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General Renewable Topics => Off-Topic => Topic started by: acresswell on December 22, 2015, 07:52:19 PM



Title: machining down a nylon / polypropylene wheel
Post by: acresswell on December 22, 2015, 07:52:19 PM
For a mad project I'm planning (a rotary sieve/ trommel to separate out the stones from our veg plot), I need about 8-10 fixed castors with wheels that are about 12mm wide.  I can't find any, so I'm thinking about using ordinary castors like http://www.screwfix.com/p/fixed-castors-swivel-50mm-pack-of-4/69497 (http://www.screwfix.com/p/fixed-castors-swivel-50mm-pack-of-4/69497) and then turning down the outer edges of the wheels.

I don't have a lathe, so I'm wondering whether I stand a decent chance of success if I clamp a wheel between washers/nuts on a piece of studding, and hold the studding in a drill that's clamped to a bench...

Will an ordinary wood chisel do the trick? I can rig up something to lean it against so that the chisel isn't flapping around in the air...  I can also re-grind it to whatever angle would be best...  Alternatively I have an old cold chisel that's about 18 inches long (so it might give me more control) and I could have a go at grinding it to give a sharp edge...
Would it be better to hold an old plane against the wheel?

Will I have a better chance with nylon or polypropylene wheels? 
The other possibility is rubber wheels, but I'm suspicious that the chisel will just dig in or rip chunks out of rubber rather than cutting...

I'm thinking of wheels somewhere between 50mm and 100mm diameter.  Obviously if I use smaller wheels I'll have to remove less material.  Larger wheels would be better for the project (but also more expensive). Will one size be easier to machine?

I have a choice of 2 drills - a mixer one which is 2-speed but turns relatively slowly with high torque, or an old hammer drill (with broken reversing switch, but the variable speed still works) which turns much faster.  I'm not willing to risk my "best" drills!  Which speed will give me the best chance of success?

Any/all thoughts appreciated!


Title: Re: machining down a nylon / polypropylene wheel
Post by: knighty on December 22, 2015, 07:59:23 PM
I'd clamp/screw the bracket down to a bench, then let them spin while I sanded them down with a flap wheel on an angle grinder

they'll spin fast enough that they'll end up nice an even, plus it's easier and you should have more control


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on December 22, 2015, 08:10:22 PM
Knighty, do you mean one of these?
http://www.screwfix.com/p/erbauer-zirconium-flap-disc-115mm-80-grit/7448G

Like the idea of doing it without disassembling the thing.  I could stick a bit of scrap wood in the vice and bolt the brackets to it...

Thanks


Title: Re: machining down a nylon / polypropylene wheel
Post by: knighty on December 22, 2015, 08:49:33 PM
yep one of those :-)


probably a good idea to oil the bearings in the center of the wheel a bit before you do it too, they might not have much lube on them when they come!



Title: Re: machining down a nylon / polypropylene wheel
Post by: smegal on December 22, 2015, 09:38:12 PM
What about using scooter or rollerblade wheels. They have an ID of 8mm so you can just make the axles as required to support the trommel


Title: Re: machining down a nylon / polypropylene wheel
Post by: roys on December 22, 2015, 11:17:26 PM
Send them to me and I will stick them on my lathe and turn them down for you if you want.


Title: Re: machining down a nylon / polypropylene wheel
Post by: Nickel2 on December 23, 2015, 12:38:56 AM
Silly question time.  ;)
Do they need to be 12mm wide, or can you amend your design to suit a ready-made item?
I'm a firm believer in repurposing ready-made items with the minimum of modification, so if one breaks or fails, you just buy another box of 4 and swap out the broken one without having to do any mods.
Can you post a pic of a scribbled drawing?

N2


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on December 23, 2015, 03:12:52 AM
Silly question time.  ;)
Do they need to be 12mm wide, or can you amend your design to suit a ready-made item?
I'm a firm believer in repurposing ready-made items with the minimum of modification, so if one breaks or fails, you just buy another box of 4 and swap out the broken one without having to do any mods.
Can you post a pic of a scribbled drawing?

