Ship Gearboxs and Speed

[WhiskeyOne]

Want some insight from folks much more experienced than I.

I have made a few large boats. 32m, 40m, 46m... All of them have medium engines, usually 2 of them, and multiple screws. One has combo screw/pumpjet. This vessel has a max speed of 35 knots. I want it to be 38-42 knots.

My issue is that with all of them, there's a common theme with the powertrain: When gears are used, the RPS and speed both drop. High gears=drop in RPS and speed. Low Gears=drop in RPS and speed. More cylinders yield no change. More engines yield no change. 5x5 engines yields no change. More propellers yield no change. Diminishing returns hit long ago but there seems to be no way around it.

From my understanding, water is relatively very dense and you need a lot of torque to move props thru it. If you have a torque output of like 800-1200 that seems to be pretty adequate. So then all you need is to find that water resistance threshold and exchange torque for RPS until you can't torque less without slowing props..

Finding that balance seems impossible tho because I can't get any data. Everything I try just makes the same result. If torque was ~600 and it drops to 400 then I change the engine to be ~800 torque, so it drops to 600. The theory being that now when I shift to higher RPS my torque will lower to what yielded a good previous speed, but only now with higher RPS, which should translate into speed! But then the same result occurs... RPS drops low and speed falls off.

Does anybody know what kind of torque a prop NEEDS? And are there some sort of mechanical force limits in this game? Have I simply hit some maximum power limit?

pls halp.

[Captain]

For props gearbox arrow should be facing the engine. Keep increasing the gear ratio until doing so reduces speed. At that point you need to increase the engine size to go faster as you are overloading the engine.

[WhiskeyOne]

Opprinnelig skrevet av Captain:

For props gearbox arrow should be facing the engine. Keep increasing the gear ratio until doing so reduces speed. At that point you need to increase the engine size to go faster as you are overloading the engine.

So with either high gear or low gear (facing away or towards) I am having the same drop in RPS. I realize water doesn't work like tires on ground, but I am surprised that there is ZERO change in the speed decrease with gears in either direction.

Also, again, as I stated:
"More cylinders yield no change. More engines yield no change. 5x5 engines yields no change. "

So you are saying this result I am getting is arbitrary and nonsensical? Because that's what I am feeling about the problem. I cannot understand this game.

[Captain]

Opprinnelig skrevet av WhiskeyOne:

Opprinnelig skrevet av Captain:

For props gearbox arrow should be facing the engine. Keep increasing the gear ratio until doing so reduces speed. At that point you need to increase the engine size to go faster as you are overloading the engine.

So with either high gear or low gear (facing away or towards) I am having the same drop in RPS. I realize water doesn't work like tires on ground, but I am surprised that there is ZERO change in the speed decrease with gears in either direction.

Also, again, as I stated:
"More cylinders yield no change. More engines yield no change. 5x5 engines yields no change. "

So you are saying this result I am getting is arbitrary and nonsensical? Because that's what I am feeling about the problem. I cannot understand this game.

Are you running the engines at the same RPS and Ratios?

If you use a 1x1 at 20 rps and a 1:3 gear ratio the prop will be going 60 RPS and for example go 60 M/S.

If you use a 3x1 at 20 rps and a 1:3 gear ratio the prop will be going 60 RPS and for example go 60 M/S.

If you use a 5x1 at 20 rps and a 1:3 gear ratio the prop will be going 60 RPS and for example go 60 M/S.

When you increase the size the engine you are increasing the "m" of F=m*a. This increases the power and therefore you can increase the gear ratio.

With a small engine the "m" is very small to to make more power you need to increase the "a" of F=m*a. Again with the goal of increasing the prop speed.

The prop is a screw for every 1 rotation it will go a set distance forward (fixed pitch). Want to go faster spin the prop faster.

It sounds like you have some design issues. Best thing to do is to post a workshop link.

[M~_22"]

Opprinnelig skrevet av WhiskeyOne:

Want some insight from folks much more experienced than I.

I have made a few large boats. 32m, 40m, 46m... All of them have medium engines, usually 2 of them, and multiple screws. One has combo screw/pumpjet. This vessel has a max speed of 35 knots. I want it to be 38-42 knots.

My issue is that with all of them, there's a common theme with the powertrain: When gears are used, the RPS and speed both drop. High gears=drop in RPS and speed. Low Gears=drop in RPS and speed. More cylinders yield no change. More engines yield no change. 5x5 engines yields no change. More propellers yield no change. Diminishing returns hit long ago but there seems to be no way around it.

