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AR XA Bearing Well dimentions

B

Birnstengel

New Member
Hi all,

I have an AR XA and an original tonearm. I appear to be missing the delrin tonearm bearing well. I am planning on fabricating one, but I need some dimensions. Depth of well and height from the well to the tonearm pivot point. Also is the diameter of the well hole pretty about the same size as the post?

I have searched over the forum and internet but cannot find the answer.

Thanks
John
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I wouldn't recommend trying to make a Delrin bearing cup. The original all-Delrin cups had a tendency to seize up, and were quickly replaced with Delrin cups that had babbitt metal liners.

You would be better off sourcing a later subchassis with oilite bearings.
 
Or better yet source a cast aluminum T-bar. That may be what gkimeng is saying, I am just not familiar with the term oilite bearings. Marc would have recommended not investing anything into a stamped T-bar. If I recall he said too much flex in the T-bar and wells would freeze up or very easy to crack where the wells connect to the T-bar. I have a couple that I am using for other donor parts such as pivot pins. If you want to try that I have some spare cast T-bars just have to watch for depth of wells for the spindles.
I have a number of extra parts from Marc's inventory and cut Delrin thrust plates
 
Hose53 said:
Or better yet source a cast aluminum T-bar. That may be what gkimeng is saying, I am just not familiar with the term oilite bearings. Marc would have recommended not investing anything into a stamped T-bar. If I recall he said too much flex in the T-bar and wells would freeze up or very easy to crack where the wells connect to the T-bar. I have a couple that I am using for other donor parts such as pivot pins. If you want to try that I have some spare cast T-bars just have to watch for depth of wells for the spindles.
I have a number of extra parts from Marc's inventory and cut Delrin thrust plates
Click to expand...
I would be interested in the cast t-bars and if you have one you don’t mind parting with let me know. I am new on this forum, are you able to shoot me a message and let know how much if you are willing to part.

Oh, I did some reading on oilite, it is mostly ground up copper, with some tin and iron. I was told that the process is to press the ground up metal back together forming a porous metal, the. It is soaked in oil. It is still used for bushings.

John
 
Its a powder metal process. Bronze dust cast under pressure into the bearing shape. Once done, it gets put under vacuum while submerged in oil. When the vac is released the oil fills the voids in the powder and you now have a self lubricating bearing. Tons of fans and other small motors use these. You can get them from McMaster carr for small money
 
If I am not mistaken the delrin bearing wells are different dimensions than the cast aluminum ones. This would mean that you would need the tonearm post and sub platter from an aluminum t bar in order to use it. If I'm wrong, sorry. :)
 
The original AR table used a commercial Babbitt coated insert. Many years ago I found the company that made them, but suspect they're long gone. You can get Oilite bar and make anything you want. It needs sharp tooling so the pores don't get closed over, but it's easy to machine. It comes in two types. The traditional is bronze and expensive. There's also Super Oilite that's ferrous metal and is both stronger and cheaper. Don't know which is a better choice for a TT bearing. IMO, if you use Oilite you want the shaft polished to absolute perfection, or the bearing will be noisy- two rough surfaces make noise. It's hard to make noise when one surface is perfectly smooth. I'd suggest another possibility that's way better than Delrin is IGUS material. A bar of almost any type will work but I like P210. They now sell IGUS material as 3D printing filament, which opens up all sorts of possibilities.
 
Not familiar with that specifically but it looks like you can buy pre-fabricated sleeve bearings made from it. Seems like it would be easy enough to make an outer well from whatever material and press those into it.
 
The earliest AR tables were fitted with drilled, unlined Delrin cups (the bearing bores were just drilled into the Delrin). You can do this sort of thing in applications where precision is not a big factor, for example toy cars, but the precision required to keep a turntable platter spinning true meant that there wasn't enough clearance to allow for temperature expansion and swelling from moisture, and as a result the all-Delrin bearings seized up a lot. The Babbitt lining was the second generation, but the manufacturing and labor costs to stamp a two-piece T-bar, mold two Delrin cups, line them with babbitt and then assemble all the pieces together eventually led to the third generation, a one-piece cast T-bar with press-fitted oilite bearings.

Turntables with the older T-bar had shorter shafts for both the platter and the tonearm.
 
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was it actually delrin or was it nylon? Delrin generally doesn't absorb much moisture and doesn't change dimensions when exposed to it, but nylon sure does.
 
It was Delrin. I was surprised to see that AR cited moisture as an issue, but the earliest AR tables were produced the same year that Delrin became commercially available, so perhaps the formula has evolved since the early 60s. Or AR could just have been wrong.
 
Birnstengel said:
I would be interested in the cast t-bars and if you have one you don’t mind parting with let me know. I am new on this forum, are you able to shoot me a message and let know how much if you are willing to part.

Oh, I did some reading on oilite, it is mostly ground up copper, with some tin and iron. I was told that the process is to press the ground up metal back together forming a porous metal, the. It is soaked in oil. It is still used for bushings.

John
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Sending a message. I have multiple center platters and spindles, will make sure to get the right length or see if yours will work. Older unit with stamped T-bar may not work out so well. Is that first image your table?
 
Here's a question for everyone and maybe it should be a separate thread or put into the AR turntable forum. Please feel free to let me know.
If he is considering replacing the stamped T-bar with a cast T-bar what other issues might he run into? I have Marc's old inventory so should be able to supply spindles of the correct length.
Would the motor be an issue? I don't know if this is a 2 motor unit that we are talking about in this thread.
Any feedback would be greatly appreciated
Thank you!
 
Because of the different bearing depths, an entire inner platter will probably be needed (because very few people have the equipment to pull and replace platter spindles), and a new vertical pivot post.

The two T-bars are close enough in weight and CG that springs shouldn't be an issue.

The motors will not be an issue for a T-bar change, but if the 2-motor is going to be updated to a single-motor an adapter will be needed for the different motor mounting centers, a new motor pulley will be needed because the 2-motor table used 600rpm motors, and a run cap will be needed because the 2-motor table didn't have one.
 
This is a really interesting thread. I'm still learning about my AR XA. I don't know what year it was made, but it's a two motor unit with a cast T-bar. Reading this I'm glad I have the cast T-bar!

Mines serial number XA 64199. Anyone know what year that would be?

(Sorry for the hijack!)
 
There is no definitive reference of serial numbers vs years. The most reliable way to check is to look for a manufacturing date on the motor.
 
Good morning everyone. I am the proud new owner of a AR XA that I purchased from an AK member (thank you John). This is one of the earlier models with 2 motors and has the Delrin tonearm bushings. Works great

For maintaining the Delrin bushings is it as simple as applying some oil/lube on occasions?
 
Maybe some of you fine fellows could help me. My AR-XA is missing the Delrin pads in the arm and platter well. I'm trying to find a source to get some or make some that's not too pricey. Would I need to order a rod of delrin (or other material) stock in the correct diameter and then cut the rod to the appropriate height? Or is anyone 3d printing them?
 
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