N2

I think the wheels do need to be 12mm wide, because I'm matching ready-made items that are harder to modify (cycle wheel rims).  The rim (with spokes removed) forms the shape of the trommel drum. The castors then run inside the rim to hold the drum in the right (horizontal, with a slight downward slope) position.  The trommel probably needs to run for about 2 days to sieve all the soil in my veg patch, then it will probably be taken apart in any case, so as long as the castors last for about 10 hours of operation, I'll be happy.

There are various examples on youtube, like this one:
https://www.youtube.com/watch?v=le-Nmg0q9jE (https://www.youtube.com/watch?v=le-Nmg0q9jE)

There are couple of people hiring out the proper scheppach rotary sieves (on ebay), but I can't find one locally...

The only other thought is whether anyone can suggest where I can get 2 old mountain bike rims, which would be a bit wider and take the unmodified castors.  I tried a couple of local bike shops with no luck. Have kept my eye on ebay, but the only bike wheels being sold seem to be rather higher spec (and price) than I need. Have even looked on ebay for a scrap bike, but nothing suitable has come up locally. The blokes at the tip were quite aggressive when I enquired about a bike wheel from one of their skips... !

The rims I have came from my sister's garage - they were hanging there when she bought the house, but unfortunately they're from a racing bike so they're a bit narrow.


Title: Re: machining down a nylon / polypropylene wheel
Post by: DaveF on December 23, 2015, 09:03:07 AM
Try the link below. I know the wheel has a 35mm thick edge but this is just a 'lip'. Might be easier to take a wheel similar to this and use a 70mm hole saw in line with wheel the axle will go through and just saw a slightly smaller and thinner wheel out of the hub material.

http://uk.rs-online.com/web/p/solid-wheels/0387919/

Regards,

Dave


Title: Re: machining down a nylon / polypropylene wheel
Post by: smegal on December 23, 2015, 09:34:14 AM
You really are best off using something like this:

http://www.ebay.co.uk/itm/291504984328?

Where abouts are you? I have a couple with badly drilled holes in the side that you can have.


Title: Re: machining down a nylon / polypropylene wheel
Post by: smegal on December 29, 2015, 11:28:22 PM
If you're still looking, drop me a PM and I'll send a few wheels your way.


Title: Re: machining down a nylon / polypropylene wheel
Post by: guydewdney on December 29, 2015, 11:40:15 PM
i have a fully built vibration table, that we used for soil sieving. just a frame with some mesh on it, and a motor with an offset weight. v simple to build.

its in somerset.....


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on December 30, 2015, 08:33:12 PM
If you're still looking, drop me a PM and I'll send a few wheels your way.

Smegal,

thanks for the kind offer.  Having raided my Dad's garage junk store, I think I'm now ok for the smaller wheels/castors.  I reckon the ones I've found were some of the first prototypes made by the bloke who invented the wheel, but the size is right!

Thanks again



Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on December 30, 2015, 08:47:50 PM
i have a fully built vibration table, that we used for soil sieving. just a frame with some mesh on it, and a motor with an offset weight. v simple to build.

its in somerset.....
Thank you, Guy.

Unfortunately, I'm a fair way from Somerset, and I'm not convinced that a vibrating table design will work for us.
I looked at vibrating table designs before deciding to go for a trommel instead... a test run with a sieve suggests that more than 50% of our "topsoil" is really gravel, so I'd end up emptying the vibrating frame after every bucketful.  A trommel is undoubtedly harder to build, but the process can run continuously rather than in batches.

