| Tee-Rex |
Hullo,
Below attached is a design for a table I'm going to build.
Plinth material - high density aluminum alloy, leadshot damped.
Platter - Acrylic topped with teflon. Leadshot damping is an option I'm considering.
Bearing - All bronze. Ceramic ball and haven't decided about the thrust plate yet.
Motor - DC pll controlled - maxon or like.
Arm pod - same material as the plinth but haven't decided on the arm board itself yet. I was considering carbon fiber.
So, first, I'd appreciate comments on the design. Plus, specific suggestions on:
Arm board material?
Thrust plate material?
Thanks,
-T |
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| livemusic |
T-rex,
1. Bearing - way too small. You have to deal with complex vibrations, caused by large and imperfectly balaced rotating mass, with the side load appied (belt tension). Look at the Teres/Galiber bearing - they have a large diameter and substantial lenghts, in order to stabilize the platter and absorb vibrations by means of the oil layer, spreaded along large contact area.
2. Armboard - I made one for my friend from aluminum-acrylic-aluminum sandwich, bolted together. It cost me 300 sheckels at one of the south Tel-Aviv local workshops and does very good job.
3. Feet - fix the ajustable rods with the counter nuts and make the supports wider. It must be very stable/rigid in both planes.
4. Motor - I'm happy with the Teres motor/controller, but the controller may be superceeded by simple variable resistor. Do not go for a cheap motor though - it is a critical part.
5. Platter - lead shot loaded platter is way superior.
6. Thrust plate - I use delrin, but ceramics/tungsten may be better.
Good luck with your project! |
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| Tee-Rex |
Speaking of Galibier - anyone have an idea why the multiple screws on top of the Galibier and Redpoint platters?
Livemusic - do you mind if I drop you an email?
Cheers
-T |
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| livemusic |
T,
Galiber stuck with idea, that bolts are superior for the platter layers connection - make sence, but the bolt heads are not necessary to be exposed, compromising platter-record contact, IMHO...
You are welcome to email me.
Shalom,
Michael |
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| InDaGroove |
Not much time this morning to cover everything, but two things...Thrust plate- if the ball is off center just slightly, hard surfaces are not good. I was using Ceramic/Carbide, and had this problem. The ceramic ball actually ground a divot into the carbide, and a small flat appeared on the ceramic ball. I went back to nylatron (google it) for a thrust plate, and I can send you some if you would like.
Multiple screws- I have a teflon top layer, and used 48 screws. Teflon is not stiff- if enough screws are not used, it will "come up" (for lack of a better description) between the screws, especially if the mating surfaces are not dead flat to begin with.
Colby |
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| Tee-Rex |
Thanks Colby.
I'm attaching the newer plan, after many hours of thinking and reading a lot of info. I some how came up with some parts very similar to the Teres principles. Chance or fate? Some things just make sense to me.
Anyways, wrt the platter. Leadshot filled and topped with Teflon is the plan. Either Acrylic or aluminum platter body, still considering. I thought gluing the teflon on top of the platter body. Do the bolts really make a difference?
As for the thrust plate - I believe the platter will reach 15-20kg. Would the Nylatron hold? How does it compare with Derlin? Thanks for the offer on the Nylatron, btw.
I was thinking to center the ball using a recess in the bottom of the bearing shaft. What I don't understand is why does the ball need to have minimal friction with both upper and lower surfaces. I'm thinking it can be held tightly by the shaft recess, and spin freely on the plate.
TNX
-T |
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| InDaGroove |
The design looks much better- not much I can add, but if you'd like to see my design and pictures, they are in a nearby thread "intro from newbie TT builder".
Gluing teflon sounds next to impossible, although McMaster-Carr does carry an adhesive that will bond teflon (spendy, I think).
I came across a chart of plastic characteristics today at work, and discovered that nylatron is not the best material for a thrust plate. Here are some comparisons for you...
Compressive strength (10% deflection), PSI: (higher is better)
Delrin 150 (Acetal Natural)- 18,000
Delrin (Acetal Teflon Filled)- 13,000
Teflon- N/A (Forgetaboutit!)
