Panos,
I read your message before I saw your photo.
I was thinking that you had devised a crafty way to intersect the motor pulley with an idle pulley, to absorb as much motor noise as possible - before the belt reaches the platter rim.
But no! It seems that the motor pulley is closely actively driving the rim and the idle pulley simply increases rim surface belt contact area. Interesting.
Have you got a silicone belt?
That should help absorb vibrations for the motor reaching the platter... It's what I run on our LP12.
I read your message before I saw your photo.
I was thinking that you had devised a crafty way to intersect the motor pulley with an idle pulley, to absorb as much motor noise as possible - before the belt reaches the platter rim.
But no! It seems that the motor pulley is closely actively driving the rim and the idle pulley simply increases rim surface belt contact area. Interesting.
Have you got a silicone belt?
That should help absorb vibrations for the motor reaching the platter... It's what I run on our LP12.
Sondeknz, I do not have a silicone belt. As a matter of fact, I intend to use a 'no-stretch' belt, namely polyester thread (sulky 0.004mm) and cassette tape (actually mini dv tape). As you've said, it's not a concept I've come up with. The photo I've attached in the previous post is from Artemis Labs SA-1 turntable. But the concept of a belt tensioner is very common in numerous applications. I wonder why it is not common in turntables. My objective is to maximize contact area between belt and pulley. It's less about reducing vibrations.
Panos, thanks for clarifying this thinking.
"It's less about reducing vibrations."
I don't want to just nod like a sycophant, when I feel that we are assembled here as something of a knowledge pool, to draw upon each other's experiences and know-how and hopefully help each other achieve better outcomes.
On that basis, NIFFY very respectfully showed me tonight that my PTFE motor pulley idea could easily be bettered - and POM is a far better material to use for a pulley, than PTFE. I came out ahead.
[Thanks, Niffy.]
In the interests of helping you to get the very best outcome from all your hard work on this project, I need to say: I'm really surprised that your focus is on increasing platter rim belt contact area.
The outer platter already provides the belt with so much more turning leverage, compared to conventionally driving the same platter from the smaller diameter sub-platter. It doesn't need any more help.
For a helpful example, think how much more turning power a long-handled wrench has, compared to a very short-handled wrench grasping the same seized bolt. It is the same when attempting to turn a 12" platter from the outer edge. The greater distance from the spindle provides dramatic increases in leverage. Quite simply, it's MUCH easier to turn.
Furthermore, the more belt contact you have with the platter rim, the more faithfully motor vibrations and noise will be transferred through to your platter - and your stylus.
So, I've got to ask: Why the big focus on an increase in belt contact here? Is there a problem you are you trying to solve? What is it?
I'm happy to be proven wrong, but surely your efforts would be much better invested in getting unavoidable motor vibrations away from the platter that you are trying to drive from the rim?
If you reconfigured to mount the motor pulley further away from the platter rim, your idler could still be put to very good use here, by providing a vibration "sink point" closer to the platter - before the vibration-loaded belt reaches the platter.
Having your motor further away from the platter is also another win!
Under this reconfiguration, normal motor vibrations would leave the motor pulley via the belt - and then much of that vibration would be transferred to the "sink point" idler pulley.
A much smoother belt would then reach the platter to drive it, without as much distortion inducing noise and vibration.
This motor vibration minimisation issue - very similar to understanding how best to mount the motor to the Linn top-plate - is absolutely critical in getting best sound from (even) the highest spec LP12.
I do hope you don't mind me saying... It is your project, after all.
Give it some thought, and feel free to push-back hard, if I've missed something important here. 😉
"It's less about reducing vibrations."
I don't want to just nod like a sycophant, when I feel that we are assembled here as something of a knowledge pool, to draw upon each other's experiences and know-how and hopefully help each other achieve better outcomes.
On that basis, NIFFY very respectfully showed me tonight that my PTFE motor pulley idea could easily be bettered - and POM is a far better material to use for a pulley, than PTFE. I came out ahead.
[Thanks, Niffy.]
In the interests of helping you to get the very best outcome from all your hard work on this project, I need to say: I'm really surprised that your focus is on increasing platter rim belt contact area.
The outer platter already provides the belt with so much more turning leverage, compared to conventionally driving the same platter from the smaller diameter sub-platter. It doesn't need any more help.
For a helpful example, think how much more turning power a long-handled wrench has, compared to a very short-handled wrench grasping the same seized bolt. It is the same when attempting to turn a 12" platter from the outer edge. The greater distance from the spindle provides dramatic increases in leverage. Quite simply, it's MUCH easier to turn.
