Category Archives: Leak Hints & Tips

Notes on Drawings and Design
While in my opinion the Leak Compound is the best marine compound design on the market, it seems to be quite well known that there are a number of errors (and omissions) from the drawings for the Leak Compound. As a service to the community, I am publishing the errors I have found in the drawings and would welcome input from others as to any “quirks” they have found.

In the process I have also developed a reduction drive for the pumps (to allow the engine to rev faster) and a step-up drive for an alternator to provide power for burners, navigation lights and radio – creating the drawings for this have taught me not to be too critical of others mistakes – it’s hard … :-)

Stud Clash on LP Valve Chest

There is a clash in the drawings between the bolts holding the reversing lever slider pivot (shown in the scrap drawing on page 33 of “the book” entitled “Reversing Arrangements”, and numbered item “2”) and the upper-right stud securing the LP Chest to the LP Cylinder….

Having hit the problem, I moved the pivot in-board about a quarter to miss – I now have an ugly hole to plug 😦

Also take care, I think the original hole locations in the pivot are also incorrect, as they seem to result in the slotted arm (item 3 in above drawing) fouling the studs on the LP valve cover. So I made mine (the 2nd one!) a bit longer and located holes by eye.

Eccentric Rod: Part 14

  • BOOK, NEW, OLD?, ME? Colin Sims analysed that the length of the eccentric rods appears to be wrong as follows: “The eccentric rod issue I worked out in the following way: Link radius is 7.5″, with a ‘backset’ (not the right term, I know) to the pin holes of 3/4″, leaves a dim of 6 3/4″ from the pin to the crank centre. If I add the dim from the centre to top face of the eccentric strap to the foot to pin hole dim on the rod, I get 6 5/8″, i.e. 1/8″ short. This will not affect the valve travel, as this is determined by the eccentric throw, but it would affect the quasi-SHM of the valve movement subtly. Yes I know it is not true SHM, as the mechanism is effectively a slider-crank form.editor’s note: I have made the rods to the drawings, and they seem to fit, but I agree with Colin that the math sais they may the wrong length.
  • Having now assembled the valve gear (February 2014) I fear that this is proven – moving the gear from ahead to astern cannot be accomplished without the valves being deflected in mid gear, no matter where the crank is set. I think this is wrong, ah well, time will tell – I have managed to time the engine to run on air, but pretty roughly so far….

Drag-Link Bearings: Part 16

  • BOOK, ME & NEW: From John Olsen (NZ) – “I have built a Leak engine (with mods) from the original 1980-83 ME articles. One mistake in the drawings there was that the pins at either end of the drag links are not long enough. This means that the drag links would foul on the pins in end of the eccentric rods. This is on page 707 (ME). Part 16 “drag link bearing” has a dimension of 1′ between the two grooves. The pins at the end of the eccentric rods is 1.25″ long plus the head, which is not dimensioned. For this to fit between the drag link rods, the 1″ on part 16 must be increased to at least 1.25 inches.” Submitted John Olsen –
  • editor’s notes: Also submitted by Colin Sims, he comments:  “I think the eccentric rod pins that John mentions are overly long too – I think they would work at 1″ if they just needed to fit over the eccentric rods outside dimension o but the heads and lock nuts mean that the pins need to be lengthened, but perhaps not as much.”
  • John Olsen also sais: “Not an error as such, but those drag links are excessively fiddly. They look good when together, but there are a lot of small parts when you have to assemble and disassemble them.”
  • editor’ s notes: Having now completed these parts, John and Colin are certainly correct – the drag-link pins DO need lengthening, I went for 1.25 inches, but actually this proved too tight, as the joggle in the HP valve-rod also clashed, some careful thinning of this component has provided the needed clearance. This is a complex and fiddly assembly, and a pain to work on – but it does look nice!