From my understanding, water is relatively very dense and you need a lot of torque to move props thru it. If you have a torque output of like 800-1200 that seems to be pretty adequate. So then all you need is to find that water resistance threshold and exchange torque for RPS until you can't torque less without slowing props..

Finding that balance seems impossible tho because I can't get any data. Everything I try just makes the same result. If torque was ~600 and it drops to 400 then I change the engine to be ~800 torque, so it drops to 600. The theory being that now when I shift to higher RPS my torque will lower to what yielded a good previous speed, but only now with higher RPS, which should translate into speed! But then the same result occurs... RPS drops low and speed falls off.

Does anybody know what kind of torque a prop NEEDS? And are there some sort of mechanical force limits in this game? Have I simply hit some maximum power limit?

pls halp.

sometimes you need to add clutch because clutch is basicly the most important role of the gearbox, when i started building a tractor with only 3 cylinders but moving a gigantic tractor, it didnt really move the thing, but once you add a gearbox with a fully functional clutch, the whole things speeds up faster than you expected

[Rigben]

Engine > clutch > gearbox > propeller. If you cant get the desired speed from adjusting the forward gear ratio you need more power to turn the prop faster. If i remember torque readings are pretty unreliable and I have never used torque info myself when deciding what I do.

If you want people to actually know what you have going on you should upload it to the workshop for people to inspect. We have no context on what RPS/engine setup you are running along with vessel size and prop size.

[GrumpyOldMan]

To get the most bang for your buck you're well advised to use steam pistons. Having multiple banks (of up to 5 pistons each) piped in series is basically unparalleled in terms of power output.

There's no reason not to use steam past a certain ship size, arguably 35m+.

In terms of propulsion the fluid jets are hard to beat and can be stacked for ridiculous amounts of power, might need gearing the power source down for smaller vessels. Got a 11m patrol boat hitting 120kts with a fluid jet and 3 small prefab diesel engines.

The pitchable propellers also put out a decent amount of power, a good bit more than the fixed pitch propellers.

You can also gain a lot of speed and efficiency by lifting most of the hull above the waterline when moving, some horizontally aligned rudders will do the trick if you're not keen on going full hydrofoil.

Regarding engine power, the modular engines shouldn't be underestimated. On my 55m patrol ship I'm running 2 engines of 7cyl. 5x5 supercharged, easily hitting 110+kts at full throttle.

For AFR control I consider this to be the gold standard of controllers, allows for supercharging on the fly and no PID guesswork, all mathed out:

https://steamcommunity.com/sharedfiles/filedetails/?id=2386277437

Opprinnelig skrevet av WhiskeyOne:

From my understanding, water is relatively very dense and you need a lot of torque to move props thru it. If you have a torque output of like 800-1200 that seems to be pretty adequate. So then all you need is to find that water resistance threshold and exchange torque for RPS until you can't torque less without slowing props..

In case you're getting your torque readings from the torque sensor, it's not torque, but more akin to torque needed to turn the drivetrain. It's best to come up with your own unit to determine torque, something like rps delta multiplied by the ships mass or similar.

[Toosplash]

Yeah, I have no clue how to use gearboxes, as I just finished re-skinning and adding stuff to a ship and now she can hardly move under her own power. I've tried experimenting with gearboxes but nothing changes.

[WhiskeyOne]

Opprinnelig skrevet av Captain:

Opprinnelig skrevet av WhiskeyOne:

...I am surprised that there is ZERO change in the speed decrease with gears in either direction.

Also, again, as I stated:
"More cylinders yield no change. More engines yield no change. 5x5 engines yields no change. "

...
When you increase the size the engine you are increasing the "m" of F=m*a. This increases the power and therefore you can increase the gear ratio.

With a small engine the "m" is very small to to make more power you need to increase the "a" of F=m*a. Again with the goal of increasing the prop speed.
...
It sounds like you have some design issues. Best thing to do is to post a workshop link.

Thank you, but I still feel very misunderstood. I understand gear ratios, which is why I am so confused. But I appreciate you taking the time to type all that out. There's only the one gearbox now, as I don't see a need for complicated hi-low gear shifting in boats. I just want it to shift when the rps is high to reach a fast cruise speed and keep rps low for fuel.