Furthermore, the more belt contact you have with the platter rim, the more faithfully motor vibrations and noise will be transferred through to your platter - and your stylus.
So, I've got to ask: Why the big focus on an increase in belt contact here? Is there a problem you are you trying to solve? What is it?
I'm happy to be proven wrong, but surely your efforts would be much better invested in getting unavoidable motor vibrations away from the platter that you are trying to drive from the rim?
If you reconfigured to mount the motor pulley further away from the platter rim, your idler could still be put to very good use here, by providing a vibration "sink point" closer to the platter - before the vibration-loaded belt reaches the platter.
Having your motor further away from the platter is also another win!
Under this reconfiguration, normal motor vibrations would leave the motor pulley via the belt - and then much of that vibration would be transferred to the "sink point" idler pulley.
A much smoother belt would then reach the platter to drive it, without as much distortion inducing noise and vibration.
This motor vibration minimisation issue - very similar to understanding how best to mount the motor to the Linn top-plate - is absolutely critical in getting best sound from (even) the highest spec LP12.
I do hope you don't mind me saying... It is your project, after all.
Give it some thought, and feel free to push-back hard, if I've missed something important here. 😉
When press fitting the pulley or idler wheel onto the Maxon motor be very careful not to exceed 80N of force. Doing so will destroy the bearings.
When press fitting the pulley on my motor I used my pillar drill as a press. I fitted an M10 bolt, which I had faced, into the chuck to act as a flat plunger. I placed my kitchen scales on the bed so that I could monitor the force applied.
I found a scrap of 3mm bar that luckily had exactly the same diameter as the motor, 3.05mm. I test fitted the pulleys to this so I could make sure that I did not use excessive force.
I also made a pulley puller so that I could remove the pulley or adjust it's position without putting any force through the bearing.
Niffy
When press fitting the pulley on my motor I used my pillar drill as a press. I fitted an M10 bolt, which I had faced, into the chuck to act as a flat plunger. I placed my kitchen scales on the bed so that I could monitor the force applied.
I found a scrap of 3mm bar that luckily had exactly the same diameter as the motor, 3.05mm. I test fitted the pulleys to this so I could make sure that I did not use excessive force.
I also made a pulley puller so that I could remove the pulley or adjust it's position without putting any force through the bearing.
Niffy
I would agree with all of your points except about having the motor further from the platter.
Low-stretch belts sound better than stretchy belts.
If you move the motor further from the platter the length of free belt increases. The stretchiness of the belts material is proportional to its length, double the length double the stretchiness.
This is one of the reasons I have gone for very short belts.
Niffy
Good point, making mention of the rules changing, when belt material changes.
I have to confess that I have very little experience with non-stretchy belts - but it seems that a lot of the initiatives on this deck are attempts to accommodate the unconventional non-stretchy belt - at the cost of some pretty critical vibration controls.
Trouble is, regardless of where the motor pulley is mounted, the "thread" belt length is being extended by the addition of an idler pulley - requiring a degree of "double-back - introducing extra belt length that increases the undesirable stretch opportunity that you have identified.
So, to summarise: any non-stretchy belt advantages are being lost because of the need to dramatically extend the belt's length t accommodate the idler pulley. Meanwhile other critical vibration controls are being sacrificed for what would seem... very little gain.
I have to confess that I have very little experience with non-stretchy belts - but it seems that a lot of the initiatives on this deck are attempts to accommodate the unconventional non-stretchy belt - at the cost of some pretty critical vibration controls.
Trouble is, regardless of where the motor pulley is mounted, the "thread" belt length is being extended by the addition of an idler pulley - requiring a degree of "double-back - introducing extra belt length that increases the undesirable stretch opportunity that you have identified.
So, to summarise: any non-stretchy belt advantages are being lost because of the need to dramatically extend the belt's length t accommodate the idler pulley. Meanwhile other critical vibration controls are being sacrificed for what would seem... very little gain.
Hi, This how I arage the drive around my rim. The motor pod is self weighted as I have put measured amount of lead shot at the rear is two small containers. By adding more lead, you obviously add more tension to the Mylar belt. The pod only sits on the front 2 spiked, a 3rd none spiked foot is there at the rear, but does not touch the platform, just there to stop the unit falling over if the belt gives way. The Mylar belt lasts about a year.
Cheers
Cheers
Attachments
Sondeknz, gentlemen,
thanks for the feedback. I am not claiming that my views are correct. I am just sharing my ideas. And I take all feedback with good intentions, so not worries at all that I might be offended. After all, we are all here to become wiser and not to show off (at least, much more about the former than the latter -)).
