need hydraulic helm help

[old377guy]

As I get ready to rig full hydraulic steering for my 38' Scarab I'm finding that I need more info on the Char Lynn hydraulic helms. I understand that they are the preferred units but there is an absolute maze of model numbers out there. At one point I thought I needed a 211-1001, but that number is not right and there seems to be a newer? models that have superceded it. I want to shop for a unit and would really like to know what all the numbers and codes mean. Do I need a 4.5 cu. in, 6 cu. in..What configuration will work for me. I;m willing to be creative improvising a steering wheel shaft that will connect to whatever unit. I also see a huge variety of prices from $150 to $600 and it seems that these units should be common as many seem to fit forklifts, dune buggies, off-road machines, tractors etc. Any insight is appreciated. - Jeff

[gcarter]

Maybe this will help.....
If you look at the document, on page 2, there's an illustration showing the standard linear dimensions. Dimension "C" is the length of the gerotor pump that determines the displacement of one revolution of the helm.
Clear, right?
On page three is a chart showing the most popular geroter pumps and its displacement listed in metric and inches.
So what you do, if you have a dual cylinder setup, is find the displacement of one of your cylinders, then the displacement of the back side of the cylinder (the back side has a rod, so you have to subtract the displacemant of the rod from the cylinder displacement). Then add the two displacements together so you know how much fluid is being used to go from lock to lock. If you want three turns from L to L, divide the total displacemant by three, or however many turns you want.
Then all you have to do is pick the geroter length that coincides with the one revolution displacement you need.

Simple!:)

There're newer helms around but there's still millions of these around.
You will want a 211- open center helm.
Also there're a few more possible numbers available, but this list covers most of them.

[old377guy]

thanks g, this is helpful - Jeff

[old377guy]

one more thing, is there a reason that I couldn't use a unit that was from another type of application? (off-road vehicle, forklift, etc.) - thanks - Jeff

[gcarter]

You could if it was right in every aspect.
Assume you found a 211-XXXX, and the correct port size, etc....
Any good Char-Lynn repair shop could set it up for you the way you want it.
The more you want the donor helm changed, the more it would cost.
A new helm like what you want is $500.00 +/- just to give you a feel for it.
There're many, many options. The basic helm can be configured for many applications. There're pipe thread, and AN port options. Anyone that hates leaks doesn't want pipe threads. There're choices for different types of steering columns. There's a butt ugly column that's pretty common and has to be camoflaged in some way.
Another option is a splined recess and Latham makes a beautiful polished SST column 3" and 6" long for that option. These're about $500.00 new but I've seen many for about $150.00, like the one I got on ebay.

http://www.seriousoffshore.com/forums/attachment.php?attachmentid=59306&stc=1&d=1270597107

http://www.seriousoffshore.com/forums/attachment.php?attachmentid=59307&stc=1&d=1270597107

And this is my helm, a 211-1010, which has the recessed splined input, AN ports and a gerotor that's .88" long, or 9.7 Cu. in. (160 cc) to feed some monster Hynautic K-5 cylinders w/25 cu. in. displacement. This is a used helm set up for me by a friend in the business.

http://www.seriousoffshore.com/forums/attachment.php?attachmentid=59308&stc=1&d=1270597107

So shopping around is a good idea, but ya gotta know what you want when you start looking.

[gcarter]

If you find on of the Latham columns, make sure you get the trim ring, studs, acorn nuts, and trim gasket. Latham charges a fortune for each and every part of it.

[old377guy]

man this is invaluable info g, I just found a 211-1010 unit for $125. I'll look at it in a few days. The guy has many of these setting around. I'll bear in mind what you said about the transition pieces from the interior spline to a hub flange for my steering wheel. I'll probably have my shop fabricate something. Thanks again for all of the help.