Thanks again

PS
The gravel that is separated out will be a useful by-product-- I'm going to use it to form the paths between the raised beds.  Any excess will get dumped by the trailer load onto a boggy bit of track. Luckily there's no shortage of soil to process... we live on quite a steep hill, so the vegetable patch needs to be terraced as I go along, and of course I don't care if the paths between the raised beds don't have any topsoil under the gravel.  If we already had flat land, I'd probably be thinking about just importing some decent topsoil, but since I've got to dig it all anyway to make it vaguely flat, it seems sensible to try and get some useable soil at the same time.  Getting imported soil up the hill wouldn't be easy, either!


Title: Re: machining down a nylon / polypropylene wheel
Post by: mike7 on December 30, 2015, 11:47:58 PM
I made a rotating sieve last year to clean up the muddy gravel on my driveways. it worked a treat. I didn't need any wheel rims or castors for it as I had a central shaft and just a few spokes to support some curved metal flats - the equivalent of your rims. I'll see if I can get and post a photo in case it's any help. For sure the design of such things depends very much on what you happen to have available to you, though.


Title: Re: machining down a nylon / polypropylene wheel
Post by: guydewdney on December 31, 2015, 09:01:09 AM
the table is set at an angle, and the detritus works its way off the end..... about 10 degrees


Title: Re: machining down a nylon / polypropylene wheel
Post by: fourfootfarm on December 31, 2015, 02:09:28 PM
Gumtree is awash with tatty second hand bikes, they're good in terms of having a ready supply of nicely sized tube and bearings etc to hand.


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on December 31, 2015, 07:15:58 PM
Gumtree is awash with tatty second hand bikes, they're good in terms of having a ready supply of nicely sized tube and bearings etc to hand.

Thank you.  I'd already tried ebay and preloved.  Had a look on gumtree - nothing suitable locally at the moment for less than £20.  Think I'll just have to be patient or increase the budget!



Title: Re: machining down a nylon / polypropylene wheel
Post by: fourfootfarm on January 01, 2016, 07:37:41 PM
how many wheels do you need? Just two? Do they have to be 100% straight?

You could try asking around your local bike shops, quite often when they replace peoples wheels they just chuck the old ones away. If you only need the rims it doesn't matter if the hubs and spokes are knackered.


Title: Re: machining down a nylon / polypropylene wheel
Post by: mike7 on January 01, 2016, 10:47:12 PM
Here's my slightly rickety sieve. I guess you wanted to leave the mouth of the drum quite open, hence the need for castors, but I found this arrangement to be good enough. I was sieving gravel with some soil in it - if it is more soil than gravel then it would need to be dryish in order not to bung up the mesh.

(http://s18.postimg.org/6bqs9cndx/IMG_2132.jpg) (http://postimg.org/image/6bqs9cndx/)

(http://s18.postimg.org/609bwl6xx/IMG_2134.jpg) (http://postimg.org/image/609bwl6xx/)


Title: Re: machining down a nylon / polypropylene wheel
Post by: fourfootfarm on January 02, 2016, 09:42:57 AM
All of this is giving me flash backs to a time when I worked for a recycling company and ran one of these. If they stuck too much wet soil in the hopper the trommel would get bunged up and you'd have to dig it out with a shovel. Not much fun. Especially when it was big enough to stand in but only at a crouch.

I don't miss that job.


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on January 05, 2016, 06:33:18 AM
Here's my slightly rickety sieve. I guess you wanted to leave the mouth of the drum quite open, hence the need for castors, but I found this arrangement to be good enough. I was sieving gravel with some soil in it - if it is more soil than gravel then it would need to be dryish in order not to bung up the mesh.

Looks really good.  Unfortunately I don't have a welder, so my options are a bit more limited...that's why I'm going for castors round the outer edge of the rims, held inside a wooden frame.

Luckily, even after the recent downpours, my soil is pretty dryish.  Living near the top of a hill with gravelly soil does tend to help the drainage! 


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on January 05, 2016, 06:46:27 AM
 :fume
All of this is giving me flash backs to a time when I worked for a recycling company and ran one of these. If they stuck too much wet soil in the hopper the trommel would get bunged up and you'd have to dig it out with a shovel. Not much fun. Especially when it was big enough to stand in but only at a crouch.

