At speed, is T&T system under a constant load?

[KeyWestSkipper]

When underway and not being adjusted, is the T&T system absorbing any of the forward force of the motor? Or is it somehow isolated from those forces and perhaps only under a load when the operator makes trim adjustments and moves the rams. Hope this question makes sense.

 

[dingbat]

Re: At speed, is T&T system under a constant load?

There is no isolation. The trim absorbs the full force, which by the way in the world of hydraulics, isn't squat.

 

[KeyWestSkipper]

Re: At speed, is T&T system under a constant load?

There is no isolation. The trim absorbs the full force, which by the way in the world of hydraulics, isn't squat.

Thanks for the reply and I'm glad you added that about the hydraulics - exactly what I was wondering about.

 

[RRitt]

Re: At speed, is T&T system under a constant load?

The force of the motor pushes down on the piston.
That force is converted into PSI where PSI=thrust/sq inches.
The PSI is transmitted back to the pump through the fluid.
The fluid is prevented from backward movement by the check valve
A shuttle piston opens the check valve when the trim motor is running
A bypass valve sets the maximum forward PSI
Most pumps do not have a bypass vavle for backpressure.
If the engine is too powerful backpressure can crack the pump or cylinder.

 

[dingbat]

Re: At speed, is T&T system under a constant load?

The force of the motor pushes down on the piston.
That force is converted into PSI where PSI=thrust/sq inches.
The PSI is transmitted back to the pump through the fluid.
The fluid is prevented from backward movement by the check valve
A shuttle piston opens the check valve when the trim motor is running
A bypass valve sets the maximum forward PSI
Most pumps do not have a bypass vavle for backpressure.
If the engine is too powerful backpressure can crack the pump or cylinder.

I designed hydraulic drive and control systems for 15 years. You have me scratching my head with this response.

 

[kenmyfam]

Re: At speed, is T&T system under a constant load?

There is no isolation. The trim absorbs the full force, which by the way in the world of hydraulics, isn't squat.

I'm with Dingbat on this one.

 

[RRitt]

Re: At speed, is T&T system under a constant load?

I designed hydraulic drive and control systems for 15 years. You have me scratching my head with this response.

just following the force of the prop back through the system and trying to put it in the simplest possible terms.

prop pushes engine down on piston - piston compresses fluid - pressure goes back to pump - check valves stop gears from spinning backwards and motor drifting down under load - if engine is too far in excess of designed capability I have seen check valves burst open and in extreme cases cylinders crack. For example some outboard engines have the ram attached 3" from pivot with 24" or more from pivot to prop. If you hook up a 150HP engine with a 8-1 leverage advantage on a single ram system it can create some pretty substantial pressure.

By the way - if you design these things then why don't they just make a trim system using a design modeled after disc brake calipers? It would be so much cheaper to build and easier to service. So what if it doesn't work when you turn the boat upside down? Just say in the owners manual not to drive your boat upside down.