Front Columns: Part 4

  • Diameter of Columns BOOK, NEW,ME, OLD: There are no diameters for this – while this is not “critical” it does leave one at a bit of a loss as to the size of stock one should start with. I decided on 1.125dia at the top and 1 5/16 at the bottom – IMHO wider is better, as I was surprised at the amount of “flex” in the erected engine, even with everything “dogged up tight” – maybe this is a good thing – who knows…. Submitted by Malcolm D

Cylinder Top and Bottom Covers: Parts 5, 6a & 6b

  • BOOK: The stud locations for the covers are not well dimensioned. Care needs to be taken as they can break into the ports. This is particularly likely to happen as the covers are drilled first and then spotted thru to the cylinders, and the clash is not obvious until it is too late…
  • BOOK: Similarly, the holes in the lower covers to attach the covers to the rear columns are not dimensioned at all! I concluded that the two outer ones should be 1.875″ from the cylinder centerline and the centre one 2″ from the cylinder centreline – this worked OK for me…
  • BOOK: Two of the cover bolt holes on the lower HP cylinder cover (and one on the upper HP valve chest cover) are shown as blind – this can’t be right!

LP Valve Chest: Part 3c

  1. Cover Studs: Colin Sims (another SBA Leak builder) reminded me of this one – The LP Valve Chest Cover is attached to the Chest by 12 studs; and the chest is attached to the cylinder by 8 (EIGHT)…. the two at the top and bottom cannot be attached as the studs clash with the ports. So as I wrote at the time “It may be that my Technical Drawing A-level from the ’70s was to a different standard but only 8 of the 12 holes for the valve chest cover mounting holes should be drilled through. The 8 down each side do carry through to the block, but the 4 at the top and the bottom, should be blind – as they “clash” with the port pockets.“…. Moreover this also means that the stepped studs shown in the drawings should only be used on the sides (the top and bottom are plain studs as the larger ones would (do) clash with the stuffing box and tail rod)… Lastly in the BOOK (at least) only the four right hand holes are shown threaded – in fact the left hand ones need to be too (to take the aforementioned stepped-studs).
  2. The Lap: The ports as shown in the BOOK, have an undimensioned dimension indicating where the “LAP” is/can be measured? There is no indication of what this should be…but see below….Update: I found the lap and lead dimensions at the end of the Book in the valve setting section, Lap is given as 3/16″ and the Lead as 1/32″, but still not sure of the implications of the LP port height issue noted below.
  3. The Port Height: This is dimensioned in two places as two different sizes! I have only just realised this. I noted that the ports on my valve chest were 3/8″ high, and that this did not match the 5/16″ dimension shown on page 10 (of the BOOK) I thought this was just a blunder on my part. But tonight as I am writing this page, I realised I cut them this size because they are shown as 3/8″ high (on page 7 of the BOOK). Lord knows which is right, perhaps they are meant to be tapered! This will mess with the LAP, I guess I am going to find out when I time and steam the engine!

HP Valve Chest Part 3d/3a

  • BOOK  (not sure on others) – The “HP Valve Chest Face” drawing shows 5 ports. The upper one is shown in error – there should only be four ports in 2 symmetrical pairs. This would be a a disastrous error and mean scrapping the casting. The drawings variously number the HP valve chest as 3d and 3a. Submitted by Malcolm D
  • John Olsen comments “I didn’t like the porting on the HP valve to get the steam from the end to the middle, so both of my piston valves have an end cover top and bottom that provides a connection for a decent size external pipe. This is based on the idea that a decent size connection to get the steam out is often more important than getting the steam in.” editor’s note: To avoid confusion I should explain that  John fitted piston valves to HP and LP on his engine, hence his “both valves” comment.

Rear Columns Part 3

  • BOOK and NEW (not sure about ME) – the horizontal distance from the front of the foot of the column to the slideway face is shown as one and five sixteenths (1 5/16″) but it should be one and fifteen sixteenths (1 15/16″) – Submitted by Malcolm D
  • BOOK and NEW (not sure about ME) – the width of the pump mounting blocks is not given, I THINK it should be 2.25 inches (1 1/4″) – Submitted by Malcolm D