Nylatron- 10,000
Peek (very spendy)- 17,000
Phenolic (bearing grade)- 50,000
Cast Acrylic- 17,900
Ultem 1000- 22,000
Coefficient of friction (Dynamic): (lower is better)
Delrin 150- .25
Delrin- .14
Teflon- .07
Nylatron- .13-.16
Peek- .34
Phenolic- .21
Cast Acrylic- N/A
Ultem- N/a
I brought home a piece of Ultem today and swapped it with the Nylatron. As an experiment, I counted the seconds it took the platter to reach a dead stop after turning off the motor (Teres).
Nylatron- 28 seconds, Ultem- 40 seconds
I was goin to include a comparison of the divot produced, but it appears that my ceramic ball has indeed developed a small flat on the bottom from grinding against the carbide. But it looks like the Ultem holds up much nicer.
Your other question about the ball turning against both mating surfaces, I can't comment on. My ball is press fitted, and only rotated against the thrust plate. Seems fine to me.
Colby |
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| Tee-Rex |
Now this is very interesting information. As always with engineering, it looks like you need to trade off between srength and friction when choosing between these material.
I have read through your thread more than a couple of times... I think it's one of the most interesting pieces of work I've seen around the DIY pages. I do regret no pictures of the final result though:xeye:
Anyways - is your thrust plate flat (was it originally before the divot, I mean...)? I just wonder if the ball is press fitted into the shaft (or, come to think of it, is worked as an integral part of the shaft, that is the shaft comes with a small sphere in the bottom), would the ball still stray off center.
-T |
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| InDaGroove |
I think that friction is not such a bad thing in the thrust bearing, as long as it is quiet and consistent. I may be wrong. For the same reason, I feel that heavier oil is better, especially for a high mass platter. It helps maintain constant speed just as inertia does- while inertia keeps the platter from slowing, drag keeps it from speeding up too quickly when the motor is making a speed adjustment.
If the ball is press fitted into a hole in the bottom of the shaft, and it is on center, it will not move off center when rotating on the plate. The hole must be bored, not just drilled, on a lathe, after indicating in the shaft, unless both features are machined at the same time.
My thrust plate is flat and parallel. I made it on a lathe, but facing on a lathe always creates a small "***" in the center, especially if the tool is not on center, so the surface needs to be lapped flat on fine grit sandpaper to make sure it is smooth and flat.
Cheers,I was just looking at your design again. The interface between the shaft and bearing is fairly long. Take a look at mine and see how I'm actually using two bearings, near the top and bottom of the shaft. That provides the same stability, but reduces the size of the interface (and drag), and allows oil to migrate through easier. You might want to consider reducing the shaft diameter in the middle section. Keep in mind the assembly procedure- you want to still be able to guide the shaft into the bearing without mis-alignment which could damage the surfaces.
Cheers,
Colby |
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| Tee-Rex |
You are right Colby - my head is still spinning from reading some of the Teres threads (oil sump size and should it be worked into the bushing or the shaft, high or low viscosity oil, material of thrust plate etc.)
Anyway, I was going to add an oil sump - say work 1-2 mm into the wall of the bushing at center height, for ~50% of the contact area.
-T |
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| Vinyl-Addict |
I'm curious why the interest in teflon as a platter material?
BTW, I spoke with the Galibier designer about 2 (perhaps 3) years ago about why he decided to bolt the Teflon from the top.
He said because he didn't think that Teflon would hold threads well. That is completely untrue, IMO. I would never build a table with the platter bolted from the top.
Think about the swiss cheese design. The record is coupled directly to a surface with about 48 or so empty spaces below it. As the stylus passes over those areas you would think that vibration would increase due to the unsupported area where the bolt head is. This cannot be good.
As far a thrust plate material, if ceramic doesn't work for you try heat treated PH 17-4 stainless or heat treated 4140. |
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| Tee-Rex |
Vinyl-addict,
Well it's a mechanical impedance matching thing. You get vibrations transmit better through the plane where the record and the platter meet, thus damping stylus generated record vibrations. Since the mechanical impedance between vinyl and teflon matches (as do PVC, and to a lesser degree acrylic), mechnical waves transmit easily to the platter where they are damped, rather than being refractured back into the record and the stylus in turn.
See here
BTW, makes u think why not a vynil platter - but I've seen little or no advocats for those, so decided to take the teflon route.
PVC is great btw - I have a heavily moded Thorens 124, in which the thin aluminum top platter was replaced by a ~2" solid PVC. It works very very well.
I tend to fully agree with u about the swiss cheese thing, although I wonder if the effects wont be negligible. I do intend to do my best to bond the teflon to the platter w/o screws.
