Subsea cable end

[Hitch]

What a nightmare job!
Got the initial one done, but now suggested lots of modification for the other 9.
Had problem after problem with it. I thought the idea of cad was to be able to spot problems with things hitting etc. Some more measurements on the drawings would have been usefull aswell

The lug arragement between the inner and outer cage was the major problem, if i had have done it as per drawing, it never would have gone together, the flange on the end would have hit the lugs

I can't take credit for the machined bits, that was done by a firm across the road.

 

[wyn]

That's a fair bit of kit. Does it join two cables or is it used to drag it along ?

Do you get that a lot, Hitch....Drawings that are impossible/ difficult to actually make.

 

[Hitch]

I think its for joining.

Tend to get a good few things that have been made very hard to fabricate by the designer.

 

[weldingscotty803]

how long to make hitch?
suppose yiou will get quicker after youve made a few.
but you have to do all them changes o ooooo

 

[runnach]

Neat bit o fabbing and welding Hitch, must have been a mare making sure plates with holes lined up and within tolerance!!

 

[weldingscotty803]

what were the tolerence like +/- 2mm for a guess

 

[Barney1973]

Looks like a quality bit of Fabrication,must have been a right headache to build!

 

[Welderpaul]

Nice. How did you align the channels and machined plates that are in the centre of the assembly?

 

[Hitch]

0.25mm on the drawings.

The lugs on the channels sit inside machined blocks, the blocks welded to the round bar.
Bit of a job on to get them all lined up, the block had a 21mm slot in it, bar the lugs are from measured 20.3.... leaving me 0.7 mm to play with between 4 lugs

The welding on of the blocks bent the 60mm bar slightly and they sprung in 10mm+ after the jig was removed. Luckily, if you get angry with it you can move the ends of the bars 10mm to spring them into the collars on the mating frame.

Timewise, very difficult to say really. I guess about a weeks work, sorting out the problems, modifying, redoing, modifying, redoing....making tooling, jigs etc.

Rest, if its made how i suggest, about 2.5 days i reckon.

 

[Hitch]

Nice. How did you align the channels and machined plates that are in the centre of the assembly?

If they bolt in, that good enough for me.

Had to use a podger on 1 hole, not bad.

 

[StickNtig]

what were the tolerence like +/- 2mm for a guess

2 mil!!??


i made some lightning conductors for an offshore windfarm and the hole tolerance was stated as 0.0001mm max

Tolerance=room for error

 

[runnach]

2 mil!!?? tolerance was stated as 0.0001mm max

Drive a tank through that tolerance

 

[snowcat]

nice work hitch,

0.0001 blimmey hope they produced an exotic for that, ground flatstock 1A can be under by - 0.0127mm

 

[weldingscotty803]

2 mil!!??


i made some lightning conductors for an offshore windfarm and the hole tolerance was stated as 0.0001mm max

Tolerance=room for error

thanks for that, i know what tolerences are. my digital verniers only got to 0.001mm. they arent the cheap ones either, 130 quid i think they set me back.
how can you get within those tolerences? was it lathe work? reamer jobbie?

0.25 is quite tight. we work to 2mm+/- on the frames i make. but there for landfill.
most of us lads and lasses on here are diyers and cant imagine working to tolerences like the ones stated above. worst thing i had to contend with was a pin at work which had to be +/- 0.02 of a mil. i thought that was close. no digital readout either, all manual on a lathe

 

[malcolm]

I've spotted drawings in the past where the person who did the drawing clearly had no clue about tolerances. 1/10 thousandths of a millimetre is well into polishing territory is it not? Edit: I see it's possible with grinding - see handy pdf on typical tolerance

I hope the client was charged suitably, and I'd expect client quality control was carried out in the same temperature controlled room as the work before the structure was moved. What other precautions did you have to take to achieve that? A dead digital measuring stick with a transparent label showing the correct dimensions would have been my approach.

Very neat looking fabrication Hitch.

 

[weldingscotty803]

I've spotted drawings in the past where the person who did the drawing clearly had no clue about tolerances. 1/10 thousandths of a millimetre is well into polishing territory is it not?
I hope the client was charged suitably, and I'd expect client quality control was carried out in the same temperature controlled room as the work before the structure was moved. What other precautions did you have to take to achieve that? A dead digital measuring stick with a transparent label showing the correct dimensions would have been my approach.

Very neat looking fabrication Hitch.

thats what i thought. but he stated they were holes, so a good reamer would do the job with those wouldnt it?

what were the dimensions of the cable things hitch. length width height and what steel was used.
did you get ground flat stock?

 

[Robotstar5]

What sort of measuring equipment was used as it has to be more accurate by a factor of so many to the tolerances specified?

 

[Hitch]

Its all plain old steel, plate, black flats and round bar. Grade wise, s275 for the plate, flats and rounds, not sure, s235 perhaps, not sure, i only put it together!

The only ground stock was what the milled blocks were cut from, then machined back. They have taken onboard my advice, and no longer using them now.

 

[Hitch]

Well, they are just about finished now. Been dye-pen testing and load testing them yesterday/today.

Spent a bit of time on other jobs in between last few weeks.


8tons lift each way.
Load sensor between crane hook and load.
Nearly 10tons of plate, used to keep it down.

 

[Welderpaul]

Good photographs. Crane driver in the usual position then!

Appear to be much deflection/disortion when they were loaded?