+1 on that. yes it will be pricey on many levels, but it will give you power and speed and production. You decide how much that is worth. For me, time is worth a lot. The old saying from the hot rod days: 'speed costs, how fast can you afford to go?’
Ian, your feeble mind must be decent as you have figured out exactly where hydraulics has gone in the last decades: Running smaller pumps, at higher speeds, higher pressures to get the power in smaller components, lines, space, etc. etc. Farm tractors or bulldozers in the 1950's were 850 psi, with big fat cylinders to get the required forces. Now hydr excavators are 3500 to 5000 psi, and some applications push 6000 psi and above in open loop systems, not hydrostatics. Much of that is materials improvements, and much is fluid/additive improvements.
So you are correct in that a smaller pump at higher pressure can transfer the same power. (hp = flow times pressure, so increasing pressure decreases the required flow for the same power). In this case, more force at the wedge with smaller cylinder and valves and lines.
However...... the rub for a consumer is that 3000 psi is about the maximum for practical reasons. Maybe some 3400 psi per prior posts here. Common half inch two wires hoses, 37 degree flare fittings, cylinder metal tubes, cylinder cheap lip or o-ring seals, pumps, and spool valves are all generally designed about that maximum because that is where industry was for a long time. Since the largest market = largest quantity of production = lowest prices, that is the best consumer choice for the OEM splitter people. Much easier to add cylinder size than to get higher pressure components through the entire system.
Thus, assuming you are limited to about 3000 psi, this defines cylinder size for whatever force you want. Pick a speed and that defines flow and hp. Or, pick a hp and that defines maximum flows. Engineering is a game of tradeoffs, and every addition to force or speed costs money. The OEMs have settled into 5 hp, 8 hp, 12 hp because they are common engines and pumps are available. The pump people have settled into 11-13-16 gpm sizes because they match the engines well.
OK, back on topic. The 22 and 28 are in the larger frame, but both have the same small section, .465 cubic inches/revolution. (BTW, the 11 and 13 also have the same small section of .194 cir. That’s why I push the 13 gpm pump instead of the 11.) Add a large stage of .93 cir and you get 1.395 total cir for the 22 gpm version (at 3600 rpm). Add a large stage of 1.395 for total 1.86 cir and it is a 28 gpm version.
Thus, the low speed, high pressure performance and hp required will be almost the same with either version. For 2500 psi that is about 12 hp. For 3000 psi it is about 14 hp. So a 16 to 18 hp engine would be great. Larger engine, say 20 hp, does not give more psi or more speed, it just runs at slightly less then WOT to where it produces the required 12 or 14 hp. But it can do that when it is tired or out of tune and still have plenty to account for the slight extra power of the unloaded section.
Now, large section. Barnes shows performance charts for unloading settings of from 400 to 900 psi, with factory settings of 650. 900 psi is 13 hp for the 22 gpm, and 17 hp for the 28 gpm. I was emailing the Barnes AE a year back about increasing a 11 or 13 gpm pump up to about 1100 psi with shimming. It would not be blessed by Haldex at all, but was within the torque capabilities of the shaft. You could probably do it on a larger pump also, but realistically, the 900 psi matches the engine hp pretty well.
Next, do the cylinder calculations to match the flows. Maybe 28 is too much on retract speed. Remember 28 gpm into the rod side is 35 + gpm out the closed side, so the spool valve and return filter and lines all around get much bigger.
So, bottom line, if you go small engine I recommend 13 pump over the 11 pump. The next jump up is the 16 gpm. If you make the big jump in frame size and cost to the D series, you may as well go the 28 instead of the 22.
I would volunteer an excel spread sheet with all this on it but I am searching for it. Send me a pm with an email address. I can’t attach files to PM’s back. Might take a few days till I get to the old home computer.
kcj