I changed up the engines to add 6 more cylinders and still shifting RPS higher resulted in speed drop. The only thing that changes speed is keeping it at 1:1 with higher RPS set in the engine controller.

I will post a workshop link very soon when the vehicle is closer to being presentable and we can play with engines and gears.

[WhiskeyOne]

Opprinnelig skrevet av GrumpyOldMan:

To get the most bang for your buck you're well advised to use steam pistons. Having multiple banks (of up to 5 pistons each) piped in series is basically unparalleled in terms of power output.

There's no reason not to use steam past a certain ship size, arguably 35m+.

In terms of propulsion the fluid jets are hard to beat and can be stacked for ridiculous amounts of power, might need gearing the power source down for smaller vessels. Got a 11m patrol boat hitting 120kts with a fluid jet and 3 small prefab diesel engines.

Regarding engine power, the modular engines shouldn't be underestimated. On my 55m patrol ship I'm running 2 engines of 7cyl. 5x5 supercharged, easily hitting 110+kts at full throttle.

GREAT info! Thank you!

I feel like based on what you told me I should be getting way better performance. I am using ZE engine controller and the boat is indeed +40m with two 12 cylinder engines at max 23 RPS (I want to shift that down to <14). Draught is a bit high for stability reasons but I've seen way worse. 3 props w/ 4 pumpjets. I wanted the mix because I thought the props would be the heavy lifters and the pumpjets good for littoral. So if jets are better I switch to all jets then?

Also I did not do steam LITTERALLY because I heard so many people ♥♥♥♥ on steam. I will explore this in future builds for sure!

Will post a workshop item soon so you can all pick me apart and we can sus this problem out. Cheers o7

[WhiskeyOne]

Opprinnelig skrevet av Dr M X L:

sometimes you need to add clutch because clutch is basicly the most important role of the gearbox

unfortunately there are already more clutches than some people would consider meta, as they reduce power slightly. I have 2 on the line to toggle different propulsion types (prop/jets), plus a clutch on the engines themselves. Appreciate the input tho, for the sake of others that may come here looking for an answer. o7

[WhiskeyOne]

Opprinnelig skrevet av Rigben:

If you cant get the desired speed from adjusting the forward gear ratio you need more power to turn the prop faster.

If you want people to actually know what you have going on you should upload it to the workshop for people to inspect. We have no context on what RPS/engine setup you are running along with vessel size and prop size.

Thats the part I am not understanding.

I can't get the desired speed from adjusting gear ratios, so I add more cylinders, but I still do not get the desired speed from adjusting gear ratios. I have 24 medium cylinders now. Adding more increases speed, but shifting the prop RPS higher still results in engine RPS drop and speed decrease... I feel like I am taking crazy pills.

I will upload to workshop soon and have you pick it apart. cheers.

[Aaron]

The internal combustion engine produces more power the faster its RPS.
Thats why you lose power and speed if you decrease its leverage because more load is supressing its RPS, thus its power, thus your speed.

[WhiskeyOne]

Opprinnelig skrevet av Aaron:

The internal combustion engine produces more power the faster its RPS.
Thats why you lose power and speed if you decrease its leverage because more load is supressing its RPS, thus its power, thus your speed.

Oh i understand that all too well. That's why I am confused.

Read then part where I said adding more engines didn't change the speed drop when i geared the props to a higher RPS. Everything I did (and I did everything) resulted in slowdown when I changed gears.

[WhiskeyOne]

Update for everyone!!!

I really appreciate the attention and input. This may help others with their builds in the future.

What I was experiencing was indeed a bug. I hinted at it, but was hesitant to say so in case I was stupid. lol. After a while playing I came back to the build in question. I decided to try again to gear it up and see what happened. Lo and behold, it shifts and speed increased by 14 knots!!!

I have NO idea what happened or changed but it was happening on other crafts, so I will attempt to recreate the bug and see what does it. Post that up on the bug tracker. I have a theory it was to do with flywheels. I know I copied and pasted the engines so maybe that fixed it. re-toggled something, like it wasn't recognizing cylinders... Uncertain.

Workshop link below. It was made hastily for a MP server and is a hot mess right now. I am still in the process of cleaning up systems so it's presentable but you're welcome to check it out and tear it apart ;)

https://steamcommunity.com/sharedfiles/filedetails/?id=3319242686

[Aaron]

nice boat, if copy paste fixed it, maybe you fixed a hidden vehicle merge issue when doing it. they can be very easy to miss sometimes