DIY Air bearing tangent tone arm

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No.

On the old ladegaard arm the pivot point was at the same height as the stylus tip i.e about 1" below the center of the arm tube.

These arms work better if the pivot point is halfway up the diameter of the arm tube.


Make sense?

It doesnt make much difference where the pivot point is in relation to the arm length as it will be balanced out by the counterweight.
 
Aha, I understand now - the blade pivot in Vic's pics of the Terminator arm is at the center of the arm tube diameter - I presume this gives better stability.

Also, I presume the use of a blade pivot allows an offset counterweight to be used (as per the pics) without any twisting of the arm tube?

Improvements in the physical integration of counterweights to tonearms are often cited as improvement to the sound. I wondered had anybody experimented in this area on the terminator arm. i.e has anybody tried the counterweight at the end of the arm & not offset.

Finally, would the tonearm wire be better coming off at the pivot point rather than at the end of the arm?
 
graeme_uk:

Can you give me some advice..... I have done a fair bit of work on a terminator style arm, but need a little advice. So the pic here gives you the idea:

An externally hosted image should be here but it was not working when we last tested it.



Holes are 0.3mm as prescribed, just used the B&Q alu 25mm angle, got 2 pieces and matched them up (quite a difference in the different pieces well worth doing this). Glued the manifold all up and all is well so far. Today I bought an admittedly el cheapo aquarium pump from my local pet shop. Rated at 375l/h x 2 (ie 2 outlets) and at 1.75psi. However, literally it won't float my boat. A piece of angle will float on the manifold, the carriage, just barely will, but no way will it float when I add the cart, headshell, counterweight etc etc.

So heres my quandary. Do I just buy another el cheapo pump and parallel them, (cheapest way out), or do I spring for the sera 550 that trans-fi recommends?

The thing is that this pump is rated at more than the sera (why I bought it) but at slightly less pressure (1.75psi vs 2.2psi for sera).

What you guys think?


Fran
 
Yeah, at long last I'm getting around to it! It looks ok, and when I hooked it up to a bigger supply it slides really nicely... but just with the pump I picked up today it ain't running. I could get another pump the same and parallel them, but would that work? double the air flow but at the same pressure. Seems that it should but the head is tired at this time!!

For anyone else thinking of going this route, the thing is relatively easy to make, but takes lots of time getting the details right. Only real expense is the pump (assuming you build from scrap lying around)

Fran
 
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Joined 2005
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What I would do is to put some water with dish soap on all the joints in the air path. If there is a leak you will start blowing bubbles. I had a similar problem to yours with a Ladegaard style arm, and poor connections was one of the problems. The other problem was the type of supply hose I was using. Try using the more rigid stuff they use to hook up water filters, and ice makers. Changing the supply line made the biggest difference in my case.

woodturner-fran said:
graeme_uk:

Can you give me some advice..... I have done a fair bit of work on a terminator style arm, but need a little advice. So the pic here gives you the idea:

An externally hosted image should be here but it was not working when we last tested it.



Holes are 0.3mm as prescribed, just used the B&Q alu 25mm angle, got 2 pieces and matched them up (quite a difference in the different pieces well worth doing this). Glued the manifold all up and all is well so far. Today I bought an admittedly el cheapo aquarium pump from my local pet shop. Rated at 375l/h x 2 (ie 2 outlets) and at 1.75psi. However, literally it won't float my boat. A piece of angle will float on the manifold, the carriage, just barely will, but no way will it float when I add the cart, headshell, counterweight etc etc.

So heres my quandary. Do I just buy another el cheapo pump and parallel them, (cheapest way out), or do I spring for the sera 550 that trans-fi recommends?

The thing is that this pump is rated at more than the sera (why I bought it) but at slightly less pressure (1.75psi vs 2.2psi for sera).

What you guys think?


Fran
 
OK,

thanks for that....

I know I don't have any leaks (checked that) but what I do have is a step down just at the manifold to 1/8" copper pipe. That would place a restriction in the air path and would definitely create some back pressure. What I think I'll do is try and remove that so that the airflow is as unrestricted as possible.

Thanks for the hints...


