Stomp grate question

[PSG-1]

How close together can you space the tines of the intake grate without blocking flow and affecting performance?

Right now I'm in the process of re-building my grate, using 1/4" X 3/4" stainless flat bar, and they are currently laid out to be spaced with 1/4" between them. I have heard of people running them as close together as 3/8". Just hoping the 1/4" isn't too close.

 

[CedarRiverScooter]

I don't know the answer, but I bet the cross section shape of the tines is really important. Maybe a tear drop shape?

 

[PSG-1]

The existing tines I'm using have been ground with a knife edge on the bottom side, and a round radius on the top side. I was previously running with 6 tines, spaced about 3/4" apart, and it didn't affect performance. I'm adding 3 more, and have shaped them to the same pattern as the others.

 

[RiverBottomOutdoors]

When I beveled my grates on my outboard I found that junk wedged in them more.

 

[PSG-1]

Yeah, I was doing some reading on the shape of the tines after posting this. According to what I've read, the backside should have more bevel, the front should be slightly round. Guess I need to re-shape them before putting it all together. A little re-shaping won't hurt to reduce the weight, that's for sure. But I'm still wondering about the 1/4" spacing causing the pump to starve and cavitate.

 

[CedarRiverScooter]

If you are building a new one, don't have much to lose by trying the 1/4 spacing (other than your time). Let us know how it works out. I might make one like this too, someday.

 

[Ranchero50]

I would be more concerned about the pressure drop behind the grates. If the area taken by the grate is much smaller than the area of the port behind the grate I think the water would be more susceptible to cavitate, especially if you are close to pump area (pie x R2).

However if your grate opening area is much larger than the pump face area you should not have a restriction at the grate. I think that's why mine works pretty well. I used a sport jet grate and the area between the grates is much larger than the pump inlet area. Basically the S/J grate is slightly shorter but 3x the width of the Doo grate. You do not want any venturi effect (pressure drop) through the grate (contributes to cavitation) and a larger grate area will allow you to maintain performance with a partial blockage.

 

[Capt1972]

I would be more concerned about the pressure drop behind the grates. If the area taken by the grate is much smaller than the area of the port behind the grate I think the water would be more susceptible to cavitate, especially if you are close to pump area (pie x R2).

However if your grate opening area is much larger than the pump face area you should not have a restriction at the grate. I think that's why mine works pretty well. I used a sport jet grate and the area between the grates is much larger than the pump inlet area. Basically the S/J grate is slightly shorter but 3x the width of the Doo grate. You do not want any venturi effect (pressure drop) through the grate (contributes to cavitation) and a larger grate area will allow you to maintain performance with a partial blockage.

summed up: lack of suction pressure

 

[PSG-1]

I was previously running with 6 bars, and the plan was to add 3 more. I'm really hoping those extra 3 bars don't affect it much. The main objective is to keep oyster shells or rocks out of the pump and the opening between the existing 6 bars is just too wide, being roughly 3/4- 1" inch spacing. Large gravel can easily pass through, and I don't like that. I see the potential for a jammed rock in the stator, and a long drift back to a landing. I've been lucky thus far, but would feel a lot better with a grate that won't let stuff get in there that's going to jam the pump.

 

[Capt1972]

has anyone tried rabbit hutch wire or something similar?

 

[PSG-1]

Seems like that would be weak, and could break if it impacts something, allowing it to pass through. Also, the problem arises in how to modify/convert that into a stomp grate. The longitudinal bars swing up and down and allows stuff to clear. Rabbit hutch wire seems like it would be impossible to clear weeds from, due to its design.

 

[CedarRiverScooter]

What if the grate was concave? It would provide more open surface area.

Just a wild thought, I know it's not practical . . . -10 F here, not going outside all day, onset of cabin fever!