With respect to belt-drive, the usual challenges I read in forums are the following:
a. stretching
b. slippage
c. resonance at the non-tensioned part of the belt
So, my quick reaction to those challenges would be the following:
a. use a non-stretch belt material, such as mylar tape or cassette tape. The caveat: does the material provide enough friction?
b. slippage usually occurs at the pulley of least contact, i.e. the motor pulley. Solution? Increase the contact area at the motor pulley, hence my suggestion of the tensioner belt. Caveat: there may be more vibration transferred from the motor to the platter and then to the stylus.
c. resonance can be tackled with the tensioner wheel
So, that's why I intend to test the Artemis Labs approach with the idler pulley used as tensioner for the belt. And I am going to use a 6.3mm cassette tape for my experiment.
In case I am putting wrong priorities in my line of thinking, please let me know.
P.S. I've tried the rim drive approach. If I put higher pressure on the motor shaft, the motor tends to slow down. Probably, the OL controller is not configured to overcome extra torque resistance.
P.S.2 I will try the same with the Maxon motor I am expecting..., i.e. both rim-drive and belt-drive.
DNic,
thanks for the input. How thick is your Mylar belt? Looks like 4-5mm?
Where di you get it from? On the internet, the majority of mylar belts I find are self-adhesive. I would prefer non-adhesive of course.
For the moment I am planning to use cassette tape (I guess we all remember what cassette tape looks like -)). I have also ordered polyester thread that I am going to use in place of the belt.
Cheers,
P.
Hey Panos,
Thanks for the nice response.
It's good to read that we are all on the same page about being students of learning here - and we're not having to tip-toe around each other's egos. Appreciated.
When I was a very young man, the unquestioned market dominance of the LINN SONDEK LP12 was being very seriously challenged by a newcomer with a strange name. By many reliable accounts, the LP12 was falling behind the young upstart.
The ROKSAN XERXES is an absolute legend! A widely acknowledged LP12 beater and that is no faint praise. I'd love to own one, myself.
I know the original deck has aging issues - with a saggy gut and in need of a heart transplant - but it seems like you have the necessary skill and equipment to replicate and even vastly improve upon these failing components, with relative ease.
If it were me, I would probably be sticking with the original configuration and focus on replicating - or indeed improving upon - the many recommended upgrades that the XERXES has undergone over the years; without trying to completely rethink the winning recipe.
But that's just me.
I guess you need to work through your XERXES reconfiguration ideas, in an attempt to beat Touraj Moghaddam at his own game - a real challenge, to be sure.
Having expressed reconfiguration design concerns in my previous post - and my emphatic recommendation NOT to ignore vibration management - I acknowledge my lack of experience with non-stretch belts. So, at this juncture I think it best for me to just sit back and watch how your project comes together.
Who knows? You may hit a home run!
I certainly hope so... 😊
Yes, indeed we are on the same page, Sondeknz.
being in the comfortable position of having a newly restored Lenco L78 (idler-drive tt), I can experiment with my trusted Xerxes without any stress or pressure. What I was studying in the UK (1989), I used to arrange several auditions at hi-fi stores on Saturdays. For my ears, Roksan was a clear winner (over the LP12) with respect to rock music, that used to be my favorite at the time (and still live today). More vibrant, more lively. But the original power supply was problematic. Hence, I changed to the Origin Live kit sometime in around 2000.
In an honestly, the Xerxes is much simpler than the LP12.
Now, with the knowledge of a gray-haired person, I am confident that the original Xerxes (designed at a price point) design can be fine-tuned. That's why i am playing around with various concepts. I am not adamant on any of them, and that's why I think I can be quite objective. I'll try as many concepts as I can, and i will report back with my findings.
I am not suggesting that I can better Touraj's initial concept, but I do not have any restrictions whatsoever, as I so not intent to create a commercial product.
I am testing and reporting what I find. All and any feedback is welcome, of course.
Cheers,
Panos.
being in the comfortable position of having a newly restored Lenco L78 (idler-drive tt), I can experiment with my trusted Xerxes without any stress or pressure. What I was studying in the UK (1989), I used to arrange several auditions at hi-fi stores on Saturdays. For my ears, Roksan was a clear winner (over the LP12) with respect to rock music, that used to be my favorite at the time (and still live today). More vibrant, more lively. But the original power supply was problematic. Hence, I changed to the Origin Live kit sometime in around 2000.
In an honestly, the Xerxes is much simpler than the LP12.
Now, with the knowledge of a gray-haired person, I am confident that the original Xerxes (designed at a price point) design can be fine-tuned. That's why i am playing around with various concepts. I am not adamant on any of them, and that's why I think I can be quite objective. I'll try as many concepts as I can, and i will report back with my findings.
