Hammond CV pitched a few cents below (440)

[thephaedrus]

Background:</p>

I'm located in Canada and looking at buying an organ here. It will be my first Hammond after years of playing clones. It's a CV and it was originally built for 115V and 25 hz frequency. It has a motor to bring it up to speed (as far as I understand) Michael from TrekII said that it probably has a rubber belt without teeth and thus the motor is not locked in and this is the cause of the flatness. I've been reading in this forum for about 2 hours and it seems this problem has come up before for Johnny B3 and others. </p>

Question: </p>

Can you, Johnny, or anyone else, tell me what resolution you came to? Or did you even find a resolution? Any help you can give is appreciated. If there is no resolution, I really can't buy this organ... It sounds amazing though...so I'm really hoping it's possible. </p>

Thanks,</p>

Phaedrus
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[indianajo]

Wow, 25 hz main power. The old Pennsylvania RailRoad standard. I think I saw something about that in my Lionel train transformer manual, but that was the 1950's. Hammonds tonewheels are direct (spring) drive from a synchronous(clock) motor, the starter motor if so equipped is induction and rides along after it is up to speed. They are either on frequency, or usually don't start. You might need to buy a 60 Hz motor to get this conversion up to standard. Check Tonewheelgeneral for part prices, or pick up a $1 M model someplace (there is one for sale right now in my town). My Hammond is dead correct on frequency, I have tuned my piano to it and have started playing along with Long Playing records to train my ear for chords. I think the professional tuner was tuning my piano low to save time and increase stability. I had to retune the piano 4 times before it settled down.

[thephaedrus]

This CV doesn't have a starter switch.. Just a single on/off switch. I'm guessing that's what they call self starting motor?

[johnny b3]

your double post threw me off, didn't see this one at first. My post is a bit grim, but keep your spirits up and we can help each other get to the bottom of a good fix! Also I just got home from a gig, excuse the ungodly hour of this reply.
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http://www.flickr.com/photos/15796603@N02/sets/72157611412531246/ (http://www.flickr.com/photos/15796603@N02/sets/72157611412531246/)</p>

check out my pics, there are 2 of interest that show the motors. Are we talking the same style here? You'll quickly see mine does have teeth and unfortunately here's what my hard effort accomplished: the size of the tooth, plus distance between each tooth (pitch) is different from any of todays standards. Some belts come close but they need to be perfect in order for it to work. Furthermore, no company could even reverse engineer the system by having new pullys fabricated (given the distences between shafts, shaft diameters, belt length etc.) and I was told it was impossible to revamp. To make matters worse, the gear ratio from motor to generator was not 1:1...(12 teeth vs 10, IIRC), making a 6:5 ratio. Your organ probably has the same issue - that being these organs feature a Euro generator (50Hz), originally running on a 25Hz motor with a 1:2 interface to get the generator to A440. With 60hz they needed to step it down, hence the 6:5 deal-e-o. The next idea is that I never heard this organ with its original belts - they tore up long ago...so I can't even confirm that my E ever ran at A440.</p>

So....by now you've figured out that all this Hz stuff is important for the wellbeing of a hammond's tuning. Unfortunately controlling it is tough because the less expensive freq. controllers are not consistant (won't hold perfect freq.) and you'll hear the pitch warble or something...but i've never tested it. TrekII makes a frequency converter for about $400, however I don't think its adjustable - it simply spits out 60Hz no matter where you are. You're already getting 60hz from your outlet so thats not the problem. You need to carefully adjust it a bit higher. Next idea is to get a new motor and go direct drive but if your generator is indeed 50hz you need a 50hz motor (hard to come by). You still need a frequency converter to step down from 60hz. Still pricy, plus factor in the new motor and the time to properly install the thing dead straight, you're back at square one. Lets not even get into replacing the generator...So you get the picture...we're quickly seeing how the organ should be loved as is...it quickly becomes a matter of the fix being more expensive than the organ itself. </p>

For the model E, my last ditch effort was to use o-rings. This made the organ playable however it is far from a perfect soloution. The lack of teeth is the major issue, i'm positive there is slipping and inconsistant power transfer between the two shafts keeps the pitch untrue. (Main generator is about 20 cents flat, chorus generator is way off...a few semitones which makes it completely unusable. sounds like a dying cat and breaks my heart.)</p>

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Where are you located? Fill us in on the details of your CV's drivetrain, pictures if you can.
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[thephaedrus]

Thanks JB3! I'm so glad to hear your feedback. I was going to be paying $1850 CDN for the organ, a modified Leslie 101 with upper rotor, 2 speeds, jensen driver, tube amp along with a Leslie 120 with an added tube amp. </p>

I've decided that I can't live with this organ without it being 440....unless the price is significantly lower....since the cost and effort to fix it seem large. </p>

This morning I also heard from Captain Foldback who confirmed that the price was not worth the trouble even though it probably could be fixed. From reading your posts, it sounds like you've definitely put in the effort and time and your experience has been informative. It has been extremely hard finding information about these "northern hammonds" as I'm sure you appreciate and it seems that you are the single person on the internet who has truly gone down this rabbit hole and taken the pictures to prove it. :) So thanks. Looks like I'm back to the drawing board.....with a little more knowledge in my belt. I'll definitely have a better idea of what I'm looking for now, a little more caution, and a much more thorough examination of the particular Hammond. It will be tough walking away from this one. The organ did sound sweet!
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[dunderola]

