Replacing Presto K10 rubber tire

[rsimms3]

Has anyone replaced the tire on their K8 or K10? If so, where did you secure the belt/tire? I had thought mine was okay flipping it inside out but there is too much vibration from a bad spot where it was packed with the tone arm rest mashed against the tire and a flat spot on the inside so turning it inside out isn't an option. I was thinking back to the sale of a 6N with a belt drive system and have sent an email to that user for details. I've looked around the net and can't find anything close to the Presto tire and wanted to check here before building a belt system or contact a custom rubber shop.

[markrob]

Hi,

Check out this guy:

http://www.terrysrubberrollers.com/

I have not used him personally, but from all accounts, he does great work.

Mark

[rsimms3]

Thanks! I've seen him referenced before related to the 6n rollers, but from his website it looks like he only does small rubber jobs less than 6". I also didn't realize he's here in Michigan as well. I may give him a call this week and talk shop. I was also looking at buying some square o-ring cord stock and splicing my own tire. I need to do the math to see just how close I can get in terms of speed with standard size o-ring stock.

[markrob]

Hi,

If the roller is a true idler, the diameter has no impact on the speed. If its a compound idler (two diameters on the same roller), then this is not true. In fact, if you can find a machinist with a tool post grinder, you may be able to true up the exisiting rubber surface of your idler. The determining factor would be if there is enough meat left after grinding such that the idler still functions properly.

Mark

[rsimms3]

That isn't the case here. The K10 is a rim drive system where the rubber tire is on the outside of the platter so the size of the tire determines the speed when driven by the motor. The motor is a fixed 1600rpm with a metal capstain that slides over to connect with the tire. The platter already runs a tad bit fast, I think from the rubber tire drying/shrinking over the years but could be intentional to over compensate for potential slipping during cutting. I'm leaning toward a belt system using a 24v DC scooter motor to drive the table and adjust the speed with a PWM that I already from another project.

[markrob]

Hi,

That is the mode in which the diameter of the tire has no effect on the speed. If you do the math, you will see this is true.

The ratio of the platter diameter to the capstan diameter sets the platter speed.

Let's take a simple example:

Assume the capstan is 1" in diameter, the idler is 2" and the platter 3".

The idler will spin slower than the capstan in the ratio of 1:2.

The platter will spin slower than the idler in the ratio 2:3.

The ratio of the capstan to platter will be the combination of the two ratio 1/2 x 2/3 or 1:3. Notice that the idler diameter is canceled out. The overall ratio is just the ratio of the capstan to the platter diameters.

A compound idler as is found on the old RCA 45 RPM players (e.g. 45-EY-3). The motor drives the lower diameter tire of the idler and the top diameter drives the rim. In this type of arrangement, the ratio of the top and bottom diameters is directly related to the platter speed. That's one of the reasons these players are not so hot at speed accuracy.

Hope this makes some sense.

Mark

[markrob]

That isn't the case here. The K10 is a rim drive system where the rubber tire is on the outside of the platter so the size of the tire determines the speed when driven by the motor. The motor is a fixed 1600rpm with a metal capstain that slides over to connect with the tire. The platter already runs a tad bit fast, I think from the rubber tire drying/shrinking over the years but could be intentional to over compensate for potential slipping during cutting. I'm leaning toward a belt system using a 24v DC scooter motor to drive the table and adjust the speed with a PWM that I already from another project.

If you go the DC motor/PWM route, you should add some sort of tach feedback. Unless the DC motor is very oversized, you will run into speed regulation problems open loop. A PM DC motor has a linear torque/speed curve, so its speed will vary as the load changes. A large platter flywheel effect will help keep the speed regulated, but you will constantly be messing with the PWM to keep things under control. A simple PI loop will make your life much simpler.

Mark

[rsimms3]

There is no idler involved in this situation, only the capstain on the shaft of the motor and the rubber tire on the outside of the platter. Should I not be calling the "sleeve" on the shaft of the motor the capstain?