I don't miss that job.

Sounds horrendous... glad mine is on a slightly smaller scale / won't have a hopper!


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on April 16, 2017, 10:00:57 PM
Have finally managed to get round to building the rotary sieve/ trommel after well over a year of scavenging bits/pieces and tripping over them.

It's great!  Even better, my kids love it so they spent much of today loading in the big pile of soil, just calling on me when the wheelbarrows needed emptying.
Raised beds in the flower garden filled today and the veg patch should be up/running by the end of the week...
Even SWMBO is impressed!

A few hints for anyone else who might be thinking about making a rotary sieve:

1.   Make sure all your wheel rims are roughly the same size.  It’s theoretically possible to have a cone shaped drum, but it’s much harder to get it aligned and working reliably. 

2.   Use mountain bike rims.  They’re wider than racing bike rims.  Unless you use tiny castors, most castors are too wide to slot inside mountain bike rims and it’s a lot of hassle to cut/file them down. I ended up throwing away some 700c racing bike rims and buying some 26” mountain bike rims because it was easier then messing about with the castors

3.   The earlier you start collecting bike rims, the cheaper it will be.  If you can’t find any free ones, look on ebay for 99p “spares or repairs” bikes, or in the recycling bit of your local waste site.  It can be cheaper to buy a whole bike and throw away the frame.  My first set of wheels was free.  My 2nd set cost 99p for the whole bike.  When I decided at the last minute that I needed a 3rd set that matched, they cost £10.50 but I could pick them up the same day...

4.   Most weldmesh comes in 36” width and this is plenty if you have sandy soil.  I used 48” mesh because I had some, but most soil falls through the sieve in the first 18” so the extra 12” just makes my device less portable.

5.   If you use 36” mesh, I reckon you’d get away with just 3 bike wheels (18” apart).  I used 4 wheels on my 48” mesh, so they are 16” apart.

6.   10-12mm mesh gives a lovely fine material.

7.   Make sure you’ve got plenty of cable ties – it takes more than you think to fix the mesh. 140mm ties aren’t quite long enough to form a loop through 2 adjacent spoke holes – I used about 130 cable ties (200mm long). A pack of 100 should be enough if you’re using 36” mesh and only 3 wheels.

8.   200mm cable ties are usually 4.5 or 4.8mm wide, but these are a tight fit through the spoke holes, so worth running a 5mm drill though each hole to make your life easier

9.   If your arms aren’t long enough to reach the inside of the middle of the drum (less likely if your drum is only 36” long) then persuade a small child to stand still.  Lower the drum down over their head, and they can help to push the cable ties back to you.

10.   Tumble dryer motors are easier to use than washing machine motors – they are designed to go at a slower speed so you probably won’t need to worry about speed control or extra gearing/pulleys. If you’re scavenging a motor, get the belt, too. Don’t forget the capacitor for the motor.

11.   Do put at least two castors (one at each end) over the top of the drum, to stop it lifting off the lower castors/ to keep the belt tight, but think about how you will be able to remove these castors easily later if you need to get the drum out.

12.   Use the flat drive belts (like on tumble dryers) rather than a v-belt – they’re better at gripping the outside of the wheel rim.

13.   Remember to mount the motor on top of the sieve, not underneath (where it will get full of dirt!)

14.   Think about how you will cope when the belt stretches.  I just mounted the motor on a big bit of wood that was attached to the main frame with 2 long screws.  As the belt stretched slightly in the first hour, I loosened the big screws and put packing pieces underneath

15.   Think about electrical safety and stopping the motor if something jams.  I used a waterproof light switch (motor is only 1.2A and the light switch is rated at 10A, so even if there’s a bit of surge on startup, it should be fine).  Don’t be tempted to rely on pulling the plug out of the extension lead quickly enough. Do connect an earth wire to the motor case. Make sure connections are insulated.

