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Old 4th January 2009, 06:51 PM   #21
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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.
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Old 4th January 2009, 07:45 PM   #22
jkeny is offline jkeny  Ireland
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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?
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Old 4th January 2009, 09:11 PM   #23
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The counterweight was offset purely as it was easier to add the threaded rod that way. Theres no reason why the counterweight cant be on the end of the arm wand.
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Old 9th March 2009, 11:56 PM   #24
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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:

Click the image to open in full size.


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
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Old 10th March 2009, 12:19 AM   #25
jkeny is offline jkeny  Ireland
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Aha, Fran you're doing this arm - just can't keep up with you. But I have to say all your work looks & sounds great & I've no doubt this will turn out the same.
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Old 10th March 2009, 12:25 AM   #26
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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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Old 10th March 2009, 03:08 AM   #27
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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.

Quote:
Originally posted by woodturner-fran
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:

Click the image to open in full size.


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
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Old 10th March 2009, 09:51 AM   #28
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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
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Old 10th March 2009, 01:04 PM   #29
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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.

Quote:
Originally posted by woodturner-fran

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
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Old 10th March 2009, 02:31 PM   #30
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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
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