825 ml in Robbe u47

[joeangi]

I was just wondering if anyone had fit an 825 ml Engle tank in the Robbe u47. I know that the 750 fits...but am thinking of shoehorning in the 825.

[safrole]

The 750ml is already a

The 750ml is already a shoehorn, IMO. I was not even aware of an 825. Maybe they'll be like models of BMW. You know, an 825TAES, black with silver trim.

I am happy with my 750ml waterline. I'm also happy with my 12v setup. In fact, I'm just plain happy with everything, except that I should have reinforced the hull seam just under the front planes and glued on the aft hull section more thoroughly. To make the leap to a truly scale waterline, you would need (I am told) to go to a full liter or more.

Check my sig for the website, in case you haven't seen the mods I made in my Robbe.

Chuck Anderson has also built a bunch of these and has some upgrades for sale. They are definitely worth checking out.

[joeangi]

Thanks for the reply....I have

Thanks for the reply....I have the 750 and would like the additional water line height of an 825. It is a total of 40mm longer....its only 4cm. I just don't know if I am ready to re-engineer again...

Joe

[safrole]

Hey how many amp hours

Hey how many amp hours do you have on board and what kind of run time do you get? Also do you have shaft seals?

People malign the Engel tank as an electric hog and I just don't see it as a problem, personally. I'd like to hear your take on it.

[tsenecal]

Joeangi,

is the cylinder 4cm longer?

[color=#000000]Joeangi,

is the cylinder 4cm longer? if so then the true length delta is really 8cm, for both the cylinder and the rod...

having also built a 750ml unit into my u47, and dealing with all the issues due to the way water fills the tank, ie, the FACT that the center of gravity shifts 4" while the cylinder is filling, and the fact that 750ml is about 95% of what you really need, I think a better plan is to take two of the 500ml tanks and see if you can somehow squeeze them into the sub. one as far forward as possible, and one as far aft as possible, and have them pointing in opposite directions. Maybe even cut them down a little bit and make them each 425ml units.

I have no idea how this would be done, but stranger things have been accomplished.

In my mind the perfect retro-fit kit for a piston tank u-47 would include the following]

[thierryc]

I am using a much

[color=#000000]I am using a much simpler system]

[joeangi]

The idea of 2 500ml

[color=#000000]The idea of 2 500ml tanks sound like a electrical nightmare on top of an engineering one. I doubt that the results would be worth the "cost"

I am currently running 2 3000mah 5 cell packs wired in parallel, so 6v/6ah. I have not had an issue with run time...even towing weeds it lasted for more time than I needed. I am running speed 400's geared 3]

[joeangi]

P.S. I am sure that

P.S. I am sure that the tank is a "amp-hog" but it has really not turned out to be an issue. I would love to run a smaller motor on it, as I feel the stock motor is really overkill due to the amount it is geared down.

Full time of ballast blow for the 825 ml tank is 18 seconds....so it is not like it is running for that long, even with multiple dives.

[safrole]

My internal pressure is pretty

My internal pressure is pretty high as well. I have shaft seals and if I don't keep them greased they can fart a little at full flood. If I keep a little grease on the insides I have no trouble at all. A shaft seal retrofit would be an involved project, but it sounds like you're ready for major mods anyway.

[bigdave]

Just for reference, my best

Just for reference, my best friend DonO runs Engel tanks in all his subs. He has replaced all the 540 motors with 400 motors. It was a very easy conversion to do. They use a lot less power, and the tanks work great. Just thought I would mention it. Dave.

[tsenecal]

I tried to replace my

I tried to replace my 500 size motor on the tank with a 400, but couldn't find any one willing to sell me the gear that goes on the motor, so that I knew I wouldn't be stripping any teeth on the gears on the tank.... where did DonO find the gears?

[joeangi]

Thanks for all the replies

Thanks for all the replies guys...I am going to look at that 400 motor selection....that would also give more clearance for the tank.

Well no says that you can't do it...I guess that means, out with the saw again.....

Shaft seals are definite with the re-build.

I have an e-mail into Greg at Engle for a quote on the new tank.....

I will keep you posted, as i know they are closed for the month
Joe