16.   Think about how you’ll keep the motor/electrics dry if it rains and you can't be bothered/don't have space to lug the device inside.  I used a small tarpaulin, with a bit of bungee cord on each corner to clip onto the 4 screw hooks placed strategically.

17.   Make sure the legs are long enough so you can fit your wheelbarrow underneath, but keep the height as low as possible since you’ll have to lift all the soil up to it…

18.   A bit of difference in the dampness of the soil makes a big difference to how well it will sieve.  Damp soil is noticeably heavier, so it’s harder work for you and the motor.  It also sticks together, so you get more lumps of soil going all the way through. If you've got a big pile to sieve, do a bit off the top, then stop for a cuppa/afternoon nap while the next bit dries out.

19.   If you don't have a friend, think about sticking a couple of big wheels on the feet on one end of the device, to make it easier to move around. It's not easy to move it alone.

20.   Stick a bit of board over the frame at the loading end, and cut out a circle to expose the open end of the drum.  When you misdirect a shovel full of soil, it bounces off the board instead of polluting your nice sieved soil in the wheelbarrow.  I used a bit of ancient plywood, but I reckon even corrugated cardboard would work (until it got wet).  This board also has the advantage that it keeps you away from the potentially sharp rotating edges on the end of the drum.

21.   A slope of 4" vertically over 48" horizontally seems about right.  It could go slightly steeper






Title: Re: machining down a nylon / polypropylene wheel
Post by: Nickel2 on April 30, 2018, 10:19:31 AM
I know it's been a while since this discussion, but I chanced upon an alternative way of making a trommel that would suit the handyman/gardener. If you own a small concrete mixer and can get a spare drum from a knackered one, this may be just the job for a spring project:

http://www.instructables.com/id/Soil-Sieve-Sifter-Machine/?utm_source=newsletter&utm_medium=email

N2


Title: Re: machining down a nylon / polypropylene wheel
Post by: knighty on April 30, 2018, 11:17:15 AM
acresswell I missed your post before... do you have any photos for us?


Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on April 30, 2018, 11:13:55 PM
acresswell I missed your post before... do you have any photos for us?

Not right now... it’s dark!

Will try to do some next time I’m outside in daylight...




Title: Re: machining down a nylon / polypropylene wheel
Post by: acresswell on September 07, 2018, 10:33:12 PM
Took these photos a couple of days after the above post but forgot to show you my collection of bodges!

(https://s15.postimg.cc/q83ryef5j/0_E11415_E-020_B-406_C-_B516-40_A0_B18_FB005.jpg) (https://postimg.cc/image/q83ryef5j/)

(https://s15.postimg.cc/730ionnmv/27_DF9214-78_F4-4_CFE-_A44_A-_A2_F8222_E732_B.jpg) (https://postimg.cc/image/730ionnmv/)

(https://s15.postimg.cc/gasr5d2ev/3246_CC04-_D7_DC-40_A2-_A663-437_A43_ECE74_B.jpg) (https://postimg.cc/image/gasr5d2ev/)

(https://s15.postimg.cc/8i23ddh07/608_F3_EB9-_F2_CC-40_CB-91_E3-53_DBD5_A43404.jpg) (https://postimg.cc/image/8i23ddh07/)

(https://s15.postimg.cc/z34m8xbnr/9_AD3_DE09-1_DC4-48_D2-8129-717_F58_DD8_C8_D.jpg) (https://postimg.cc/image/z34m8xbnr/)

(https://s15.postimg.cc/xo31k4xp3/CEC575_BA-3_D02-44_D1-9_BDD-2006_A77_BE47_C.jpg) (https://postimg.cc/image/xo31k4xp3/)

(https://s15.postimg.cc/gasr5bztz/EDF1659_D-1_F17-4424-_B1_AB-7_FC42_A2_F39_DB.jpg) (https://postimg.cc/image/gasr5bztz/)