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PStechPaul
03-08-2015, 12:17 AM
I am planning to add a small DC motor to my air motor project so that I can use it as a generator and also possibly as a pump by applying voltage to the motor. I want to use a rubber or flexible plastic drive belt but I don't have the right size. However, I have some longer belts that I thought I might be able to cut to size and glue the ends. I've tried this with regular "Super Glue" Cyanoacrylate but with limited success. This system is supposed to glue polyethylene and polypropylene and other difficult materials, so I thought I'd risk $6 at Walmart for a tube:

http://enginuitysystems.com/pix/tools/Loctite_Plastic_Bonding_1765.jpg

It has an activator/primer with a felt tip that is applied first, and then the glue is applied to one surface and then put together to bond in 30 seconds. I applied the glue to both ends and let it bond, and it seemed to hold pretty well:

http://enginuitysystems.com/pix/tools/Loctite_Plastic_Bonding_1766.jpg

http://enginuitysystems.com/pix/tools/Loctite_Plastic_Bonding_1767.jpg

I pulled on it with probably 5-10 pounds of force and it held. I tried it on a 20 pound SLA battery and it finally broke, but for my purposes it should not need to handle more than a couple pounds. Here is approximately what I want to do:

http://enginuitysystems.com/files/CAMM112/Wobbler_with_motor_NE.jpg

The belt I show above is a 1 mm pitch drive belt from a junk HP inkjet printer/fax/scanner, but I also have some slightly wider 2 mm pitch belts made of a more rubbery material (Subaki 440P2M4). I also have some plastic (and maybe a few metal) pulleys I may be able to use, although I'd rather machine a groove in the flywheel as shown. I'm not sure how I'd make the cogs, although I thought I might be able to drill a series of holes at the 2 mm diametrical pitch, and then machining the surface to reveal the cogs. Maybe a small V-belt or a large O-ring might work OK.

atty
03-08-2015, 12:52 AM
There is a seller on Ebay that will make a urethane belt in any length and quite an array of diameters, should you decide to go that route.

On the flat belt side of the problem, I might suggest that you make your "45" horizontally, rather than vertically as shown. Simply run both sides of the flat belt on a sander until you have achieved a suitable 45, or at least until they mate together reasonably well. This will give you considerably greater contact surface, and thus strength. Needless to say, they have to be clamped tightly for the set time.

PStechPaul
03-08-2015, 04:26 AM
That's a good idea for making the joint. Here is an image of a 72 tooth 2 mm pitch pulley made by drilling holes and machining the 2" disc to 1.75" with a 1/4" wide groove.

http://enginuitysystems.com/files/CAMM112/Timing_Pulley_2mm_72_tooth.jpg

mickeyf
03-08-2015, 12:23 PM
There is an old thread here somewhere that discusses gluing automotive serpentine belts as an alternative to a leather flat belt. My take-away from it was that methyle methacrylate was the best adhesive for those, but I have been utterly unable to find it where I am. Also mentioned was Loctite 85265, which either does not exist, or is hiding from me. I have not even been able to find the loctite product shown here in local stores. The automotive belts have internal re-inforcement and are not especially flexible - they may be a very different material than yours.

Rosco-P
03-08-2015, 01:20 PM
Try a vacuum cleaner and sewing machine repair store for belts. Or just order the belt you want from a place like Motion Industries.

Forestgnome
03-08-2015, 01:37 PM
You could use polyurethane belting. Just heat the two ends against a hot piece of steel, then push the ends together. Trim excess with dykes or grind off. I just made some belts for my Themac grinder using this stuff and it works great. The same company that makes this stuff also makes v-belts of the same material.
http://www.mcmaster.com/#flat-drive-belts/=w803oa

brian Rupnow
03-08-2015, 04:39 PM
Paul--Use a rubber o-ring. That's what I use on nearly all of my engine driven projects.

PStechPaul
03-08-2015, 05:06 PM
The round urethane belt material might be the easiest way to go for small drives such as this. The mating grooves on pulleys are easy to machine, and the belts seem to be easy to cut and join. I also looked into small pitch timing belts and pulleys, and the components are rather expensive and difficult to machine, but I already have some components I can re-use. Another possibility is miniature acetal roller chain, which snaps together in any length. It is also not cheap, but sprockets can be made more easily than timing belt pulleys.

A good source for small drive components is SDP. They also have 1mm and 2mm pitch components, reasonably priced, but I would like a ratio of 10:1, and mostly I have found a maximum of 6:1 and maybe 8:1.

http://www.sdp-si.com/eStore/CoverPg/Drive_Components.htm

[edit] Using their pulley and belt calculator, (https://sdp-si.com/eStore/CenterDistanceDesigner) I found that they do have suitable parts, but a 10 tooth pulley at a 2" center distance to a 100 tooth pulley has only 3 teeth in mesh. So I may need to settle for a smaller ratio, or use an idler pulley.

I have an old fax machine I may raid for parts. I got lots of stuff from the HP 4 in 1 machine, particularly shafts, gears, and a couple of small motors, and the glass plate might be flat enough for use as a poor man's surface plate. Plus I was able to figure out how to connect the scanning light bar with three color LEDs. I can connect it to a PIC and make a cool light display. Maybe I'll connect it to this motor/generator. :cool: