Need input on a possible way to make a T5 belt pulley

[Wheazel]

Hi

I am trying some different solutions for gearing etc, and decided I wanted to try a 1 stage belt reduction aswell.
The purpose of this thread is to get input on wheter my idea will work or not, and maybe some suggestions if I am lucky.

So, the idea is to make a large pulley for the T5 beltdrive standard. Planning to use 16mm wide belt.
I have access to a smaller lasercutter that can cut most plastics and woods, but wont cut aluminum or other metals.
I an planning to cut the outer ring of the pulley as shown in the image below. If i cut 3 of these rings out of 6mm acrylic plastic
and remove the "ears with holes" on one. THen glue them together like: ring with ears --- rIng with no ears --- ring with ears.
Then use a 6mm aluminum plate to build a centre that attaches to the outer ring.
(Some spoke design for acceptable weight and strength)
Pulleywidth will be 18mm. (then I can add some guide-sides to that later)

What do you think? What about materials? Gotta use something that handles water ofcourse, lightweight, and not metal.
A rough calculation shows that the acrylic in the rings would be around 350grams for a pulleysize of 384mm//241teeth.
Add to that the aluminium centrepiece. Depending on material in the outer ring I should be able to get away with slightly less maybe.
(Acrylic is roughly 1,2g/cm3, and quite durable)

 

[bandaro]

i did a similar thing, but made 60t t5 pulley for mine. yet to thoroughly test it but is seems to fit nicely.

I used some acetal plastic, 6mm thick, and cut it with a laser. keep in mind that the laser does not cut perfectly vertical, the top of the sheet will cut more than the bottom so dont try the full pulley in the one piece, i found the 6mm to be thin enough though. I then bolted 3 pulleys together to give me the width needed, they lined up almost perfectly, slightly off because the melting was not perfectly even, but close enough.

there is a thread started recently about making cheap pulleys, using metal pulleys for the groove belts, lathing them down and then using an epoxy to put teeth into the pulley, i think that would be a better option for the size you are after, if you have access to a lathe. that way its all cast in one piece, except the teeth, but if you roughen the aluminium up first they should be sweet. cant remember the thread title, something about making cheap gears...

also, i could only get a lightweight belt of t5 and it snapped in the second reduction, so look around for a strong enough belt.

 

[sami-b]

I'm on the same idé. but why not alu? if its thin it want be that heavy.
i'm going to use the start ring(dont know the name in english) from a cargo truck flywheel. and see how it goes.
you can se som pics here http://endless-sphere.com/forums/viewtopic.php?f=28&t=26178

 

[Miles]

If you're going to all this trouble. Why T5?

See also: http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=26122

 

[Thud]

Acrylic-no

polycarbonate-yes

little more expensive but WAY more durable. (I have several #35 sprockets in polycarbonate)
I also agree with Miles. If your growing your own, you can get a pitch better suited to your needs.
good luck. T

 

[Wheazel]

Thanks for the input.
Reason I picked T5 was obviously the ability to get alot of teeth in there without going to huge pulleys.
What standard of belt would be preferable to go for?

 

[Miles]

If you want to stick with 5mm pitch, I would use HTD or Gates PowerGrip GT3 or equivalents.

How much torque will you have at the driver pulley?

 

[Wheazel]

I do not have an accurate number to give regardning the torque, but this pulley is intended for a 1stage reduction with outrunner in the ~900gram segment.
From other threads I am guessing powerlevels could reach 2-3kW bursts during acceleration, and I am sure a belt with approx 15mm width will hold that no problem.

The HTD seem to be a sweet belt, I might go that route instead of the T5. Just have to check what kind of belts I can get my hands on here in Sweden.



Is this the HTD geometry mentioned in the previous post?

 

[Miles]

Yes.

See the tables in the attached for an idea of power capacities.

 

[spinningmagnets]

Using a standard with smaller teeth can mean being able to have the same reduction with a much smaller large sprocket/pulley. An example is when using the #219 Kart chain/sprockets instead of bicycle chain. Many have tried this and found that having a minimum of 11-teeth (11T) provides a significant reduction in chain noise, and a #219 sprocket with 11T is noticeably smaller than a BMX 11T.

As to belts/pulleys, Matt has experimented with a variety of them. Having an idler wheel that causes the small pulley to have more of its circumference "wrapped" with the toothed-belt will help reduce belt slippage. However, Matt found that even then, he had to increase to diameter of the small pulley to have enough belt-tooth engagement to eliminate slippage at higher power levels.

The shorter each tooth is (on the type of belt you have chosen, compared to the known HTD) the shallower it will engage with each pulley groove, and the easier it will slip. I'm not saying your belt-type choice is bad, since you haven't stated how much power you will be applying.

If you do not have any slippage on the small pulley after applying your peak loads, the smaller teeth of your selected belt-type will have been verified to be a good option, because it will have allowed you to use pulley ratios with a high reduction, while still using a simpler and more affordable single stage. Best of luck with whatever you try...

 

[Wheazel]

I can get hold of htd belts all the way up to 7 meters, so I will go to that standard. Will redraw my cutting files tonight and try to run them tomorrow friday.
For starters I will go for the acrylic I have available nad if it turns out well I'll invest in some polycarbonate or similar.
Again thanks for all the input.

