Doxford timing valves

Steve Hodges
3rd May 2009, 15:45
Mention of setting Doxford timing valves in the thread on indicator cards has re-awakened an old "niggle" that has been lurking at the back of my mind for the last thirty-odd years - perhaps some of you experienced Doxford fanatics can pt it to rest for me.
I only sailed one trip on a Doxford, it was a 1961-vintage six cylinder with scavenge air pumps, I think it was an LB model. I was 3/E, with a Chief's steam ticket doing motor time, so I took a bit of stick from the "motor men " on board . I was responsible for the engine fuel system, and was asked to even-up the firing on each cylinder because the engine was a bit lumpy at low revs when manoeuvring. I referred to the Doxford manual, read up the procedure for setting the fuel timing valves, and next time we were at anchor I had a go. The results were awful, the engine was so unbalanced that it was a pig to start and would not run at dead slow. When we berthed I tried again, with no real improvement, although I was convinced I was doing things correctly "by the book"After a lot of head-scratching, and a lot of good-natured abuse from the "motor men" I came to the conclusion that the instructions in the book could not work practically, because they involved measuring a gap with feeler gauges against a spring loaded piston. I worked out my own method of setting them, which was slower because you had to turn each "leg" one complete revolution, and by this method I got the engine balanced again, although running a little fast for manoeuvring. Correct running speed was then achieved by adjusting each "leg" in turn by exactly the same amount, which kept the engine in balance. When I had achieved that, I left the timing valves well alone for the rest of my time aboard!
Does this ring a bell with any of you Doxford men? Or was I just being dense? Or was maybe the manual written in Geordie and incomprehensible to a southerner like me? It may be some thirty years ago, and the detail a little hazy, but it [U]still[U] irritates me - I think it dented my professional pride ( such as it was!).

Ian J. Huckin
3rd May 2009, 18:39
I understand where you are coming from Steve, and although all my LB Doxford time was as Eng. App. I think I picked up that an engine should be balanced at MCR, that is to say, firing pressures should be balanced at your normal FSS RPM. Economy revs, and reduced revs for heavy weather and manouvring speeds do not count.

So saying, set the engine up on static timing then fine tune it at normal FSS RPM. If your fuel valves are in order, be they mechanically operated (still on Doxford here) or pressure operated then the performance should mostly stay in line pro-rata with the reduction in engine speeds.

Often enough a poorly starting engine can be traced back to less than efficient air start valves or even incorrect air start distributor timing. Especially noticable the less cylinders you have.

Doxfords have to be the best learning experience for a marine engineer. Apart from the above there was fuel pump strut setting and that whacky reciprocating governor, there was no end of feedback the engine would give you once you worked on anything. Hence the rule "one adjustment at a time" and then recognize the feedback.

Although I was not a Steam Man I suffered similarly as I was off a farm in Hampshire, not exactly compatible with what all the Geordie, Scouser and Glaswegian engineers had in mind for a budding Mar. Eng. Oh, now I see you are a Southerner as well.....double whammy old son!!!! Good on yer for sticking with it.

I also sailed with a Co. where I was the first non Scottish, Non RC and non Masonic Ch. Eng. that was ridiculously tough too. But an engineer wins out on performance so I must have rattled by some how.....

eldersuk
3rd May 2009, 22:40
The beauty of the timing valve Doxfords was that you could adjust them just by disconnecting the camshaft coupling and turning it by hand as you went along.
After disconnecting the discharge pipe there was a gadget which screwed on in its place and which held a clock gauge with an extension rod to the timing valve. Thus by turning the camshaft and referring to the index plate on the end you could find [1] the beginning of lift [2] the point and magnitude of max lift [3] the return to cam base circle. All these measurements could be taken with the fuel lever on various settings from stop to full speed and the whole lot transferred to a fancy multi coloured chart and taken up to the old chief just to annoy him!

Derek

Steve Hodges
5th May 2009, 20:36
The beauty of the timing valve Doxfords was that you could adjust them just by disconnecting the camshaft coupling and turning it by hand as you went along.
After disconnecting the discharge pipe there was a gadget which screwed on in its place and which held a clock gauge with an extension rod to the timing valve. Thus by turning the camshaft and referring to the index plate on the end you could find [1] the beginning of lift [2] the point and magnitude of max lift [3] the return to cam base circle. All these measurements could be taken with the fuel lever on various settings from stop to full speed and the whole lot transferred to a fancy multi coloured chart and taken up to the old chief just to annoy him!

