spinning in a drill.
It could be spun in a drill against a hole saw.

Make a hole wide enough for metal tubing.
A hole through it must be cut with a punch-like tool instead of drilling, where it just deforms around the bit. A metal tube could be spun in a drill and maybe work as a hole saw. There may even be small hole saws.
Or heated with a soldering iron or gun (actually a tool used to desolder around wires).

Wood Dowel and O-Ring
What I would do in absence of a 3D printer is take plastic rod sections or even hard wood dowel, drill a 5/32 in. hole through for 4mm shaft, bolt into a drill and spin the edges against a rasp to shape, and add a groove for an o-ring (spin against a saw). To drill a straight hole through first put a straight hole through flat wood with a drill guide, then press the flat end of the dowel against the block used as guide. Corner between two blocks can substitute for a drill guide.
5/8 in. dowel 16mm, 3/4 in. 19mm needs sanding down. In Home Depot, hardware stores.
No bushing needed. Self-lubricating. Easily shaped with rasp, file, sanding.
The inventor of the marine chronometer once made clocks of wood for the self-lubricating and strength properties.

You could order 3D printing from online services. They have been printed in Germany but I did not get the files, maybe could ask more. Should not be hard to CAD.

For the front, what about metal tubes inserted into sections of plastic tubing?
Last edited by glnc222 on February 11th, 2016, 2:10 pm, edited 2 times in total.
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Re: Soft Neato rollers

Postby glnc222 » February 9th, 2016, 5:03 am

Related to plastic tubing is insulation on thick wires.
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Re: Soft Neato rollers

Postby CleanMe » February 9th, 2016, 12:20 pm

To enlarge the hole you might try heating something like the blunt end of drill bit with a high heat source (torch, kitchen range, etc.) and pushing it through the hole. The size of the drill bit should determine the final size of the hole.

Of course the heat will end the useful life of the drill bit and you'll want to do this in a well ventilated area, preferably with your nose upwind.

A silicone surface spinning on a metal axle may create too much friction. You may need to glue a metal tube in the enlarged hole. The axle would then be inserted through the metal tube.
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Re: Soft Neato rollers

Postby vic7767 » February 9th, 2016, 3:31 pm

Here's an option that was considered just after the first XV-11s were out:

It entails turning down the rollers and cutting a groove into the flat portion and installing a small neoprene O-ring.
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Re: Soft Neato rollers

Postby glnc222 » February 9th, 2016, 4:24 pm

Rubber Molding

Those beads are made by molding process. Moldable rubber is carried by The Container Store and others:

[url]http://www.containerstore.com/s/need-it/problem-solvers/sugru-self-setting-rubber/12d?productId=10035849&ci_src={ifpla:17588969}{ifpe:27500988}&ci_sku=10062358&srccode=cii_17588969&cpncode=37-151717310-2&utm_source=channelintelligence&utm_medium=feed&utm_campaign=google[/url]

A hole in some wood covered with grease might make a cylindrical mold. Insert bronze bushings or metal tube bearing for shaft.

Sounds cheaper to machine a hard material and cover with o-ring.

Other brand robots have rubber tread casters.

If you look into a printer see small rubber rollers used to feed paper. You can probably buy rollers in any size in quantity custom orders. Scavange junked copiers and printers.
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Re: Soft Neato rollers

Postby glnc222 » February 9th, 2016, 5:03 pm

Rubber Stoppers

When I reproduced the rubber brush mounts for ball bearings from Vic (another thread) I cut down sections of rubber bottle stoppers in Ace Hardware.
It can be spun in a drill and filed to flatten and cut with knives and hack saws.
It can be drilled just with a larger diameter than the ending hole.

Maybe those beads above are similar.

Ace also has a variety of nylon spacers alternative to metal tubing bearings.
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Re: Soft Neato rollers

Postby humanoid » February 10th, 2016, 1:50 am

Maybe something like this with spacers on both sides

http://m.alibaba.com/product/6029789921 ... oxide.html

Shower door rollers seem to be the right size, but they are made of nylon and not soft materials.
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Re: Soft Neato rollers

Postby glnc222 » February 10th, 2016, 4:02 am

Seems same size as a window sash weight pulley at Amazon http://www.amazon.com/Plastic-Single-Roller-Sliding-Window/dp/B00G9BSTZC
Sold in a metal bracket.
Hole Dia. : 3.8mm/ 0.15";Roller Size : 18 x 4.8mm/ 0.7" x 0.19" (D*T)
Hole is over 1/8 in. sounds too big, similar to main brush shaft.
Could be in hardware stores given the application. Also sliding door rollers.
Alibaba is for industrial quantities. Try Aliexpress.

Thought a soft material was sought? No luck machining the beads?