 

[Wheazel]

Did lasercut some stuff today, and it came out good.
I want a cutter at home, they are sweet.
I did the HTD 5m profile according to the advice above, seem to be a good one.

192 teeth

 

[etard]

Somebody REALLY needs to provide this service to the community here, I personally would buy a few myself.

I wonder if you could reduce drag even further by using a "skip tooth" pattern where at various intervals a set of five or 10 teeth engage the belt and then flat and so on. I might cause premature wear to the teeth on the belt though.

The hard part is fitting the sprocket to the disc brake flange with enough inset to clear the chainstay but not hit the tire. :x

It would be convenient to use the exitsting cooling holes on say a 8" disc brake to mount to then use spacers as needed to shift the sprocket in or out. You would have to use a rim brake then, but who needs brakes? :wink:

Great job man, my only suggestion would be to glue the 3 layers together with the ring on one side.

 

[Zoltar]

Hi All,

I am pretty new arround here.
Just in the process converting my Dutch citybike
into a backwheel drivene-bike with 24V .
Nothings special but fun to do.
Now finishing up the cablemess...hope it all works well.

Came here for some inspiration and found this belt drive section...
I did cut recently some gears in Aluminum for my 3D printer.
That was actually not so difficult.
I did cut these in 8mm Alu sheet only up to 2mm from the edge, creating a rim.
Adding two halves together and you get a complete gear or pully.

CAD...

CAM....

Here a small video:
http://www.zoltar-cnc.nl/media/forum/HTD5.mp4

So this can even be done professionally or on a hobby CNC-machine.

Best regards, Chris.

 

[Miles]

Thanks Chris! I like it!

I don't know whether you've seen this thread but it's good to cross-reference anyway, so:
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=26122

 

[Zoltar]

Youre Welcome!

Stacking of 2D parts is a idea too, but maybe harder to get right/straight

The advantage of two halves is that it can simply be combined on the hub,
You've got your rim giving extra support next to the belt,
and it could look good too on the side

Ive been exploring CNC-cutting aluminium on my hobby machine for some time.
With good Alu and a decent cutter its actually pretty easy.
So if you have a Fab-Lab in your neighberhood or some CNC-addict...
it should not be that hard to get a decent result.

Looking forward to your final solution!

Chris.

 

[etard]

Very Cool Zoltar! Can you post a pic of your CNC?

I wonder what happened to the OP"s belt pulley drive?

 

[Kin]

Just want to subscribe here in case people post some more useful links.

 

[Zoltar]

Hi Etard,

Just check the URL under the avatar....

OP?

 

[Miles]

OP?

"Original poster", I think.

 

[Zoltar]

"I wonder what happened to the OP"s belt pulley drive?"

Indeed OP, learned a new shortcut (SC)

I also do wonder how Wheazel's the Pully did work out.
Was its strong enough for this purpose ?
How the flanges on the gear where solved.
(an aluminium rim -bolted trough-on both sides would provide sufficient strength/body I guess)

Overhere Ive modified my HTD pulley a bit and also found that
even the belts have a slight variation in pitch.
Could be caused because its a (China) non brand.

Testing it wit a longer HTD belt proved to work fine.
Now that Ive received a short one wich I am actually gonna use...
the fit of the HTD 5 on the pulley is just a tiny bit to tight.
So slight tooth change and gonna have to cut another pair.

Greetings, Chris.

 

[Zoltar]

A member came up with this idea:

http://www.cnczone.com/forums/epoxy_granite/135197-make_your_own_timing_pulley.html

Casting a HTD-Gear from epoxy.....Idea??

-chris-

 

[Miles]

Hi Chris,

Interesting. Thanks for the link.

This is a similar method which seems to work well:
http://endless-sphere.com/forums/viewtopic.php?p=171685#p171685

 

[bobc]

My experience making a "stacked laminate" pulley - 1st, the tensile members in the belt are inside it, not on the surface, so the outside of the pulley needs to be a somewhat smaller diameter than the belt pitch and N-teeth might lead you to suppose - on the gates carbondrive belt i needed to subtract 1.8mm (!) from the calculated diameter. This might explain why the belt pitch seemed wrong on the pulley (?).
2nd - Zoltar - your CNC'd pulley made from 2 halves - why nottaper the hole in the middle and compress a tapered 'olive' onto the shaft by screwing the 2 halves towards each other. I've made a number of such "home-made taperlock" pulley fixings with 100% success (you could CNC the taper but I suspect you'd be better served popping it into the lathe). The tapered fixings are guaranteed central, no backlash, no damage to shaft, unlikely to come loose etc. etc. - I've stopped using grubscrews ;^)

 

[Zoltar]

Hey hello Miles,

Thats also a good suggestion!
Thanks for pointing this topic out.

A granite -epoxy pulley would be too heavy also - that is, on a bike....

"home-made taperlock".... This is a valid solution to go for Bob.
Ive tought about that option for a moment, then this is a quick way to test and cut these pulleys.

Grubscrews are indeed not very favorable but can do the job for some light duty tasks.

-chris-