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In Reply to: My beautiful looking, but lousy sounding new Empire 398 (pics) posted by albertoderoma on December 16, 2006 at 17:16:25:
Empire had a very peculiar way of modifying their turntables for 50Hz service. The pulley was not user-replacable, so instead they opted to offer (Get this),
a different platter with a slightly larger diameter rim for the belt!!! Insane, eh?I'm guessing that your turntable has the 50HZ-spec platter which would actually run fast since the motor is running faster (60hz).
Measure the diameter of the inner platter rim where the belt rides and post it. I'm sure that someone here has a standard Empire platter to measure and compare the results.
Check it out!
Cheers,
Close to the Edge, down by the river....
-Ray
Follow Ups:
So the height at which the belt rides is going to determine the final speed produced by the assembly.I wonder if your motor had been tightened down incorrectly? My motor floats with a spring supplying tension on one of the three legs. You simply loosen or tighten the motor screws to adjust the height of the belt, or you can select a different ball bearing for the bearing well (on the ROK...I am not sure what the bearing configuration is on your 398).
Then the screw with the spring is adjustable for the tilt which will fine tune the speed.
Is your platter convex?
If so we need you to adjust the motor screws so the motor is level and the belt is riding at the crest of the convex points. Check your speed.
Now adjust the motor screws to align the belt either higher or lower than the crest which should slow you down to a sensable speed. Then adjust the tilt of the motor to achieve fine speed adjustment.
It really might be just this simple if that platter of yours is convex.
My Empires came with two pulleys, one for 50HZ
and one for 60Hz. I have never heard of the platter thing but it is possible I guess.
When I worked for Musicraft I remember changing a pulley on a Empire for a customer that had moved to the US and wanted it to run on 60 hz. I don't remember which model it was though. So at least some of the Empires had separate 50 and 60 hz pulleys.Dave
That certainly is the logical approach. The whole platter and bearing exchange thing they did early on was just plain bizarre!
Close to the Edge, down by the river....
-Ray
having owned both 50Hz ( Export model ) and 60Hz 208 Empires,( and 598/698 Empires ) the difference was in the Papst motors alone; spindles, platters and belts were otherwise identical
"Insane Eh?"
*Quite*Grins
.
Close to the Edge, down by the river....
-Ray
and these don't readilly interchange between these Empire models.
The 598's had a subplatter with a different sized pulley and Belt to the 208's; the 698's used a different molded-type wiring loom to the earlier types. The later Empire Papst motors don't have the same size spindles or spin at the same speeds as the earlier Papst motors
Tho' there is some variance to belt length with various 598's, the earlier 208/298/398's were/are all 35.1 inch belts
Not all 35.1 inch belts are equal, Empire claimed in advertising to grind their belts to a specific thickness. Mark Kellys excellent + informed post will go some way to explaining why some 35.1 inch belts just don't run at the correct speed on an early Empire; belt thickness is critical with these turntablesGrins
Since we know that the motor runs at 1730 rpm at 60Hz a measurement of pulley crown, platter and belt thickness should tell us something.BTW alberto d, the reason a belt makes a difference is that the belt doesn't pull from its inner edge, it pulls from somewhere in the middle. The exact location of this "drive centre" depends on the material and is equal to the poisson's ratio of the material times the belt thickness. Since rubber has a poisson's ratio of 0.5, the calculation for rubber can be simplified to drive ratio = pulley diameter + 1 belt thickness / platter diameter + 1 belt thickness. Since the empire has such a small pulley diameter (around 6mm), changing the belt from say 0.6mm to 0.8 mm would make a 3% difference in speed.
Mark Kelly
Thank you Mark for the convincing and also intuitive answer. That Poisson guy sure kept busy, I remember studying and using Poisson distribution in math classes in college many years ago and had no idea he had so many other things (Poisson ratio, Poisson process, Poisson bracket, Poisson spot, ...) named after him.I bet he'd be into vinyl if he was alive today :-)
http://en.wikipedia.org/wiki/Simeon_Poisson
Alberto
If you have access to calipers, try to get a mesurement of the crown of the pulley and of the thickness of the belt and we'll plug it into the equation and see what speed comes out.
Mark Kelly
My apology but I beg to differYhe inside surface of the belt is what does the pulling where makes contact with the outer diamster of the pulley.
The pulley it's self is a slight bit larger diameter in the center of the belt path, thus by tilting the motor slightly it changes the belt path to a greater or lesser diameter by a very minute amount.
The thickness of the belt isn't going to change this.
BTW the thickness of the belt he has is proper. I personally installed this belt.