It cannot be that hard to fix..As i live in a 50Hz area and got hold of a 60 Hz M3 i bought a frequecyconverter for about 130$ (99euros)..115 volts50Hz in...straight to a rectifier..then some electronics..and voila..115 volts 60Hz adjustable out..ca 3 or 4 notes plus or minus..</P>


With that in mind..im sure the same converter can take 60 Hz in and give adjustable out..maybe from 55 to 65 Hz.. only thing is that if the changed motor is more powerconsuming than the converter can give..</P>


Ola</P>
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[thephaedrus]

I think your situation is different. My area is already 60hz. The organ was made for 25hz back in the day and modified to run on 60hz. Problem is, the modification is off. The belt that drives the motor probably isn't grabbing properly. The guy at TrekII said their converters won't do the job for this situation. From the sound of it....this CV isn't worth the $1850 CDN it's going for. (along with a modified Leslie 101 and 120.) The 101 sounds pretty darn good. The guy put an upper rotor and jensen driver along with a proper tube amp. I think the effort is not going to be worth it. It might be worth it if I can get the whole package for $1000.
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[indianajo]

$1850 canadian is pretty rich for a CV, but the problem is not unsolveable. McMaster.com sells toothed rubber belt timing pulleys in, for example, the 24 tooth size and the 20 tooth size for 1/4 wide toothed belts. The pulley belt od diameters are repectively 1.528" and 1.273", coming out to, my calculator says, 1.20003 ratio. So if you put the 20 tooth pulley on a 60 hz synchronous motor, put the 24 tooth pulley on a 50 hz tone generator, and built a sliding mount to move the motor around to tighten the belt, you should be able to get the right tones out of a 50 hz tone generator with a 60 hz motor on 60 hz power. No fancy electronics required. A spring coupler as Hammond used on their tone generators in their standard application should smooth out any cogging vibrations, you might need an idler shaft riding on two pillow block bearings to give you something to hook the spring coupler to. Spring couplers are also available from mcmaster. Of course, this is all theoretical since the questioner decided the price was too high.

[johnny b3]

If you can solve this for me i'll be pretty darn happy. here's the beef: You can't move the motors away from the drive shaft...at least not at this point. They're too close together to put on new pullys of your given dimensions. Here's what we're starting with:</p>

Original Belt:
</p>

Width: 3/16"</p>

Pitch: 6mm</p>

Teeth: Roughtly 19 trapezoidal teeth </p>

Motor shaft diameter: 8mm
Generator shaft diameter: 4.8mm (0.18")
Distance from outside of shafts: 31mm


Motor pulley:
10 teeth
18.8mm (0.725") outside dia (peak to peak)
15mm inside dia (trough to trough)

Generator pulley:
12 teeth
22.5mm outside dia (peak to peak)
19mm inside dia (trough to trough)


outside circumference around both pulleys: 4.675" </p>

One pulley has a hub (side walls).
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If I were to CAD this, you would see that the 31mm shaft offset results in the pulleys practically touching one another. The hub on one pulley almost overlaps the adjacent pulley. So you see...McMaster has nothing that can brave this storm. </p>

Even if we somehow get a belt, or new pullies there is a near certainty we won't attain A440 so a variable frequency drive may still be necessary. But i'm willing to settle if I can get both generators in sync. I don't believe there is enough room in the chassis assembly to move the motors farther apart. If there is enough clearance inside the cabinet to do this, an entirely new chassis would need to be fabricated.
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[thephaedrus]

Thanks everyone, JB3 and organforum just saved me $1800. I called
the guy and told him I couldn't take it. He was a nice guy and really
good about it. I gave him $50 for his trouble since he moved the
Leslies out for me.

[indianajo]

Again, this is all sort of theoretical since Mr. Phaedrus has indicated he is not going to start this project. Lets assume the tonewheel generator is designed for 50 hz power, probably designed for 1500 rpm, and the replacement motor turns at 1800 rpm on 60 hz power. Motor shaft diameter of "8mm" is pretty close to 5/16", I'm sure a 60 hz motor would actually be 5/16". Mine is that dia in the H. Tonewheel shaft diameter of ".18"" is more probably .183" or 3/16". Mcmaster sells 1/4" timing belt pulleys in both 3/16" and 5/16" diameter hubs. If there is not enough pulley selection in the 3/16" hub to get a 6 to 5 ratio, , one could buy a bushing for a bigger hub pulley and drill a hole in it for the setscrew. The original pulleys and belts should to be pitched, modern flat belt have a modern cog profile, and it sounds like, many more cogs per inch of belt. I don't have access to a CV to see the clearance problems, but if one is willing to drill a few holes and saw some slots in sheet metal, a sub-chassis could be fabricated to hang the motor up in the air, (I have a foot of clearance overhead in an H) or out the back if necessary. If hung out the back on a swivel (to keep the belt tight) the motor should be covered by a little box to keep fingers and hair out of the belt pinch point. Belt tightening should be confirmed by pushing against the sub chassis with a long threaded screw. Probably to solve cogging vibrations of the timing belt, a jackshaft should be installed on a separate little chassis on two pillow blocks to carry the driven pulley, and install a standard Hammond type spring coupler between the jackshaft end and the tonewheel generator. The jackshaft sub chassis should have slots in it to allow movement to line up with the tonewheel shaft, and standard motor shims or stacks of washers to align the bearings vertically. Any factory mechanic knows how to use straightedges to line up motor and load shafts. I imagine hammond installed 4.5" dia pulleys to solve cogging vibration, but smaller pullers should be fine if a spring coupler is installed to remove the vibration. Any thoughts?</p>

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