I am not suggesting that I can better Touraj's initial concept, but I do not have any restrictions whatsoever, as I so not intent to create a commercial product.
I am testing and reporting what I find. All and any feedback is welcome, of course.
Cheers,
Panos.
...And you've got a fully restored LENCO L78 as a reference point. Nice.
Be careful not to put the new MAXON pulley under too much lateral load. I have read that the MAXON motors don't last long in a high-tension environment.
Given that they are a costly little ticker, it's something to keep in mind.
Be careful not to put the new MAXON pulley under too much lateral load. I have read that the MAXON motors don't last long in a high-tension environment.
Given that they are a costly little ticker, it's something to keep in mind.
You are absolutely right, Sondeknz.
I will be careful with the Maxon motor indeed. But think about it, (I hope it's not due to ignorance), and admitting that synergy is key, I am still willing to put together some interesting principles, to build a 'prototype' tt. For example, high inertia platter, heavy duty/low friction bearing, low vibration/high torque motor and appropriate drive principle. Heavy plinth is always a plus.
I am not claiming that the Xerxes has all of that, but it definitely has some.
In a couple of weeks I should be receiving the maxon motor (and also the Alfred Bokrand tonearm for my Lenco). Some interesting head-to-head comparisons will take place.
P.
I will be careful with the Maxon motor indeed. But think about it, (I hope it's not due to ignorance), and admitting that synergy is key, I am still willing to put together some interesting principles, to build a 'prototype' tt. For example, high inertia platter, heavy duty/low friction bearing, low vibration/high torque motor and appropriate drive principle. Heavy plinth is always a plus.
I am not claiming that the Xerxes has all of that, but it definitely has some.
In a couple of weeks I should be receiving the maxon motor (and also the Alfred Bokrand tonearm for my Lenco). Some interesting head-to-head comparisons will take place.
P.
(Where di you get it from? On the internet, the majority of mylar belts I find are self-adhesive. I would prefer non-adhesive of course.)
Yes you are correct, it is 55mm wide, the Mylar tape that I use has adhesive on one side, which obviously becomes the outer side. I used it at 1st as a trial, but was so thrilled with the results & simplicity of making a belt. That I just stayed using it, the glue does eventually wear down & becomes much less stick & has never caused any problems. The only think I would look for the next time I need to purchase a roll is to get it coloured as I think it would make the alignment of the tape easier.
Galiber T/T actually sell a ready made belt that they use for their own T/T's. Last time I inquired it was about $30 for the belt, but for me $50 freight!!. Which I was not prepared to pay & the owner was not prepared (middle of Covid) to go to the post office.
Cheers
Yes you are correct, it is 55mm wide, the Mylar tape that I use has adhesive on one side, which obviously becomes the outer side. I used it at 1st as a trial, but was so thrilled with the results & simplicity of making a belt. That I just stayed using it, the glue does eventually wear down & becomes much less stick & has never caused any problems. The only think I would look for the next time I need to purchase a roll is to get it coloured as I think it would make the alignment of the tape easier.
Galiber T/T actually sell a ready made belt that they use for their own T/T's. Last time I inquired it was about $30 for the belt, but for me $50 freight!!. Which I was not prepared to pay & the owner was not prepared (middle of Covid) to go to the post office.
Cheers
Nice.
The Maxon data sheet for the Re-Max 29 with sintered bearings recommends a maximum radial load of 5.5N, 5mm from the flange. With most turntable designs the the load, where the belt runs, will be quite a lot more than 5mm from the flange. In my case it is about 12.5mm. I think a good general rule of thumb would be to treat this as a torque,
5.5N x 5mm = 27.5mNm
For safety and longevity of service I would aim for no more than half of this. I have made my belts so that belt tension is 0.7N. My belt makes a 90° angle at the pulley. This results in a radial force of 1N. This would give a "torque" of 12.5mNm, within my safety margin.
Whether belt slip is going to be an issue or not will be dependent on several factors.
The coefficient of friction between the pulley and belt. For instance, Aluminum will have a higher CoF than Delrin.
The friction of the main bearing. If the bearing has high friction the belt will be more likely to slip.
Belt tension. If you have higher belt tension it will result in greater pressure between the belt and pulley reducing the liklihood of slipping.
Platter mass or more accurately moment of inertia. A heavier platter is more likely to suffer belt slip as it is accelerated up to speed than a light on. Once up to speed the mass of the platter shouldn't make a difference (assuming that the additional mass doesn't increase bearing friction). I always spin my platter up to speed manually to prevent belt wear and stretch.