Derek

This sounds familiar, the mists of time are clearing a bit!
I know that I worked out that you had to set the lift with a clock gauge and an extension, but I never thought of disconnecting the camshaft coupling, just turned the whole engine. Mind you, the Chief would have had kittens if anyone had suggested disconnecting the camshaft.
What bugs me (still!) is why wasn't this method in the manual? Whas it some perverse initiative test by some embittered soul in the Doxford offices?

hamishb
6th May 2009, 00:02
This sounds familiar, the mists of time are clearing a bit!
I know that I worked out that you had to set the lift with a clock gauge and an extension, but I never thought of disconnecting the camshaft coupling, just turned the whole engine. Mind you, the Chief would have had kittens if anyone had suggested disconnecting the camshaft.
What bugs me (still!) is why wasn't this method in the manual? Whas it some perverse initiative test by some embittered soul in the Doxford offices?

Hi Steve,as a wee reminder I have posted a picture of the dreaded timing valve. I checked an instruction manual and yoy are quiet correct it does not mention anything about disconnecting the camshaft. what it does say however in para 3 is "then by rocking the the shaft slightly each way measure, by means of feeler gauges" etc.,
Para 7 goes on " remove the setting adaptor (41) and re fit the fuel inlet pipe. RE-CONNECT the camshaft coupling to the reference marks.
I never realised that there no was instruction to disconnect the camshaft at the coupling as we always did the timing valves that way. One learns something every day
Also I see my picture seems to have reversed itself but it was all right when it left rainy Clydeside.
Correction and apologies the picture is reversed in my machine.
Regards Hamish

Duncan112
6th May 2009, 13:35
Don't recall ever measuring maximum lift but to save messing with DTI's and feeler gauges we used to run the priming pump to pressurise the fuel system and turn the engine until the roller follower just locked - this was the start of injection, when the roller freed off again this was the end of injection. If you were worried about filling the cylinders with fuel whilst doing this you could shut the supply valves to the timing valves save the cylinder you were checking. I was shown this method by engineers who had served their time as engine builders with Doxfords so maybe it had some basis in the yard.

Mention of DTIs and valve lift reminds me of Sulzer fuel pumps, which like their engines were (IMHO) best avoided.

Duncan

Satanic Mechanic
7th May 2009, 08:20
Don't recall ever measuring maximum lift but to save messing with DTI's and feeler gauges we used to run the priming pump to pressurise the fuel system and turn the engine until the roller follower just locked - this was the start of injection, when the roller freed off again this was the end of injection. If you were worried about filling the cylinders with fuel whilst doing this you could shut the supply valves to the timing valves save the cylinder you were checking. I was shown this method by engineers who had served their time as engine builders with Doxfords so maybe it had some basis in the yard.

Mention of DTIs and valve lift reminds me of Sulzer fuel pumps, which like their engines were (IMHO) best avoided.
Duncan

Duck -INCOMING

Yeesh Duncan - You're taking a chance there are you not!!!!

your right though - B&Ws are much better

Ian J. Huckin
7th May 2009, 15:21
your right though - B&Ws are much better[/FONT][/SIZE]

100%(Thumb)

Duncan112
7th May 2009, 20:52
Duck -INCOMING

Yeesh Duncan - You're taking a chance there are you not!!!!

your right though - B&Ws are much better

One is but a child of ones own experience....

B&W = Big and Wonderful

Mind you we seem to be getting sidetracked here - I think there was a thread a couple of months back about most favourite/least favourite engine - Paxman featuring heavily in the latter category.

Tin hat now on head,

Duncan

Satanic Mechanic
7th May 2009, 23:31
No - you're right.

Paxmans were the work of Satan himself

Doxford76J6
26th March 2011, 18:04
On the J type, disconnect the camshaft and use the fuel pressure from the priming pump to set timing and measure cam clearance. Leave vent screws open on the injectors.

Injection period is adjusted by changing the length of the rod between valve and control shaft by its differential threads. Commencement of timing adjusted by moving cam peak.

Take cards at sea at FSS and balance powers using the quadrant on the control shaft end of the control rod.

There, easy.

jim garnett
11th April 2011, 07:35
Spent 5 years at sea on doxfords in the 1950s,never saw a manual in all that time.Perhaps they didn't print them during the war years when the ships I were on were built.They would have been handy.

