VDO Sumlog problems

[VicS]

The log is not working. Although I have not looked at the lower unit yet it seems that it is jammed down there somewhere although I am told it appears ok from a visual inspection from outside.

I know we can get a new inner cable or even the whole cable assembly if needed but not the impeller.
What is involved in removing and replacing the inner cable?
How is the impeller attached to it?

Can any body offer any advice please.

 

[Norman_E]

From your description it sounds as if you are talking about a mechanical log instrument with a speedometer cable type of drive, in which case it will be quite different from mine. If however yours is the electronic type the following might help.

My instruments are VDO Siemens make, and I think that the log impeller is the same. It can be easily removed by unscrewing a cap, pulling it out and quickly inserting the blanking plug. Make sure your log unit is facing the correct way. On mine there is a stainless wire loop at the top which is asymmetric. Viewed sideways it has a slightly pointed aspect, and the point should face forwards. Sometimes the log fails to register when I leave the mooring, and I find that if I slacken the screw cap, twist the log from side to side and realign it correctly the log will come to life. My guess is that the bearing of the little paddle wheel gums up a bit at rest, and a few quick twists of the unit are needed to free it up. Funny thing is that if I remove it, it always feels quite free spinning.

 

[VicS]

[ QUOTE ]
From your description it sounds as if you are talking about a mechanical log instrument with a speedometer cable type of drive

[/ QUOTE ] Yes that's right. Sorry I should have made that clearer

 

[DaveS]

This is going back a bit, but I had a Wasp mechanical log on my first boat which sounds similar: working on the mechanical speedometer cable principle: rotating inner wire inside static sheath. Mine was very fussy about the cable's bending radius: slightly too tight and it would stop dead. Could yours have got moved a little, say by something pressing on it?

I also seem to remember that after a couple of years the bottom end of my cable started to corrode, and I tried to keep it going by, contrary to the manufacturer's instructions, running oil down the inside; the theory being that with the instrument head above the water line the oil pressure should be greater than the water pressure, and any small leak would result in oil seeping out rather than the sea seeping in. This worked, sort of, but the extra friction meant that it took a higher initial water speed to make it go.

I can't quite remember how the inner cable was fastened in place. There was a square section bit at the bottom (?) end which just slid in to a female square, but since the cable could be cut to length the other end must have had some sort of clamping arrangement. Maybe not much help - sorry.

 

[DavidGrieves]

Hi

You can get spares here http://www.furneauxriddall.com/shop/acatalog/Inner_cables.html

I replaced an inner cable a while ago. I can't remember how the impellor was attached to the spindle, but I don't think you have to remove it to replace the inner cable. I think it went like this...
Buy a cable over length.
Remove the old inner cable.
New cable has one end squared off, thread this end through outer cable, until it sticks out of the impellor (is boat out of water?).
There is an end fitting that has to be crimped on to the instrument end of cable, kit comes with the tool to crimp and instructions.
The crimping tool is just a flat piece of metal with a slot in the centre, once you have worked out the length required you remove inner cable, place cable and end fitting in the tool and whack it with a hammer.
Does that help?

 

[DavidTocher]

I have exactly the same VDO mechanical log on my Galion 22. You must have access to the impellor because the square end of the inner drive cable is a tightish push fit into a square hole in the impellor. If the old cable has broken then
the only way to get the lower section out is from the impellor end. I replaced my broken inner without any problem; pulling the top section out at the display head and the bottom section from under the hull. I removed the impellor from the hull (3 or 4 bolts) and pull out the old and poked the new inner into place. A very easy job!

 

[Talbot]

Me too, and agree about needing to have access to the impellor on the outside in order to retrieve the broken cable. I normally use a small hole puch to drive it back inside the boat. With mine I need to shorten the cable before attaching it to the instrument , but that is a quick hacksaw job, and I then rapid araldite the top bit together (seems to work better than the recomended crimping)

The replacement inner cables are easily and cheaply obtainable from a VDO stockist (Furneaux Riddell in Portsmouth).

 

[Bodach na mara]

Lots of correct advice here, especially the bit about having access to the impeller. I would not try to renew the cable with the boat in the water. On one occasion I had to dismantle the impeller to remove some nylon fishing line as it was not only a broken cable that was stopping it working.

 

[VicS]

[ QUOTE ]
On one occasion I had to dismantle the impeller to remove some nylon fishing line

[/ QUOTE ] Can you elaborate on what is involed to do that. In our case the cable is not broken as far as I can tell. At least it cannot be tuned if it is disconnected at the top so I am assuming it is something seizing things up down below such as some fishing line. I have not had a chance to look yet for myself but I am told there is nothing visible. I was afraid the underwater unit may have been damaged when the boat was craned in but it seems that is not the case. All will be revealed when the boat is craned out again but I am trying to get an understanding of what might be involved to sort it out. I am wondering if it is possible to do very much without sacrificing the cable.

 

[Bodach na mara]

To dismantle the impeller unit, you must first clean off all the old antifouling from the rotating bit. Once you have done that, look carefully at the impeller and you should see that there are flats at the forward end. These are only about 1mm thick and it is these that you must get a grip of. I used the parallel jaws of a vernier calliper (brutal, but all that I had available) and held the flats while turning the propeller bit. Unfortunately, I can't remember which way i.e. is it a left-hand thread? It probably turns the opposite way that it would normally turn when going forward through the water. After you have unscrewed the nylon impeller, you can get at the spindle, which is held on by a nut, but you may be able to remove obstructing material without doing this.

One final point if you do need to fit a new cable. A previous post refers to placing a crimping tool over the cable end and "giving it a whack." Do this and you will probably break off the square end of the plastic drive that you are trying to fix on! I had to call VDO and a nice chap at the other end told me that nearly everyone does that. He went on to say that they should put a spare end and tool in every kit to save trouble sending them out, which he did without charge. He advised either hitting it VERY carefully, or crushing it in a vice, again carefully. I was also advised by another seasoned bodger to complete the job by putting a dimple in with a centre punch, again using great care.

 

[VicS]

Thanks for all the advice. I will take a look at it when the boat is craned out