Once you get to the point where the belt isn't slipping increasing belt tension of the CoF further won't have any benefits, it might actually be harmful by increasing noise.
Niffy
OK, DNic, I have been convinced and ordered a 5mm mylar tape. I will try to make a Mylar belt and revert with comments. I wonder how it will compare with my current belt (from Origin Live), which is rubber with limited (but not zero) stretch.
Cheers,
Panos
Great info, Nuffy.
I too have always push-started my platter.
I believe it explains why nearly 20-years later, the OL DC-100 motor is as sweet as a nut.
Best practice, IMHO.
I too have always push-started my platter.
I believe it explains why nearly 20-years later, the OL DC-100 motor is as sweet as a nut.
Best practice, IMHO.
I agree with your analysis, Niffy.
I am not worried about the startup behavior, because as you've said, the platter can be turned by hand to help the motor to reach the appropriate speed. The question is what happens if there is a sudden drag increase, while the cartridge is tracking the record. Then the following things may happen:
a) the belt slips
b) the belt stretches
c) the motor decelerates
I think that belt slippage can be avoided with a high friction coefficient of the belt and/or high tension too. Similarly, belt stretching can be avoided by using a non-stretch material, such as polyester, mylar, etc. But in my opinion -and correct me if I am wrong- the real challenge is to avoid motor deceleration. Until that moment, the motor may be running at low or very low torque. So, how can it sense that there is an instant increased torque requirement? Even if the controller is sensitive enough (e.g. negative resistance principle), I am not sure whether it can react quickly enough. So, given that context, I guess that the only way to avoid deceleration is to have high rotational inertia of the platter, so that the motor will not have to counteract the increased stylus drag, because the rotational momentum will be high enough to be audibly reduced.
So, if my train of thought is correct, belt friction coefficient and stretch behavior should practically be irrelevant, if the platter has sufficiently high rotational inertia. This does not necessarily mean high platter mass. It means high mass at the platter rim, to achieve a flywheel effect.
My two cents... Thanks.
Panos
Hi Panos,
You asked,
What would cause this sudden drag increase?
The drag applied by the stylus in the groove is very small. The variation from unmodulated to full level modulation would be not be sufficient to cause belt slip unless the belt was right on the cusp of slipping anyway. It may cause a very very slight slowing of the platter. Higher belt tension will not address this. A lower stretch belt might be beneficial. Higher platter inertia will help as may higher motor torque.
If your bearing shows sudden changes in drag enough to cause belt slipping or speed fluctuations then you have a faulty bearing.
Any other external factors such as a foreign object coming into contact with the platter could not be considered normal operation.
If you have a sudden decrease in the friction between the belt and the pulley then you need to clean the belt and pulley or replace the belt.
You asked,
What would cause this sudden drag increase?
The drag applied by the stylus in the groove is very small. The variation from unmodulated to full level modulation would be not be sufficient to cause belt slip unless the belt was right on the cusp of slipping anyway. It may cause a very very slight slowing of the platter. Higher belt tension will not address this. A lower stretch belt might be beneficial. Higher platter inertia will help as may higher motor torque.
If your bearing shows sudden changes in drag enough to cause belt slipping or speed fluctuations then you have a faulty bearing.
Any other external factors such as a foreign object coming into contact with the platter could not be considered normal operation.
If you have a sudden decrease in the friction between the belt and the pulley then you need to clean the belt and pulley or replace the belt.
Thanks for the feedback, Niffy.
I agree with what you are saying.
As a matter of fact, I am approaching the issue from a theoretical perspective. I do not have an issue with my bearing, which works flawlessly. However, while measuring the speed of the platter, I see when I lower the needle on the record, the speed is measurably reduced. So, stylus drag is significant at least with my Xerxes platter (I have not tested the same with my heavier Lenco platter). In my opinion, to remain as unaffected by stylus drag as possible, the only option is to have a platter with as high rotational inertia as possible. In simple terms I could say 'heavy platter' or 'high mass platter', although to be precise it's technically not the same thing.
I agree with what you are saying.
As a matter of fact, I am approaching the issue from a theoretical perspective. I do not have an issue with my bearing, which works flawlessly. However, while measuring the speed of the platter, I see when I lower the needle on the record, the speed is measurably reduced. So, stylus drag is significant at least with my Xerxes platter (I have not tested the same with my heavier Lenco platter). In my opinion, to remain as unaffected by stylus drag as possible, the only option is to have a platter with as high rotational inertia as possible. In simple terms I could say 'heavy platter' or 'high mass platter', although to be precise it's technically not the same thing.