Thanks for the tip on the bearing. Were u refering to the ball or the plate?
TNX
-T |
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| B Cullingford |
Teflon is of course very hard to glue - though perhaps there is a special glue ($$$$?).
Many years ago I used some specially etched (I believe) teflon sheet which could then be glued with 'normal' glue, the glue holding on to the tiny holes. I had it to replace cork pads on an oboe (not sealing pads but for adjustments) and I got from a oboe repair place. I might even have a small piece left, somewhere.
I do not have any idea where to get teflon treated this way now but perhaps if you know it exsists a search would be sucessful.
Or maybe you could etch it yourself! |
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| Tee-Rex |
Sounds like worth pursuing. I was actually playing with the idea of playing with the teflon layer bottom in some way in order to facilitate bonding.
I just started wondering what if I just place it on the aluminum platter w/o any bonding - sort of like a mat (a 1cm mat, though). Actually, I can apply some stress in the middle (from the spindle shaft) and from the perimeter (the ALuminum actually being recessed in order to contain the teflon layer. I'm concerned though that pressing though without any pull at the bottom will eventually make the teflon concave, especially as the temperatures change.
I was even playing with the idea of a simple vacuum pull between the 2 layers - but seems too complicated.
-T |
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| InDaGroove |
Thanks for the explanation about the teflon, Tee-Rex. I wasn't quite sure myself why I chose it. I know it is dense and heavy- when you knock on a piece of it, it replies with a dull thud. I knew I didn't want vibration travelling through the platter and reflecting back to the record. I originally used a piece of clear PVC, which is vinyl, for the same reason.
The teflon is very easy to machine with a good surface finish, resists almost everything chemical, cleans well, and basically just looks cool!
Only 40 of my 48 holes are under the record, and I used the smallest screws I could trust (4mm socket-head cap screws) and the counterbores for the screw heads are .250 dia. I think that the swiss cheese effect is quite minimal, especially since I am using a reflex clamp that seems to be working quite well.
Tee- will you be doing the machining yourself? And what CAD software are you using?
Colby |
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| Vinyl-Addict |
| quote: | Originally posted by Tee-Rex
Vinyl-addict,
Well it's a mechanical impedance matching thing. You get vibrations transmit better through the plane where the record and the platter meet, thus damping stylus generated record vibrations. Since the mechanical impedance between vinyl and teflon matches (as do PVC, and to a lesser degree acrylic), mechnical waves transmit easily to the platter where they are damped, rather than being refractured back into the record and the stylus in turn.
See here
Thanks for the tip on the bearing. Were u refering to the ball or the plate?
TNX
-T |
I have read many an article regarding mechanical impedance but never one that directly addressed the specific matching to vinyl explicitly, only theory is discussed, as was the link you just offered.
Anyway, have you or anyone you know tried using ABS as a material? I machined 2 platters a couple of years ago, 1 acrylic, 1 from ABS(mainly because I had some ABS laying around the shop), and guess what, I prefer the ABS platter. Before I made it I was to believe that acrylic was the better choice but after hearing the 2 materials, swapping back & forth, I much prefer the ABS platter, to each his own. Acrylic, in comparison is grainy, promotes more surface noise, and is just not as smooth in presentation, in my system at least.
I was referring to a ceramic thrust plate. I mentioned PH 17-4 because you can machine it, then have it heat treated to R62, surface grind it, polish it, and you'll have a great surface for your bearing to ride on. |
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| Vinyl-Addict |
Acrylic platter on a P3.
ABS platter on a P3.
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| Tee-Rex |
| quote: | | Tee- will you be doing the machining yourself? And what CAD software are you using? |
When this design started it was mainly based on wood - but one thing led to another, and I ended up with mainly aluminum. Since my machining capabilities are somewhat limited, I figured I'll do the simple things myself, and have a friend of mine do the more complicated stuff. The bearing is a whole different story - I'll probably pay a precision machinist to make the parts - or, buy a teres or equal bearing. I'm just not sure that getting a machinist to match the Teres spec (0.2 micron smoothness, 5 micron clearance) will cost me less.