Darrell
What you are saying doesn't make sense because it ignores the internal stresses in the wrapped belt.It takes some force to wrap the belt around the pulley, and although this force is provided by the belt tension it is not uniformly equal to the belt tension. There will be some relative compression on the inside edge of the belt and some relative extension on the outside which together serve to provide the bending moment. The neutral point will be determined by how the material distributes stresses, described by the Poisson's ratio. In rubber this neutral point occurs at half the belt width so this becomes the effective drive radius off the pulley.
If you can't see the logic in this, hunt down a copy of the paper by Leamy "Analysis of Belt-Drive Mechanics Using a Creep-Rate-Dependent Friction Law" and read it. I would post a link but the one I have doesn't seem to be working.
This post is the third version, I have been struggling with how to make my point clear.
Mark Kelly
Many aspects have influence on the outcome.Elastisity is one, IOW the amount of force required to give , say 10 percent of stretch in relation the the force needed to do it.
This also would/will have an effect on the resistance to 'bend' around the radius of the pulley.
All this in ADDITION to the effect of thickness and/or width.
Then add to this the affect of temprature, keeping in mind that some things are noticeably more sensitive to temp change than others. Some things are engineered to compensate for this others are not.
The belt sent with this TT in question is of the proper width and thicknesss. I am the person that sold it and packed it and shipped it.
I am as confused as any of what is happening here. I have sold fifteen or more EMPIRE 208/398's with the belts all comeing from the same supplier and without a complaint.
Admittedly something is amiss otherwise we would not be here hashing all this out.
The information comeing to the table from others will certainly help to educate all when addressing problems like this in the future.
No one person can bring together as much useful information as what the group as a whole can. Therefore all comments are welcome!
Regards,
Darrell
link below:
I am in agreement with you!Darrell
There is two different size belts fo the 598's and two different ones for the 698. also the 498 is different.I do HAVE a NEW factory boxed from EMPIRE, conversion platter with instructions and paperwork for a 50HZ conversion kit for a 598 never been used.
The area where the belt runs is machined to a smaller diameter.
It was not later machined this way and the evidence is that the machined part has the anodizid surface.
I'm not sure will ever learn all the quirks of these TT's
Darrell
.
Close to the Edge, down by the river....
-Ray
Thank you for that bit of fascinating Empire trivia about 50/60Hz.Well, that would explain the seller asking for the diameter of the platter, but I don't think that's my problem. I measured it and it's just barely over 12" (12.05").
I am not sure how these motors work, but I assume that if I had the 50Hz platter it would be more than just 3-5% faster. Wouldn't it be 20% or so faster?
Any Empire owners care to chime in? Right now the asylum's money is on a belt that's not close enough.
I am talking about the diameter of the inner rim of the platter where the belt rides.
Close to the Edge, down by the river....
-Ray
On the Empires the belt DOES ride on the outside of the platter.
The international 50HZ version has a platter with a larger inner rim to compensate for the motor speed change.
Close to the Edge, down by the river....
-Ray
The platter you have the picture of is from an EMPIRE 498.This model is different from any other EMPIRE concerning the platter and belt arrangement.
Essentially what it is, is a combination of a 398 and a 598.
It has the 398 spindle and bearing but has the 598 suspension.
It also has the 398 model '980' tone arm unless it has been changed.
Also the sispension spider is cast metal whereas the 598 and 698 uses cast aluminum.
For the 50HX version the belt path is machined smaller not larger.
Also the 498 platter is a ONE piece unit, the 598's and 698's are two piece.
FYI the 498 as you have is the MOST desireable for the AUDIOPHILE and the most rare I might add. I have one of these in the gold finish and one in the silver finish.
Thank you for joining in and for your input!
Darrell
the same with respect to the location of the power light?
I have a feeling I have a real frankenstein on my hands!I bought this beasty to steal the motor out of it and re-sell the parts. Now it looks like I will have to revise my Ebay listing or cancel the ad altogether.
Thanks for the info.
Cheers,
Close to the Edge, down by the river....
-Ray
There is no sush item as a 508Darrell
I am going to post a picture of the platter I have and we can compare. The Empires I have seen, the platter is a single piece, but it acts like a two-piece platter with an inner rim and outer rim. the belt is hidden from view and rides along the inner rim.It's pretty late here and I'm hitting the hay, but I will definitely snap a picture tomorrow and we can compare!
Cheers,
Close to the Edge, down by the river....
-Ray
All of the EMPIRES with suspended platters I.E. the 498, 598, and 698 the belt runs on an inside platter base that is smaller and lower out of site.The 498 platter is a one piece. However the belt runs on a smaller part of the platter underneath and out of site
The 598's and the 698's have an inner and outer part to the platter and the belt runs on the inner part out of site.
Hope this helps.
Darrell
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