Allen TC-4 Project

[Silken Path]

I've decided that the new gyro is too fast. It probably worked fine on a theater organ for flute and reeds, but it's... undignified... for a church organ. I therefore resolve to figure out what speed the big gyro is running at and slow this new one down to approximately match. In other words, make it sound more like tremolo and than a Leslie on high.

Now it's time for turkey, God bless all!

[jbird604]

There's probably a motor available that runs somewhat slower than that one. Or you can change the pulley on the motor shaft to a smaller one. What might be fun is finding a truly variable speed motor like the used on Yamaha Electones with the whirling tremolo speaker. It could run at any speed from a slow chorus to a Leslie-like tremulant.

[Silken Path]

Thank you, John.

Grainger Industrial has a bewildering array of replacement motors available, but I hadn't thought of using a variable-speed motor. Hmm. The DC motor on the Gyro 100 uses a bank of resistors to ramp the motor up in a few seconds. As you know, it's REALLY smooth on these.

This little capacitor-run motor is rated at 1650 RPM according to the placard. These are neat little motors.

I've thought about getting an inexpensive laser tachometer, like the ones that have to have a reflective tape to get a reading, to find out what the RPM is on the big one. There were a few using photocells when I worked on aircraft, but they didn't work all that well. If I can slow the gyro down enough, I'll dedicate both sides of the slip rings to the diapason and put that little cutie gyro on the reeds instead.

I'll have to watch out what controls I add to this organ. Years back I had a friend who had a Jeep and he kept adding accessories like CB radios, light switches, sound systems, winches, etc. to it. Finally he had so much stuff under the dash it endangered both his and his passenger's knees.

***

Ordered a new belt for the gyro - Gates Truflex 0200 47H - $6.52 on Amazon. (Eventually they'll be offering remedial DNA kits and replacement body parts.)

[Silken Path]

Tried something I read about online and flushed the gyro's motor out with WD-40 and let it drain. I got some caked dust/grease pulpy bits out, so I repeated it. Let it drain an hour or so and tried it. The motor is quieter and the gyro has an even longer coast down time now. I think I'll just put the new belt on, make a new rear cover out of plywood, and park this puppy about nine feet away from the organ, where I have a convenient spot. Then I'll pluck some relays out of the '59 to turn on and off the diapasons and reeds to the new gyro.

When these motors wear out, it's going to be a mess keeping these things going. Motor manufacturers are using NEMA frames now, and the smallest standard frame with a 3/8 drive shaft, a 42, is too big to clear the tweeters without constructing a new platform and extending the shaft from the rotor. One used to be able to get automotive crankshafts welded(!). I suspect the same process could add material to the shaft to lengthen it.

However, there's a long pathway from can-do to need-to.

[davidecasteel]

^^^^^ Buy a few spare motors now and store them for use later?

David

[Silken Path]

I should live so long, David. The thing is that since there's no provision for a smooth, quiet startup, it has to run continuously when the organ is on.

[Larrytow]

I'm pretty sure that I have never seen an Allen Gyro cabinet with a rear cover panel on it ( or even near it ). I know they all look like they should have one, and are seemingly set up to add one easily, but having never seen one set up that way makes me wonder if Allen intended them to be open backs for the most part.

The thing to use if you ever need to extend a motor shaft is one of those firm rubber two piece flex coupling motor drive unions. I know they are available in many sizes, but never checked into 3/8"s specifically.

[jbird604]

Some gyros did have a back panel made of Celotex. There are T-brackets mounted on the cabinet to hold them in place, the same way the back panels of many Allen consoles are held on. Lamar, I forgot to give you the back I had for one of those cabinets. If you're ever back over this way ...

[Silken Path]

I'm pretty sure that I have never seen an Allen Gyro cabinet with a rear cover panel on it ( or even near it ). I know they all look like they should have one, and are seemingly set up to add one easily, but having never seen one set up that way makes me wonder if Allen intended them to be open backs for the most part.