Example:
2" capstain (motor) at 1600rpm, 36" platter = 88.88rpm
2" capstain (motor) at 1600rpm, 35" platter = 91.42rpm

That means that if I reduce the size of the tire, the rpm will increase.

[rsimms3]

That isn't the case here. The K10 is a rim drive system where the rubber tire is on the outside of the platter so the size of the tire determines the speed when driven by the motor. The motor is a fixed 1600rpm with a metal capstain that slides over to connect with the tire. The platter already runs a tad bit fast, I think from the rubber tire drying/shrinking over the years but could be intentional to over compensate for potential slipping during cutting. I'm leaning toward a belt system using a 24v DC scooter motor to drive the table and adjust the speed with a PWM that I already from another project.

If you go the DC motor/PWM route, you should add some sort of tach feedback. Unless the DC motor is very oversized, you will run into speed regulation problems open loop. A PM DC motor has a linear torque/speed curve, so its speed will vary as the load changes. A large platter flywheel effect will help keep the speed regulated, but you will constantly be messing with the PWM to keep things under control. A simple PI loop will make your life much simpler.

Mark

I was using this thread as a guide and Flo did mention a feedback loop for his motor.

https://lathetrolls.com/viewtopic.php?f=1&t=2505&start=20

Not being very knowledgeable in the arena of motors and such, this is good information related to PM motors (which the scooter motor is) and regulation under load change. I was looking at at 24v 2300rpm motor 1/25hp at 100w to drive the belt for the platter. My other thought was using the original motor and calculating the possibility of removing the tire (which sits recessed from the outer edge of the platter) to use the correct thickness of belt at the correct distance from the platter to drive it at the correct speed. The inside diameter of the tire is approximately 36" and the outside 38".

[markrob]

Hi,

Thanks for posting the picture. I see no. No idler. You could have the tire trued up at a machine shop to get rid of the flat. If the motor is an AC induction motor, you could use an inverter with a variable frequency oscillator (VFO) to trim the speed. I recall somebody posted a link to a off the shelf device that would to this for turntables. If you are handy, you could modify a cheapy automotive 12Vdc to 120Vac inverter to do this (stick with true sine type rather than modified sine if you can). I also found a link to a DIY inverter that looks interesting:

http://www.instructables.com/id/Adaptable-24vDC220vAC-Pure-Sinewave-Inverter-1/

If you only vary the line frequency by a small amount to compensate for the diameter difference, you can get away with applying constant voltage to the motor. If you plan to vary over a larger range, you need to vary both line frequency and voltage to avoid overheating the motor (constant V/F). The PIC based inverter would be easy to make into a true V/F drive with some code changes.

Mark

[Jesus H Chrysler]

Are you sure its the tire causing the vibrations? I've had similar issues on my k-10 and it turned out to be a burr on the worm gear. My tire does have a couple of flat spots so I went down that path for a while before figuring out the real culprit.
I'm assuming your spindle and gears are well greased? The manual calls for petroleum jelly but I'm thinking I might step up to something a little heavier for mine as the bushing is showing some wear
then...
Easy way to check: disengage the motor completely and spin the platter by hand. listen very closely while it slows down for any unusual noise. do it with the arm disengaged first, then do it with it engaged. If you hear something try and figure out at what point in the rotation it occurs. It might take a few spins and it might only be audible at low rpms but if you can narrow it down to one part of the rotation then you might get a fix on whats causing it.

If it turns out it is the tire you may want to try some printers blanket fix. http://www.baypressservices.com/acatalog/Blanket-Fix-1.html?gclid=CK30xpuvjL4CFS8V7AodtzIAsg I havent tried this yet but I plan to next time I order some for the print shop.

[soeffingodly]

Hi Fellow Trolls,

Did anyone ever find a good replacement for a Presto K-8 or K-10 rubber that goes around the platter rim? I have noticed that mine has a recess in it which causes the motor to to move in and out quickly every revolution. As you can guess it is definitely adding some flair to my cuts. Ha. I didn't think of trying to turn it around so I will give that a try. But in the event that fails does anyone have any insight?