On CAD SW - I'll probably do AutoCAD - don't have it myself but have easy access to a PC which has it on. Any other recommendations (for freeware...) are welcome. The drawings I attached earlier are with Visio.
| quote: | | Anyway, have you or anyone you know tried using ABS as a material? |
No, but I'm not surprized it sounds better than acrylic. It looks like a very sensible choice, and I guess your listenning experience prooves it is. btw, the platters look gorgeous. Is ABS easy to machine?
-T |
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| Vinyl-Addict |
| quote: | Originally posted by Tee-Rex
Is ABS easy to machine?
-T |
Yes it is, very easy. The only thing to keep in mind is that these materials are stressed and when they are machined, they "move". IOW, after you machine the plastic, it will not be completely flat. You can either anneal it prior to machining or rough machine your platter(leave 0.02-0.03 all over), then finish machine for maximum results and minimal runout.
You could make your own bearing by purchasing Ultra Precision Ground shaft and pressing the shaft into an aluminum subplatter or bearing hub. If you look at the picture of my acrylic platter, you can see the bearing hub I machined underneath. I used ultra precision ground shaft for the bearing axle.
The Teres bearing does have a beautifully ground surface that costs plenty as a secondary operation. Unless you have several bearing axles for grinding, the cost would be too high for a "one off" bearing such as yours so the choice is yours, build your own with ground shaft or design your table around a Teres bearing.
Good luck, Frank. |
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| Tee-Rex |
Thanks Frank and all.
I'll be back when there are some pictures to show.
Cheers :clown:
-T |
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| InDaGroove |
Tee- Just wanted to let you know that I bonded a piece of teflon to a piece of aluminum with RTV silicon adhesive. I just spread out a good bead of it to get full contact when clamping it. Now that it has cured, I can't pry it apart. The layer of adhesive is about .015" thick.
The only problem with doing this with your platter is that if you ever want to try a different material, like wood, etc, you would have to machine it off. Also, how does a layer of adhesive afffect resonance??
Colby |
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| Tee-Rex |
Wow Colby - that's really interesting. I never thought RTV would hold to the slippery teflon.
Most of the places I found on the Net that talk about bonding teflon, state that some kind of etching needs to get done to the teflon surface prior to bonding - whether by chemical or physical means.
Anyways - I'm no expert but here's my intuition on the adhesive layer effects on the platter sound FWIW:
Assumption - you would like it not to be there - in the sense that it wont have any audiable effect. However, if it does have an effect, you want it as minimal as possible and as uniform as possible. That's why I believe you want the adhesive layer to be:
a) Thin
b) Uniform
c) Rigid (more or less like the materials it bonds)
I'm sure it affects the overall mechanical response of the platter, but have a gut feeling that if all 3 parameters are kept to sensible levels, it'll be inaudiable or nearly so.
Just a lousy electric engineer's take on mechanical stuff, though - I would ask the experts:D
-T |
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| livemusic |
| I would not use any compliant material like RTV, within mechanical vibration path, including platter, bearing, base and feet. It affects adversely the sonic signature of the whole assembly. On my splitted platter, I placed once the layer of sorbotane on the bottom side of the upper plate, which was rigidly coupled with the subplatter. Sorbotane sucked the whole life from the music, without even being included directly into vibration path. |
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| Tee-Rex |
Thanks livemusic.
Using RTV would not have made it due to parameter (c) in my list above (rigidity). However, I found it interesting that no etching had to be applied to the teflon, as etching would risk, IMO, parameter (b) - uniformity.
-T |
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| Tee-Rex |
Hey, I was just browsing through some old posts.
Did anyone end up trying to load the top platter on the subplatter using cones?
I've noticed that FDEGROVE was suppotive of this method. Frank?
Cheers
-T |
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| Tee-Rex |
:scratch:
I'm a little worried about the cone stuff. The platter is 2" aluminum topped with 1" teflon. If I get the teflon layer to rest on cones, I'm afraid I'll create more problems than solve ones.
My problem is that the teflon layer is light and not self damping. Now, if the cones were real ideal mechanical diodes connected to a mechanical ground (the self damping aluminum+leadshot subplatter), then I'd be fine. But cones aren't. They are not infinite resistance for vibrations going up since some waves will find their way to the point contact with cone, and more problematically, they are not zero resistance on the way down - waves will travell awhile in the teflon until they find their way to the small cones and then they still need to cope with the impedance difference between the teflon and the cone material. Under these conditions the fact that the teflon layer is light and resonant will likely kill the solution. I think I'll better find a way to fully engage the teflon to the aluminum sub platter and rely on the self damping of the subplatter, bearing, plinth and rack to "ground" the vibration.
