BobRip said:
SInce the geroler has more low end torque, eqaul displacement motors as compares to gerotor should have more low end torque. So would it be OK to use geroler motors of the same displacement and you would have the torque and the speed. Is my assumption here valid?
Bob,
Neither the Char-Lynn S series geroler nor the White WR series geroter come in exactly the same size (12.5 ci) as the White RS series geroter that I have on there now. However, there's sizes that are fairly close. Since I have the catalogs on hand and the comparison charts set up, here's what they look like for the size closest to stock, yet larger -- I can't see you wanting to lose torque and gain speed by going smaller. I can only do a direct comparison at the 1000 PSI level, since the charts use different increments. But, it should give you some idea:
at 1000 PSI and 2gpm flow:
old RS 12.5ci = 1809 in lb torque, 31 RPM
S 13.7 ci = 1884 in lb torque, 23 RPM
WR 14.4 ci = 1979 in lb torque, 26 RPM
at 1000 PSI and 4 gpm flow:
old RS 12.5ci = 1798 in lb torque, 68 RPM
S 13.7 ci = 2103 in lb torque, 57 RPM
WR 14.4 ci = 2062 in lb torque, 56 RPM
at 1000 PSI and 6 gpm flow:
old RS 12.5ci = 1721 in lb torque, 108 RPM
S 13.7 ci = 2079 in lb torque, 91 RPM
WR 14.4 ci = 2010 in lb torque, 88 RPM
at 1000 PSI and 8 gpm flow:
old RS 12.5ci = 1697 in lb torque, 144 RPM
S 13.7 ci = 2131 in lb torque, 125 RPM
WR 14.4 ci = 1952 in lb torque, 115 RPM
At 2 GPM flows, these Charl-Lynn S series geroler motors don't seem to perform quite as well, and don't produce the RPMs of a geroter, though they produce good torque. But at 4 GPM (half-treadle)and above, they outperform them in producing both torque and RPM. At 6 GPM and higher, they produce more torque than the larger WR geroter motors, in addition to producing more RPM (which would be expected).
Here's the S series performance at higher PSI ratings. (Too bad the manufacturers don't provide their data in the same increments to facilitate comparisons -- but I suspect that is interntional.)
at 2gpm flow:
old RS 12.5ci at 1500 PSI = 2642 in lb torque, 23 RPM
S 13.7 ci at 1400 PSI = 2787 in lb torque, 16 RPM
WR 14.4 ci at 1500 PSI = 2894 in lb torque, 24 RPM
at 4 gpm flow:
old RS 12.5ci at 1500 PSI = 2641 in lb torque, 60 RPM
S 13.7 ci at 1400 PSI = 2992 in lb torque, 49 RPM
WR 14.4 ci at 1500 PSI= 3063 in lb torque, 50 RPM
at 6 gpm flow:
old RS 12.5ci at 1500 PSI = 2634 in lb torque, 96 RPM
S 13.7 ci at 1400 PSI = 2923 in lb torque, 83 RPM
WR 14.4 ci at 1500 PSI = 3028 in lb torque, 81 RPM
at 8 gpm flow:
old RS 12.5ci at 1500 PSI = 2621 in lb torque, 133 RPM
S 13.7 ci at 1400 PSI = 3017 in lb torque, 116 RPM
WR 14.4 ci at 1500 PSI = 2973 in lb torque, 111 RPM
While these are not direct comparisons (1400 PSI for the S series geroler vs 1500 PSI for the geroters), they should give you a sense of the difference performance levels and curves. Again, at 2 GPM flow the geroler doesn't perform as well as the geroters in producing RPM, but it produces good torque at a lower PSI. The larger White WR moter actually produces more RPM at 2 GPM than the smaller S-series geroler. At 4 GPM and above it's about the same as the larger WR geroter in both RPM and torque, though it's at 100 PSI less. At 8 GPM it is actually producing more RPM (expected, because of smaller displacement) but also more torque than the larger geroter, despite running at 100 PSI less.
Again it seems that the geroler is not as efficient at 2 GPM flow (at least without the Low Speed Valving option) in producing RPM, but it still produces good torque. At 4 GPM and above, it clearly outperforms the gyroters in both torque and RPM. It outperforms the stock, smaller 12.5ci RS series gyroters in torque at all flows, with 100 PSI less, yet it obviously cannot match the RPMs.
What I don't know is how the Low Speed Valving option that I specified will impact these low flow numbers. I assume it will help them somewhat, since it optimizes the motor for operation under 200 RPM, but I can't quantify that...
It seems the 13.7ci S series geroler would produce a noticeable improvement in torque at all speed and flow ranges, yet the difference is most noticeable at half-treadle and above, yielding higher GPM flows. Too bad the S-series doesn't come in a size between the 13.7 ci and 18.2 ci -- something along the line of a 15.3ci or 15.9 ci. Those sizes would yield a siginificant improvement in torque that would not require sacrificing as much top end speed as the large 18.2 ci ones does. Yet, they'd be an easier conversion, done by enlarging the hole in the body as johari has done.
Note that the Char-Lynn W series gyroler comes in a 15.3 ci displacement, with all the innovations of the new S series, but it is a "short, stubby" motor with 1.25" tapered shafts that would require making new wheel boxes and replacing the wheel hubs. The White geroter motors come in both a 15.5 ci for the RS series (the series mine has now, with 1" shafts) and 15.9 ci for the "short, stubby" CE series with 1.25" shafts. I think the newer PT-425s have either the 15.9 ci White CE geroter (most likely) or the 15.3 ci W series Char-Lynn. Either of these would yield the "about 40% increase in torque" that we hear, but they'd also require the new style, larger "wheel boxes" to mount them.
If someone wanted to build the new style wheel boxes and buy 1.25" wheel hubs, the Char-Lynn 15.3 ci W-series geroler with parking brakes on
Surplus Center for $329.95 would be a GREAT conversion...
Hope this has been of some value...