I remember seeing some post where a gentleman found something in the pool arena that may have fit but the post ended there with no update.

Here is a shot of the engine wobbling:

I think I also need to look into the motor mount dampening as well as I think they are pretty shot. But I know this tire is playing into some of the "hum" I am getting in my grooves.

Thank you in advance!!

-S

[piaptk]

Someone posted on here a few years ago that a certain pool pump belt fit just right. I can’t find it on the mobile version of the board, but if you find it, post a link to the thread here.

[soeffingodly]

Someone posted on here a few years ago that a certain pool pump belt fit just right. I can’t find it on the mobile version of the board, but if you find it, post a link to the thread here.

I think this is the post, I remember reading it months ago. Finally found it. I think.

http://www.lathetrolls.com/viewtopic.php?f=4&t=474&start=20

correction again. my first post was correct. It is the seal from a pentair Challenger that works. It must be the OEM part and not the Aladdin go-kit part though. pentair p/n 355329

Appears you need two, side by side for it to work...? Looks like I'll find out after I flip the rubber to see if that keeps the motor from bumping a bit each revolution.

[soeffingodly]

Someone posted on here a few years ago that a certain pool pump belt fit just right. I can’t find it on the mobile version of the board, but if you find it, post a link to the thread here.

I think this is the post, I remember reading it months ago. Finally found it. I think.

http://www.lathetrolls.com/viewtopic.php?f=4&t=474&start=20

correction again. my first post was correct. It is the seal from a pentair Challenger that works. It must be the OEM part and not the Aladdin go-kit part though. pentair p/n 355329

Appears you need two, side by side for it to work...? Looks like I'll find out after I flip the rubber to see if that keeps the motor from bumping a bit each revolution.

Seeing 2 different versions of the O-Ring. An older model and a "newer" O-Ring that is "square." I assume the square is the one I'd be aiming for. May hit a pool supply joint tonight and pick 2 of them up. Update to follow at some point soon...

[soeffingodly]

OK, didn't pick up the Pentair part. I did however flip the rubber inside out and the dip isn't causing much of an issue any more. Still getting some humming from the turntable platter/unit though.

When I am cutting I power off the K-8 and I am still getting the platter rumble on the record. Aside from that it has been cutting pretty dam well. Maybe it needs more lubrication? (appeared to be greased pretty well when I took the platter off) Or maybe new motor grommits? They seem OK on the underside (a bit on the harder side but not obnoxiously concrete-hard). The rubber on top seem like a replacement is due (where the 2 top nuts screw on where the motor meets the top of the unit)

May be some user error in there as well. =)

I think I may still grab the Pentair replacement and see how those fit anyway. If/when I do I will report back.

In the meantime, any OG's have any additional insight or tests, I am game! (I think I missed disconnecting the cutting head and seeing what I get...)

[piaptk]

Krisd gets to Tucson in a couple days and we will be making a trip to Ace Hardware. I’ll hold off shipping your iRiaa box and throw a couple motor grommets in the box...

[soeffingodly]

Krisd gets to Tucson in a couple days and we will be making a trip to Ace Hardware. I’ll hold off shipping your iRiaa box and throw a couple motor grommets in the box...

You, sir are a gentleman and a scholar. Much thanks in advance!

[soeffingodly]

So I got a pair of the pentair belts. I didn't cut anything but gave it some revolutions. The pair could work as a replacement but it's still not as big as the original belt. Sorry I didn't get a good shot of the platter illustrating the girth of the rubber.

Size difference - original on the right

MVIMG_20180913_182250.jpg

I had to turn them on their sides to get both to fit inside as well as get more rubber for the motor to touch.

MVIMG_20180913_181348.jpg

[soeffingodly]

The final picture is the ORIGINAL tire. I will try my best to get good comparison shots at some point.

Going to keep looking for a better fit that is only 1 piece.