Hi, Larry. This one is in a furniture-grade cabinet - more stylish and home-oriented than even Allen's formal church-dress designs. The smaller gyro I have already *has* the back cover. Knock on wood, but the motor is sounding pretty good right now. Oh, and the gyro actually does have a coupling between the flapper boxes.

Thanks, John. I did a search for "Celotex" at Lowes, and it led me to "Insulfoam" garage door insulation - several varieties and thicknesses. I'll look next time I'm in there. A little sound-deadening would be good to knock down the sound from the back of it.

Here's a picture of the amazing amount of gunk hat came out of the motor. The red items are parts of an Arkansas hornet and the circular brown item appears to be a pupae.

[jbird604]

Hahahahahah~! I'm glad you got those out of the motor before they flew out and stung you!

Celotex is a brand name that was used back in the old days (maybe the 40's and 50's) for a tough fibrous composite material that was marketed for use as a layer of extra insulation on the outside of a house as it was being built. We were still calling it that when I worked for my Dad's home building company in the 60's, but the name brand had become a generic term by then. It was probably made of compressed plant fibers, glued together somehow into a rigid panel. Very light in weight, heavier than styrofoam, but lighter than plywood or other manufactured building panels. Could be cut with a sharp knife, though we usually used a Skilsaw.

I'd assume that any kind of dense but lightweight panel about 1/2" thick would work. It did serve to deaden sound somewhat, along with its insulating properties.

A variation on Celotex was stiffer and sturdier and was made into ceiling tiles that could be stapled up or mounted in a suspended framework like today's fiberglass tiles.

[AllenAnalog]

Ah Lamar, it's a good thing we don't live anywhere near each other or we would be up until 3AM every night playing with Gyrophonic Projectors! Haha.

I have a total of 7 furniture-grade cabinets; three tall ones, three medium height ones and one short one. Every one is different. The three tall ones came with my 3-manual analog theater organ. One has a multi-speed DC gyro system for the string voices. One has a single-speed AC gyro system for the flute voices. The reed voices also come through that cabinet but used the electronic tremulant circuit on the Whind generator chassis. It has upward firing cone speakers for the reeds. Both of the tall Gyro cabinets have the Celotex backs. The third cabinet has the traps and pedal voices and had no back. (When I got the organ I was fascinated to see that there was a separate 15" woofer just for the bass drum!)

The other four cabinets were purchased on ebay and they came out of another analog theater organ that was long gone. The owners were just using them as furniture. Two of them have smaller diameter Gyro disks, one AC and one DC. The DC one one has the upward firing Jensen horns, which is one reason I bought the set. I want to use those on my reed channel.

Today I took delivery on a pristine DC Gyro controller chassis that I purchased on ebay. It is the later model and it looks like it just came from the factory, unlike many of the grungy ones I've seen for sale in the past. That will go along with the DC gyro motor and other parts I purchased a couple of years ago to convert my tall flute gyro cabinet to multi-speed. Then I'll have all three voice channels on the theater organ on multi-speed Gyros.

I also have two NOS Allen 29" disks that I got from a guy who purchased them at an Allen garage sale several years ago. They each have three woofers and three tweeters. My two existing 29" disks only have two sets of drivers. It will be interesting to see whether there is a difference in the sound with three drivers. (There is an 8-Ohm resistor in the circuit so that the series/parallel wiring delivers equal power to all three driver sets.)

Once I get settled in my new home (some time in the later part of 2019) I can start having as much fun as you are.

(For those too young to get the reference, this is Gyro Gearloose and his Little Helper. (c) The Walt Disney Company)

[Silken Path]

Thanks, guys. I just draped a heavy old curtain (that I couldn't bring myself to throw a way a few years ago) over 2/3s of the back of the gyro, and it did indeed quieten down the mechanical noises a LOT.