Nylon Spacers
In English measures, I used 1/4 in. OD #4 screw nylon spacers for side brush motor mount. 2.8mm hole. Other sizes available. #6 screw 3.55mm (M3 screw). So vinyl plastic tubing comes 1/16 in. thick walls in ID's 1/4, 3/8, ... with OD such as 3/8, 1/2 and 5/8 -- 18mm. 3/4 in. 19mm OD. Three concentric layers 1/8 in. total two walls each, goes from 1/4 ID to 5/8 OD. Layer sizes onto the nylon spacer, cut to desired length. Sold by the foot in Ace Hardware so small order, and Amazon.
Also a trick of wrapping tape several times around shafts and spacers to widen and fit tight.
I do not have the shaft size of the Neato roller.

[edit] It may also be possible to layer nylon spacers and cut groove for an O-ring. Lots of sizes.
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Re: Soft Neato rollers

Postby drfish » February 10th, 2016, 6:40 am

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Re: Soft Neato rollers

Postby glnc222 » February 10th, 2016, 2:54 pm

Great insight -- maybe all sorts of toy cars and trucks, models. There might be some nylon sleeves and bushings to adapt the shaft diameter if needed. Unless the 18mm is the wheel thickness and 8mm is the shaft...
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Re: Soft Neato rollers

Postby glnc222 » February 10th, 2016, 6:35 pm

More Lego

Many wheels and rims made by Lego http://www.brickowl.com/catalog/lego-parts/vehicle/wheel
This rim 18 x 14 mm might work with O-rings http://www.brickowl.com/catalog/lego-wheel-rim-18-x-14-with-pin-hole-20896-55981-57754
The tires made for it are 24mm or wider, too big -- but not the o-ring...
4.8mm hole might be drilled wider to fit a 5mm OD M2 nylon spacer for bushing. Less than 1/100 in. difference.
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Re: Soft Neato rollers

Postby humanoid » February 10th, 2016, 11:25 pm

The steel roller axle on the XV is 4mm, worth mentioning.
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Re: Soft Neato rollers

Postby glnc222 » February 11th, 2016, 12:46 am

Copper tubing Ebay http://www.ebay.com/itm/Albion-Alloys-ROUND-COPPER-TUBE-Metric-range-in-305mm-lengths-Precision-Metal-/131273547312?var=430554406935&hash=item1e90835e30:m:mGTN5W7ozCdp66ViPcLG6Yw

Tubing CT4M 4mm ID to fit shaft, 4.9mm OD to fit the Lego rim above for o-ring. Haven't checked O-rings.

or better, self-lubricating sleeve bushings 4 x 6 mm -- drill out the wheel slightly. 6 mm length, need two.
http://www.ebay.com/itm/10pcs-SF-1self-lubricating-composite-bearing-bushing-sleeve-4mm-6mm-6mm-/290639990172?hash=item43ab7e4d9c:g:JX4AAOxyhodRry3C

Also usable with those beads.
The shaft sounds similar to the main brush shaft, for which bushings are made used in the rubber mounts -- similar to above, some coming with flanges etc. Might want flanges at sides of wheel.

Takes a while to get from China.
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Re: Soft Neato rollers

Postby humanoid » February 11th, 2016, 1:00 am

Got some nylon spacers, they are basically tubes with 4.5mm ID and 6.4mm OD.
The silicon ball is so flexible I can force them into the 2mm hole. But then it gets even wider (19.5mm) and does not spin at all in the Neato.

Tried sanding the balls by putting them on a cordless drill and spinning against sand paper. They barely sand. Finished a couple of rechargeable batteries on the drill with almost no change. Silicon does not like to be sanded. I think with a cord drill that is faster and lasts longer I may be able to do it. Need to remove about 1mm diameter.

But at least it looks possible now.
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Re: Soft Neato rollers

Postby glnc222 » February 11th, 2016, 1:29 am

Drilling beads with a large bit might let them not expand as much. Vic widened the hole in the rubber brush mounts with a Dremel Tool rasp cutting head.
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Re: Soft Neato rollers

Postby humanoid » February 11th, 2016, 2:20 am

I tried drilling the hole, didn't work. The silicone just stretches over the drill bit.
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Re: Soft Neato rollers

Postby glnc222 » February 11th, 2016, 2:43 am

I guess that's why Vic used a Dremel cutter. You could chuck the bead into a Dremel for ultra high speed sanding.
The bottle stopper material seemed workable. I would also use a knife on the bead and then smooth it rather than just sand. I also used a file I think instead of sanding. Wrap it in masking tape marking boundaries of strip to slice off helps guide knife, like peeling an orange. Sawing motion.
Maybe why the o-ring is best. Or mold your own rubber to proper size.
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Re: Soft Neato rollers

Postby humanoid » February 20th, 2016, 12:47 am

Finally got it to work. Got a power drill (not cordless) and coarse sand paper, took a while but I got it to the right size eventually.

Got two nylon spacers in a hardware store, cut to size and force into the tiny hole. 6mm tube fit into the 2mm hole, and now it spins on plastic and not on silicon, so very little friction. Much quieter.

Next I will do the front rollers, I can hear them now when the robot goes back to charger and the brush is off.
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Re: Soft Neato rollers

Postby glnc222 » February 20th, 2016, 2:02 am

Congratulations. Photos of final beads with bushing would be nice.
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