I still would like to avoid glueing or bolting. How about stress fit? The aluminum would have multiple small cylindrical protrusions and the teflon will have matching bores, slightly deeper than the protrusions hight to allow full contact of the 2 layers. You lower the teflon onto the aluminum, apply some pressing and viola - the teflon locks in place. Would that work or would the teflon "travell up" with time due to it's slippery characteristics?Maybe a small taper in these joints to create and mechanical lock? Thoughts anyone?
Cheers,
-T |
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| Vinyl-Addict |
| quote: | Originally posted by Tee-Rex
:scratch:
I still would like to avoid glueing or bolting. How about stress fit? The aluminum would have multiple small cylindrical protrusions and the teflon will have matching bores, slightly deeper than the protrusions hight to allow full contact of the 2 layers. You lower the teflon onto the aluminum, apply some pressing and viola - the teflon locks in place. Would that work or would the teflon "travell up" with time due to it's slippery characteristics?Maybe a small taper in these joints to create and mechanical lock? Thoughts anyone?
Cheers,
-T |
Not a good idea. As a machinist speaking here, I see too big a challenge to hold the very close tolerances involved here. It's also a waste of time. Thermal expansion of both materials is very different.
Teflon is not a good material to bond, pressfit, and for that matter has terrible "creep" qualities.
I build precision Teflon parts as part of an assembly for NGK America, can't go into details here but I know quite a bit about Teflon. I'd stay away from it, just my opinion.
If you must use it in your application, thread it, and bolt it from the bottom of the aluminum platter and use prestressed bolts and an inch pound torque wrench to bolt it together. Have the machinist bolt it together in a controlled environment (68 degress F) and take a finish cut across the face of the teflon and that's as good as it gets. If you assemble it any other way, no guarantees of flatness over time. Good luck.:) |
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| Tee-Rex |
Thanks Addict.
Oh well - I guess I'll start looking into other materials than teflon. Too many issues to KISS. :cannotbe:
May be I'll take the PVC platter off the Thorens and play with that a little.
-T |
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| Tee-Rex |
Another issue:
WHY is it that designers damp with 12 (or so) symmetrical circular spaces filled with leadshot. I mean, I'm sure that compromizing the homogenous structure of the platter is not good for the balance - why not keep that to a minimum by constructing 1 concentric "chasm" and fill that with leadshot (make it close to the platter boundary for better inertia). That way, radialy you still have a varying structure, but at least it's tangentially symmetrical. Like in the picture attached.
Anyone?
Thanks
-T |
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| Tee-Rex |
Found this link that talks about speed accuracy and vibration control (the topic is the Rockport seriusIII but theres only theoretical discussions in the content).
Pretty basic stuff but very thoroughly analyzed in a very descriptive language. I think it's worth reading.
Here
-T |
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| InDaGroove |
| Wow- Long read, but very informative! Made me realize why sometimes I think it sounds like my platter is slowing down. If I don't have the record clamped tight, I think it might be slipping on the teflon. I have to have it clamped just to brush the record! Another drawback to teflon. I think I might need to have a go at some other material for the top layer. |
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| Tee-Rex |
I thought about this and decided to keep posting thoughts - although not always getting answers/comments. It's OK - it may be boring to people, but it helps me think straight. So, here goes:
The link above got me thinking about vibrations in the tangential direction and the idea of separating top platter from sub platter with cones. The sub platter (2" alu) is heavy and self damping (high enertia, leadshot, bearing oil viscosity etc.). The top platter (1" PVC for the time being) is rather light with little or no self damping ability. I'm assuming a few things to be ideal for the sake of this analysis:
1) Vertical vibrations are handled by the cones acting as mechanical diodes. Hence, I will only analyze horizontal movement, and specifically tangential one, which is actually the vector element being translated as effecting speed stability
2) I'll assume that the bottom platter has an infinite ability to damp stylus induced vibrations. However, it's still causing it's own vibrations.
3) Top platter and record are regarded as one mechanical unit.