Jim Garnett

averheijden
23rd November 2012, 11:38
Mention of setting Doxford timing valves in the thread on indicator cards has re-awakened an old "niggle" that has been lurking at the back of my mind for the last thirty-odd years - perhaps some of you experienced Doxford fanatics can pt it to rest for me.
I only sailed one trip on a Doxford, it was a 1961-vintage six cylinder with scavenge air pumps, I think it was an LB model.
Steve,

DOXFORD LB with TIMING VALVES??, probably later converted with "timing valves"

I believe that the Port Sydney was also converted with Timing Valves?
And probaly more DOFORD'S, see:

http://www.youtube.com/watch?v=qdAcyQMa1EM&feature=related.

regards
ALFONS (http://users.telenet.be/doxford-matters)

Steve Hodges
26th November 2012, 21:49
Steve,

DOXFORD LB with TIMING VALVES??, probably later converted with "timing valves"

I believe that the Port Sydney was also converted with Timing Valves?
And probaly more DOFORD'S, see:

http://www.youtube.com/watch?v=qdAcyQMa1EM&feature=related.

regards
ALFONS (http://users.telenet.be/doxford-matters)

Alfons,
I always understood it was an LBD type Wallsend-Doxford, built 1960/61. It certainly wasn't a "P" or a "J". However. on checking in other dark corners of SN, I find that one contributor identifies this particular engine as " 6-cyl. 2 S.C.S.A. 700 x 2320". So what was a "2 S.C.S.A."? A Wallsend variant on the LB/LBD, maybe?

OliverD
27th November 2012, 01:47
2 S.C.S.A. I understand that as describing a 2 stroke cycle, single acting engine.

Oliver

averheijden
27th November 2012, 10:39
Alfons,
I always understood it was an LBD type Wallsend-Doxford, built 1960/61. It certainly wasn't a "P" or a "J". However. on checking in other dark corners of SN, I find that one contributor identifies this particular engine as " 6-cyl. 2 S.C.S.A. 700 x 2320". So what was a "2 S.C.S.A."? A Wallsend variant on the LB/LBD, maybe?

Steve and Oliver,
I think that 2 S.C.S.A means in this case:
2 cycle, Super Charged, Single Acting, because it was a LBD with "Timing Valves", one camshaft and C.A.V fuel Valves, I suppose?

First fuel accumulator pump installed on the "British Craftsman" (built 1951), with 4 cylinder DOXFORD, 600LB4, Stroke 2320 mm, 3300 BHP at 108 revs/min. Supercharged (1953)

Do you still remember the name of that ship, and was the Doxford Engine Super Charged?

Regards
Alfons

Steve Hodges
27th November 2012, 19:19
Steve and Oliver,
I think that 2 S.C.S.A means in this case:
2 cycle, Super Charged, Single Acting, because it was a LBD with "Timing Valves", one camshaft and C.A.V fuel Valves, I suppose?

First fuel accumulator pump installed on the "British Craftsman" (built 1951), with 4 cylinder DOXFORD, 600LB4, Stroke 2320 mm, 3300 BHP at 108 revs/min. Supercharged (1953)

Do you still remember the name of that ship, and was the Doxford Engine Super Charged?

Regards
Alfons

Alfons,
It was the Border Pele of 1961 ( Common Bros/BP ), and it was aspirated by air pumps, no turbocharger.

Hamish Mackintosh
27th November 2012, 22:41
A little off topic but still with Doxfords, I was on the British Splendour circa 1954/5, and on the wheel as we approached the pilot boat off Oslo(could have been Brergen)the old man told the Second mate to "slow her down a bit" the second mate rang down for half Ahead, but nothing happened(one can feel the "pulse" of the engine thru the duckboard one stands on at the wheel)with the pilot boat now quite close the old man told the second mate to "stop her"which the second mate duly rang for, but again nothing happened, altho the engineroom had rung back on both movements of the telegraph, the old man let a screech out of him like a wounded turkey, and yelled at the second mate to get on the phone to the engine room and find out what those #### engineers were playing at, as the pilot boat shot by us down the starboard side, and the launch scrambling to get out of our wash, the second mate reported to the old man ,"the third says he can't get her stopped sir""well he had better get her stopped now or we will be into the side of a mountain in less than a mile" to cut a long story short we did get her stopped and full astern ,(to the tune of I thought we were going to break in half she was flexing so much) But my question is WHY would the Doxford not stop? There was a meeting of the old man, the chief , the second engineer, along with the third engineer and the second mate in the old mans day room ,The next morning and altho there was much weeping and wailing and nashing of teeth at the meeting, nobody ever found out what had transpired. We came back to the Tyne for drydock right after discharging and tank cleaning, so there was very little time to find out anything