Belt and pulley choice.

Hello all,

I have to buy a belt and a pulley for this project: Zaka Elab | Una paso más allá

I don't know if I did the right choice, so I let it here so you can help me to know wheather it's
right or not. My doubt is that I'm not sure if it's the correct match.

Here are my choices:

Belt:

0.08 Pitch, 1/4" Wide, Open Ended Neoprene Belt
Part Number
Unit
Pitch
Belt Width
Max. Length
Material
Tension Member
No.of Grooves/Foot

Pulley:

.080(MXL) Pitch, 16 Teeth, Polycarbonate Timing Pulley
Part Number
Unit
Pitch
No. Of Grooves
Material
Belt Width
Bore Size
Bore Configuration
Flange Configuration
Pitch Diameter
Outside Diameter
Overall Length

I appreciate your help.

Thanks.

Zaka.

Looks fine to me. What specifically is your concern?

HI Zaka,

You need a pulley at each end of your instrument.
So you need two pulleys.

The pulleys and belt need to have the same 'belt width'.
The pulleys and belt need to have the same 'pitch'.
I think this 0.25" belt width and MXL pitch are reasonable.
However this instrument looks like it may have XL pitch.


You might decide to switch to XL pitch.

The belt you mention (A 6Z16-C025) is 'open ended'.
That means it is not a loop.
You need a loop so that you can wrap it around the two pulleys.

I don't know how long your instrument is going to be.


That one looks like it is about 25 inches between the pulleys.
A belt like A 6Z16-648025 might work.
https://sdp-si.com/eStore/PartDetail.asp?Opener=Group&PartID=70331&GroupID=213
It is a loop of about 52" circumference.

You can get other sizes too.
Pick the size closest to what you want.

Then you can use this
http://www.sdp-si.com/Cd/default.htm
to calculate the distance between the encoder and the motor.

I put in...

0.080 pitch
36 grooves for both pulleys
25" desired center distance
I got out...
648 grooves in the belt and
24.48" center distance

You have not mentioned the motor or the encoder shafts.
The 'bore' on the motor's pulley must match the motor shaft diameter.
The 'bore' on the encoder's pulley must match the encoder shaft diameter.
Of course the motor will need to be strong enough to move your load fast enough to play the music you want to play.
That is a complex calculation.

You must decide how the pulleys will hold the shafts.
The pulley you mentioned has no set screw or pinning hole.
Do you have access to a machine shop?

The instrument in the picture seems to have pulleys that are about 1" in diameter.
This pulley (A 6T16-036DF2508) is about that diameter has a .25" bore in an "Aluminum "T"-Insert".
The T insert has a set screw in it for mounting to a flatted shaft.
If your motor and encoder have 1/4" flatted shafts this pulley might be good.

Set screws will work but work loose.
Pins are better.

That's a lot to think about.
Questions?

RonH

Hello RonH,

Thanks for your kind answers.

Here I let some comments about them.

I_ronh:
You need a pulley at each end of your instrument.
So you need two pulleys.

Yes, of course, I'm only concerned about the type of the pulley, so
I would buy two of them.

I_ronh:
However this instrument looks like it may have XL pitch.

I thought that it would lighten the system, so the motor would have
to move less weight.
What do you think?
Would the MXL resist all the movement required or better switch to XL.

I_ronh:
The belt you mention (A 6Z16-C025) is 'open ended'.
That means it is not a loop.
You need a loop so that you can wrap it around the two pulleys.

Actually, the one used in Lemur's GuitarBot is open ended, but it's
attached to the slider(you can zoom in the picture to note it). That's
a big advantage because I can buy one large open ended belt and
adjust it to my design and even make mistakes(as, obviously, gonna
be).

I_ronh:
You have not mentioned the motor or the encoder shafts.
The 'bore' on the motor's pulley must match the motor shaft diameter.
The 'bore' on the encoder's pulley must match the encoder shaft
diameter.
Of course the motor will need to be strong enough to move your
load fast enough to play the music you want to play.
That is a complex calculation.

The motor's bore are about 2~3 mm = 0.07~0.11 inches (I don't have
them with me right now to give you more precise data)
I've picked the smaller pulley's bore from the MXL series, 0.125 inches,
I'll have to do some adjustment.

The motors are recycled from a printer and I don't have enough knowledge
to predict if they're gonna work or not, so I'll be doing a lot of trial/error.
Is there a way to extend the motor shaft so it could be attached to a wider
pulley?

I_ronh:
The pulley you mentioned has no set screw or pinning hole.
[...]
This pulley (A 6T16-036DF2508) is about that diameter has a .25" bore in an
"Aluminum "T"-Insert". The T insert has a set screw in it for mounting to a
flatted shaft.

Does the T-Insert refer to the protrusion in the middle of the pulley with holes
for screws?
I thought about using set screws, but am not sure how, since my motor's shafts
aren't flatted.

I_ronh:
Do you have access to a machine shop?

Do you talk about the place where to make parts? Yes, I have one. What I would
have to go there for?

I_ronh:
Set screws will work but work loose.
Pins are better.

Could you tell me more about pins? How to buy or make them?
When and why use them?

Thanks for your awesome answer.

Best regards.

Zaka.

Hello Chagrin,

Chagrin:
Looks fine to me. What specifically is your concern?

My concern is that I don't know if my choice will fit with my needs, so I ask for
guidance to wiser guys.

Thanks.

Zaka.

Hi Zaka,

I need to be quick.
I’ll come back to belt and pulley things.

The motor and drive are the heart of this.
We could do the actual physics F=ma.

But, did you see this motor working in the printer?
How heavy is the load it moved in the printer compared to your slider?
How fast did the load move in the printer?

If you are convinced the motor is ok, you need a drive for it.
Will that come from the printer too?
If it will, do you know how to command the drive?
If you need a new drive, what will it be?

String tension is a factor.
It will tend to bend the instrument.
It will load the motor with friction too.

If the slider is heavier than the ink cartridges the motor moved in the printer…
… or if friction is going to be more…
… then you’ll save time and money getting a bigger motor/drive first.

I assume this motor was moving the ink jet assembly in the printer.
Was the belt tension pulling directly on the motor shaft in the printer?
Or was the pulley supported by other bearings?

My old printer seems to have a dc motor shifting the ink.
I don’t think it accelerated very fast.
Maybe we can find a video of an ink jet printer working and compare movements to the instrument…?

Best,
Ron

I would stick with MXL. The smaller pitch is a better fit for smaller pulleys (which will give you more torque) and the belt itself is plenty strong, probably on the order of 50lbs of tensile strength and way more than the torque your motor will produce.

You do need some way of securing your pulley to the motor shaft and I do think a set screw is the best way. I've never had a set screw work loose on anything I've ever built. If your shaft doesn't have a flat on it it's just a matter of grabbing a file and making one. You could drill and tap right through the side of the pulley but a metal "T" hub (looks like a T from the side) would be preferred.

store.makerslide.com has good prices on MXL belt and pulleys, but the pulleys all have .25" or 5mm hubs. pololu.com has a nice selection of gearhead motors with encoders attached if you want to go that route.