Analog Larry, no wonder it's so hard to find a gyro. You're snapping them up. Sort of like the FF with church organs, but the gyros actually stick to you. (On a kinder not, Larry's is where old gyros go to LIVE.)

I have some "Insulbrite" padding that I bought to make a tush comforter a couple of years ago. It actually made a fanny heater, and I gave up on it. I might try sticking that into the gyro, too.

Larrytow Larry, the back is only covered about 2/3s. I won't be able to look until this gyro is moved out of the way, but I THINK my big gyro has those turn fasteners, too. It's against a wall, so it's no big deal.

[Kurzweil]

I'm pretty sure that I have never seen an Allen Gyro cabinet with a rear cover panel on it ( or even near it ). I know they all look like they should have one, and are seemingly set up to add one easily, but having never seen one set up that way makes me wonder if Allen intended them to be open backs for the most part.

I seem to remember that early speaker cabinets employed what was called an "infinite baffle", which referred to enough panel material between the front and the back to prevent cancellation of lower frequencies. I believe that this is why the early cabinets were far deeper than the speakers themselves required (my large MOS I cabinets). One of their chief advantages was that they tended to be very efficient; did not require a tremendous amount of amplifier power. Then somewhere in the 60's the acoustic suspension speaker was developed. They acheived a similar full sound using a much smaller cabinet but required a great deal of additional amplification. I am not solid on this but seem to recall that Allen's switch to the HC-12 and similar (half the size of before) was accompanied with a conversion from T-50 to T-100 amplifiers (needed twice the wattage). I have a Walker system from a Rodgers that consists of six or so dual 6x9's with tweeters and one large cabinet handling the bass. Probably a fifth the size of the three quads and three duals that the (three channel) MOS 1 920 theater model has. You can see two of the bass bins with a full range above in the photo. That stack is close to the size of two gyros stacked.

I too had those three 1967 cabinets, a two speed gyro for strings, a single speed for flutes with the rotating barrel effect for the reeds, and a pedal/traps cabinet. These were on a 3MT Deluxe, shown in my avatar. They were all open and while not needing to be closed for acoustic reasons, I can see where one might hear less whirring, etc. by covering the backs.

[Silken Path]

Thanks, Kurzweil. Thanks for the photo, too. Although I haven't posted a picture of it and have it packed it away, I also got from the goodies pile at John's place another gyro and a matching half-cabinet that has a T-20 amp, a traps box, and 6 or 8 midranges, and maybe a couple of tweeters.

I've heard "infinite baffle" being used in respect to putting a woofer between two rooms or a room and an attic. It makes sense that an open-back speaker in a large room, loft, etc. would have the same effect in the bass speakers. I'm still impressed at how much sound I get from these 50W amps and ALL THOSE speakers.

My single bass quad is twice the half-bass duo that the gyro sits on. That duo looks like your two bass units in the photo.

Right now, I have the amps all adjusted between minimum volume and maybe 15%. It's a kick thinking that I could pull them away from the wall and maybe get them even louder.

About the theater organ gyro, I'm still ambivalent. Sometimes it sounds smooth like honey and sometimes it sounds hard-edged, abrupt, and too fast for the diapason, which I expect to be somewhat sonorous and dignified. You've given me an idea now about putting the flute on the new gyro to see what that sounds like. (I could then get the big gyro on diapason, which I seem to use as much as any other stop.) I also have a spare T-50 that I could dedicate to the new gyro if needed.

[Silken Path]

I put the new drive belt - Truflex #0200, 20" x 1/4" - on the 317 gyro, and I'm impressed. This quietened it down a lot, and now it's much more appliance-like. I see how it would be acceptable in a home setting. In fact, it's now quieter than the big gyro, but that one was designed to be mounted in a remote location like a choir loft or mechanical room - this kind has to sit beside the organ like Analog Larry's theater organ. Interestingly, LarryTow Larry had a loft to put his heavy 33" gyro and bass unit on.