ct0517, raw BS I'm afraid. Just what is that horizontal bean going through the air bearing? A perfect vacuum? It may have less horizontal mass than other linear arms but there is still a marked discrepancy. It is IMHO the best design for an air bearing arm almost identical to the Walker. Wonder why they stopped making them? Anyway I am still of the opinion that the best way to do a linear tracker is by having the horizontal axis servo driven. The physics of the situation does not change just because you do not like it. It should be horizontal effective mass by the way. The horizontal and vertical masses are the same. The effective masses are much different.
Terry9, yes, look at a picture of the Walker. Look back behind the cartridge to the intersection of the arm to the horizontal beam, the part that goes through the air bearing. At the intersection there is a clamp that joins the two. If you loosen the nuts you can twist the arm adjusting the azimuth and move it forwards and back adjusting the overhang or lack of overhang as it were. It is $120,000 but the money was not the issue, it is the design. This could be done with a stand alone arm probably for not much more than an Air Line. ET was doing it but stopped. I am not a big Walker fan. You get virtually the same isolation and performance out of an SME 30/12 with the V12 arm as you would with the Walker for less than 1/2 the price with no noisy compressors and air rushing around all over.
Terry9, yes, look at a picture of the Walker. Look back behind the cartridge to the intersection of the arm to the horizontal beam, the part that goes through the air bearing. At the intersection there is a clamp that joins the two. If you loosen the nuts you can twist the arm adjusting the azimuth and move it forwards and back adjusting the overhang or lack of overhang as it were. It is $120,000 but the money was not the issue, it is the design. This could be done with a stand alone arm probably for not much more than an Air Line. ET was doing it but stopped. I am not a big Walker fan. You get virtually the same isolation and performance out of an SME 30/12 with the V12 arm as you would with the Walker for less than 1/2 the price with no noisy compressors and air rushing around all over.