Now the target is twofold - vibrations coming from the stylus should be fully transmitted down to the sub platter where they would be mechanically "grounded". But vibrations from the sub-platter (coming from motor, belt, bearing etc.) should not travel up to the top platter-record-stylus. After giving that some thought, I've come to think it's impossible. That is because, as Einstein noticed, there is no difference between top platter moving wrt the sub-platter and the sub-platter moving wrt top platter. That was a discomforting thought, but then I realised something else. There is a difference between the 2 types of vibrations (and remember we're talking tangential direction only). While forces coming from the sub-platter have all the reasons to statistically of the same amplitude to both sides (that is, want to slow and speed up the record at the same level when averaged), stylus induced forces are only in one direction. That is, there is the force the stylus exerts when meeting a loud passage in the groove that wants to slow down the turning of the record, but coming out of the slope in the vinyl, it won’t really try to "push" the record to go faster. Thus the stylus only creates a drag force, an a-symmetrical one, and assuming the sub-platter applied forces are symmetrical, it's safe to assume that the average composite vector applied to the interface between the 2 platter parts is not zero, but is actually a vector that wants to slow down the platter.
I think that it would be beneficial in that case to make the interface between the platters a-symmetrical in a way that makes the system reject dragging forces more than it rejects speeding forces. The balance point between tradeoffs can be optimized.
So I attached 4 diagrams. They show the record spinning and the stylus hitting a loud passage. The blue arrows show the forces working – sub-platter forces going both directions and stylus forces going one way. The red arrows, OTOH, show the vibrations in the top platter (and hence the record) resulting from these forces given the different damping abilities of the different system parts. Figure (a) shows what happens if the platters are tightly coupled (bolted or glued). Given the assumptions I described above, 100% of the sub-platter induced forces will translate to vibrations in the top platter, where as the stylus induced forces are TOTALLY damped by the full coupling to the damping sub-platter. Figure (b) shows the top platter resting on cones, residing inside spherical bores in the sub platter. Any horizontal movement of one platter wrt the other is somewhat damped by the cones needing to travel up the spherical slope, thus working against gravity. That’s why the red arrows are slightly shorter than the blue ones.
Figure (c) takes advantage of the knowledge that there is more drag than push force – one side of the bore is completely coupled to the cone – totally preventing stylus dragging by transmitting all of it to the damping sub platter. On the other hand, subplatter induced forces in this direction will also be fully transmitted upwards with zero damping. The opposite side of the bore is as spherical as in figure (b), allowing the same partial damping for vibrations in that direction coming up from the sub platter to the top platter, and compromising nothing in terms of transmitting downwards going vibrations, as these are non existent in this direction.
Figure (d) is a compromise between the (b) and (c). Both sides of the bore are spherical – but the one that needs to damp down-going stylus drag forces has a noticeably stronger slope presenting more damping in this direction than the milder slope on the other side dealing only with sub-platter induced forces.
I think solutions c & d are better than a & b – but not sure. Also I don’t know how machinable this is. Now if anyone had enough patience to go through this tiresome explanation – I’d appreciate your views.
Thanks
-T |
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| B Cullingford |
Tried to read that thesis on motors - lots of impresive words but I'm sure I think it all correct - way to verbose for me to wade through especially since I'm not making a turntable.
One example: not all motors do the kick and coast thing - for example a stepper motor driven by a quadrature sine waves (90° phase) has constant drive - this effect is used to do micro stepping. Then the worry is how perfect is the machining - ie are all the steps equal.
I also do not agree with the premise that the cartridge is responsible for the amplitude - the platter, plinth do not vibrate???? put the stylus down on a turning record and listen to plinth using a screw driver as a stethascope (spelling?) - And the turntable responsible for all the timing, is the cartridge perfectly stiff in the lateral (with the groove), that is it does not move at all (this is probably nearly true). The article talks about the cartridge effecting the speed - do different cartridges behave differently?
Anyway I did not have patience to plow through all that stuff - some is probably good - just easier to think about myself, which means that maybe I'll miss the pearl of wisdom in there!
Bill
For some unusual ideas on tt design study the Well Tempered Turntable - I like many of its features and the bearing design would be easy to DIY. Oh and ignore the Stereofile comment that it lacks a suspension - it does not - it does not have a bouncy one but that is a feature! - I believe that long article mentions some of the speed problems that can arise from motor and platter moving relative to one another.
I'm biased, I own one - put together from various bits left over from customers upgrading many years ago and a few new bits, and some custom pieces. Some day I'll make that custom motor supply I designed so many years ago. |
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