J_J said:
Kent, I believe that the tram pump is in the 3000 psi range, and the wheel motors also are 3000 psi motors. Most of the other hydro-stat pumps I have seen are in the 3000 psi and and greater. If I remember right, Pt told me that the relief valves on the wheel motors were set to 2750 psi. I believe that each wheel motor will see close to 3000 psi , or the relief valve setting, and that might be adjustable, when maxed out, as when trying to push against an immovable object, or the tires will spin.
I also think the tram pump is a 3000 PSI, but I'm not sure. I called Tazewell and tried to get Terry to confirm it, but I couldn't get it out of him, saying I wanted to have my system checked to make sure it's working correctly before proceeding to upgrade it. Maybe someone else would have better luck. He wanted me to remove my tram pump and send it to them, and they'd do any needed tests and inspections and repairs, if needed. He discouraged me having it tested locally, saying that basically all I could check would be the charge pump pressure, which should be about 100 PSI cold and 90 PSI hot.
As I understand it, the "working pressure" on the wheel motors in these series circuits is 1/2 that -- if they were each hooked up independently on their own circuit (i.e. parallel circuits) then they'd each be subject to the full 3000 PSI. However, as plumbed, the line to the first motor in the circuit, and consequently the inlet on the first wheel motor would be at 3000 PSI. These White RS series wheel motors that are on it now aren't even rated for 3000 PSI -- they're 1500 PSI continuous, 1750 PSI intermittent, and 2250 PSI maximum.
Meanwhile, I got the first Char-Lynn quote back for 18.2ci S series motors that I spec'd out (as described above, with high-pressure seals and low-speed valving). The quote was $387 each, with a 3-4 week lead time for the factory to build them.
While I was waiting on that quote and trying to confirm what the PSI in the circuit was, yesterday I went to a different distributor and asked for a quote on the 22.7ci S series motor (the largest one available) with the same options as the 18.2ci one above. I figured this would give me somewhat of a price comparison, and the specs on that motor are intruiging to me.
At 2gpm flow and 1500 PSI:
old 12.5ci = 2642 in lb torque, 23 RPM
S 18.2ci = 4143 in lb torque, 5 RPM
S 22.7ci = 4599 in lb torque, 11 RPM
WR 19.8ci = 3944 in lb torque, 19 RPM
at 4 gpm flow and 1500 PSI:
old 12.5ci = 2641 in lb torque, 60 RPM
S 18.2 ci = 4345 in lb torque, 35 RPM
S 22.7ci = 5200 in lb torque, 32 RPM
WR 19.8ci = 4114 in lb torque, 39 RPM
at 6 gpm flow and 1500 PSI:
old 12.5ci = 2634 in lb torque, 96 RPM
S 18.2ci = 4070 in lb torque, 60 RPM
S 22.7ci = 5117 in lb torque, 50 RPM
WR 19.8ci = 4103 in lb torque, 59 RPM
at 8 gpm flow (max) and 1500 PSI:
old 12.5ci = 2621 in lb torque, 133 RPM
S 18.2ci = 4020 in lb torque, 87 RPM
S 22.7ci = 5119 in lb torque, 74 RPM
WR 19.8ci = 4037 in lb torque, 81 RPM
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at 1000 PSI and 2gpm flow:
old 12.5ci = 1809 in lb torque, 31 RPM
S 18.2ci = 2515 in lb torque, 15 RPM
S 22.7ci = 3447 in lb torque, 15 RPM
WR 19.8ci = 2711 in lb torque, 20 RPM
at 1000 PSI and 4 gpm flow:
old 12.5ci = 1798 in lb torque, 68 RPM
S 18.2ci = 2897 in lb torque, 40 RPM
S 22.7ci = 3613 in lb torque, 38 RPM
WR 19.8ci = 2813 in lb torque, 43 RPM
at 1000 PSI and 6 gpm flow:
old 12.5ci = 1721 in lb torque, 108 RPM
S 18.2ci = 2694 in lb torque, 67 RPM
S 22.7ci = 3494 in lb torque, 58 RPM
WR 19.8ci = 2774 in lb torque, 65 RPM
at 1000 PSI and 8 gpm flow:
old 12.5ci = 1697 in lb torque, 144 RPM
S 18.2ci = 2516 in lb torque, 94 RPM
S 22.7ci = 3515 in lb torque, 78 RPM
WR 19.8ci = 2701 in lb torque, 88 RPM
The 22.7ci S series is only rated at 1300 continuous and 1500 PSI intermittent, versus 1500 PSI continuous and 1800 PSI intermittent for the 18.2ci. If I could confirm that the tram pump was operating at 2600 PSI or less, I'd be real tempted to go with the largest motor. Note that at 2 GPM it is faster than the smaller 18.2ci one at 1500 PSI and the same speed at 1000 PSI. At 4 GPM they're at almost the same speed -- it's only at the higher flows of 6 GPM and 8 GPM that it is significantly slower. Meanwhile, the largest motor is producing much more torque -- over 1000 in lbs more than the 19.2ci version in some ranges... it literally doubles the torque produced by my stock wheel motors. By my calculations, these would push the PT at about 5.5 MPH at full throttle, full treadle -- assuming 80 RPM wheel motor speed, based on 8 GPM flow and PSI of 600 or less, where it is still producing more torque than my stock wheel motors. If that speed proved to be too slow, moving up from 23" to 26" tires would speed it up to about 6.2 MPH -- again, assuming 80 RPM and 8 GPM. In comparison, the smaller 18.2 ci S series should push the PT at nearly 7 MPH (6.84) MPH, assuming 100 RPM and 8 GPM flow.
But, since the larger wheel motors are only rated for 1300 PSI continuous, I'm reluctant to use them since I can't confirm the tram pump's PSI output. Similarly, the 19.8ci White WR series motors outperforms the 18.2ci Char-Lynn S series motor at 1000 PSI in most flow ranges, but not at higher pressures. That White motor, though, is rated at only intermittent use at 2 GPM and 1500 PSI -- which seems to me where you want to be able to use the full pressure potential (i.e. torque) of the wheel motor. I will wait to see the final Char-Lynn price quote for the largest motors, though, before I pull the trigger -- even though the quoted $387 price seems fair enough for a special order item (with options), when compared to johari's $380 price. Should this other distributor come back with a significantly lower price for the largest motor (with the same options) then I'll have them quote me the 18.2ci ones...
Meanwhile, I have to wonder how the low speed valving option I specified will improve the performance of the 18.2 ci motor at lower GPM rates, such as 2 GPM especially. It's hard to understand how the "standard" larger 22.7ci motor can both turn faster and generate far more torque at those low flows. This option could even impact RPMs at the higher GPM rates if it does improve the efficiency of the motors at under 200 RPM, as claimed...
) that the current system -- with two series circuits -- is likely limited by relief valves to 1500 PSI total. Without that pressure drop from series circuits, the system would go to 3000 PSI, theoretically, but that is limited by the relief valves. That was the foundation of the whole "Stray mod" concept. But, these White wheel motors couldn't stand those types of pressures.