Fran
 
Member
Joined 2005
Paid Member
What type of air supply line are you using? In my case when switched from the aquarium style poly tubing to the rigid stuff, my bearing went from non functional to very good; even with an el-cheapo aquarium pump. Also with that air line, you can use the same compression connection, and loose the 1/8" copper. I hope other builders chime in here, because their experiences will be different.

woodturner-fran said:

I know I don't have any leaks (checked that) but what I do have is a step down just at the manifold to 1/8" copper pipe. That would place a restriction in the air path and would definitely create some back pressure. What I think I'll do is try and remove that so that the airflow is as unrestricted as possible.

Thanks for the hints...


Fran
 
Well, I started off using a silicone type very soft line, but then switched to a bigger more rigid type. The OD of this one is 8mm and the internal dia is about 5mm (shade under 3/8"OD and 5/16"ID). Its definitely better - but I think that piece of 1/8" copper is my problem. I'm gonna aim to get rid of that tonight and see.

See, the more I think about these air pumps... they are designed to give the stated air flow with no backpressure - ie they can only produce that air flow with a free exit. You start putting things in the path and they don't have the capacity to build up pressure.... and in my case it only runs at 1.75psi anyway. So it seems that if you want to use the el cheapo pumps, you need the wider bore pipe with minimal obstructions in the air flow all the way up to the manifold. I went back and looked again at the terminator site and right enough, he uses a fitting right up at the manifold and the pipe just pushes on to it - minimal air flow.

The downside to all this is that if you want to mount your pump remotely, you might need a bigger psi rating. The other thing that I haven't got figured yet is what happens when I add a second pump in parallel - right now as I understand it, I should get 2x the airflow, but only with no restrictions to flow, ie it won't give 2x the pressure.

Anyways, I'll know more later. The shop I bought mine in will take it back if I want and I can always then spring for the sera 550/rena400 as spec'd on the site.


More later,

Fran
 
woodturner-fran said:
Yeah, at long last I'm getting around to it! It looks ok, and when I hooked it up to a bigger supply it slides really nicely... but just with the pump I picked up today it ain't running. I could get another pump the same and parallel them, but would that work? double the air flow but at the same pressure. Seems that it should but the head is tired at this time!!

For anyone else thinking of going this route, the thing is relatively easy to make, but takes lots of time getting the details right. Only real expense is the pump (assuming you build from scrap lying around)

Fran
I use two 250 l/h cheap aquarium pump in parallel; it is just enough to get the arm afloat. I do not think tubing type matters with such low air flow as long as it is bent with large radius and no kinks; just check all connections for leakage.
 
Well I've a bit to go yet. I have the arm wand almost done but the pivot needs attention and then the wiring and the arm lift are yet to be sorted out. Maybe by next week.

The other arm is a modded rega Rb300 with cardas wire and michell tecnoweight. I am curious to see how it goes.


****************

Those who are using these - do you just leave the pump on 24/7 or do you rig up a switch near the TT?
And how important is that buffer tank. The action seems very smooth now without any buffer...


Fran
 
Yep, short arm.. the whole thing is very terminator based. I bought some 8mm carbon fibre rod (8ft length) in France last year (just can't get that stuff here!) for about €3!

I asked in a shop in town once would they sell me an arrow (they had them there in stock). No! told them what I wanted it for, they could cut the head and tail off it..... still NO. Gobshites.


Anyway, I have a fair bit of this left if you need it... although obviously you don't.


Fran
 
I got mine because I found it in the garden one day - brand new - some gobshite obviously shouldn't have sold the arrow to the gobshite that shot it & it landed in my garden!

I held onto it for just this purpose.

Anyway, I've great hopes for this - you know I've always spoken about these arms but never heard one! Good luck with it. I also have some fine litz wire if this might be of use to you - I don't know if this is good for wiring tonearms?
 
Can you guys tell me what youa re doing with your pumps - do you leave them on 24/7 or only turn them on when you are going to listen?


I have done some more work on this tonight and have most of the arm wand and lift done. the pumps are a bit noisier than expected so also need to do some work on them too. Really its just some wiring to go and then I should be ready to mount it on the TT.


Fran
 
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