FH Crankshaft 2 Cleanup 2 - Sludge Traps & Galleries

Having got the crankshaft to a stage where I believe it is mechanically acceptable, we now turn to a vital area which is easy to overlook if you are not listening to advice or reading the books.

The ubiquitous crankshaft sludge traps - large drillings in the crankshaft which are designed to centrifugally extract solids from the circulating oil, and keep it out of harms way. These days, we use high-detergent oils and filters - the oil carries solids in suspension and the filter collects it, and there's the rub - when filling your barn find with new oil you really don't want the modern oil releasing the built up deposits of the last 50 years into your lubrication system, so you must clean the traps and banish the sludge forever before you run the engine. Never more true than if that engine belongs to an Ariel Square Four, which has very small (3/16" diameter) sludge traps.

No one wants a seized big-end, as the appearance of a connecting rod through your crankcase can be upsetting to younger viewers.

In an FH, A10 or A7 crankshaft, and many others, the sludge trap is in a large drilling through both big ends which is closed with a threaded plug at each end. The big end oil feed comes into this gallery from the timing side main bearing, and both the big ends are fed by 3/32" ports drilled directly into the gallery.

The gallery is provided with a thin tube, which acts as an oil way; until it is very blocked, the solid deposits form outside of this tube, flung away from the centre of the crankshafts rotation as you would expect. The tube features two or four holes to distribute oil to the big ends, and another hole by which it is located by one of the flywheel bolts, and one end is belled out to locate it in the large diameter of the gallery.

The tube is located at the drive side end on one of the gallery's closing plugs. The plugs are soft mild steel, very tight, often staked in and they are optimistically equipped with screw driver slots. People tell you not to bother with your impact driver - I tried it once, destroyed the slot and reached for the welder. The welder, however, is not the only way.

I started this morning with the 100 mm grinder, with a twisted wire cup brush in it, to clean up the rust (I also had it on the rear mudguard, but that is another story for another day).

My usual approach to these is to weld a bit of 1/8" sheet into the slot. This bit of 14 swg bar was a bit small, and it wasn't clean enough:

Grab it with an adjustable and turn...

And Robert is revealed as one of your mother's siblings.

That is the timing side. The drive side, at the end of the oil way, will be worse. I loosened this plug using the 'welded bar' method, but broke the bar trying to get it out. The moral of the tale there is to take more care - make a suitable bar and weld it in to a prepared slot. Or, as I did here, drill two 1/8" holes, about 3/8" deep; grind flat the ends of two thick masonry nails (hard, and very useful), and use them as a makeshift pin spanner:

Here's another approach: Vincent van Ginneke sent me this picture; he's using a large vice to hold a 1/2" drive screwdriver bit in the sludge trap plug slot. Normally, if you try a screwdriver the bit will  slip out of the slot in the plug; Vincent clamped the crank, screwdriver bit and T bar in a large vice, with just enough pressure to prevent it from dropping out and by turning the T bar a tiny bit (about 1/8th of a turn) and opening the vice also a tiny tiny bit he was able to hold enough pressure on the screw driver bit that it would stay put in the slot.

As I mentioned earlier, the drive side is worse - it's totally full:

The plug on the right is the drive side one. The nose locates the end of the sludge trap tube:

Because the tube is surrounded by solid deposits, it can be hard to shift. A hammer and a drift can be useful here - you can see the tube emerging on the left:

And that is it. That's most of the contents of the tube - the rest of it is still inside the crankshaft.

You'll want to scour that out, like this:

You also want to make sure the oil ways are clear. This is a 3/16" twist drill going through the timing side main bearing oil way, clearing the path to the sludge trap gallery. You can just see it emerging in the gallery:

You can clear the big end oil ways with a 3/32" drill.

When new, these oil ways have a 'teardrop' scooped out of the surface to distribute the oil across more of the big end width. Since these are -0.030", these 'teardrops' have long since been ground out. We can put them back with the Dremel:

When we've done, we'll polish the surface with Emery and wet'n'dry.

These are the flywheel bolts. One of them (guess which one) holds the sludge trap tube in place - that is a 3/8" BSCY intermediate tap, waiting to clean up the threads.

Both the bolts and the female threads in the crankshafts are easily cleaned up; I may replace these bolts when I assemble the engine.

The final step is to clean the remaining rusty debris from the flywheel and the crank webs, with various wire brushes. This done, I've sprayed the parts with ACF50 for storage - we'll put it all together when we come to assemble the engine.

Thanks for reading, and I hope you found it useful.

Get out there and use your bike!

Big Open Spanner

My ER40 collet chuck needs two tools to operate it - the 'E spanner' to operate the castellated locking ring and a 15" adjustable to hold the flats at the rear, which are 46 mm AF.

I don't have a 15" adjustable. Well I do, but it's a 1940's style spanner and is much too thick to go between the chuck and the lathe spindle backplate. I could buy one, but a decent one is at least £25 and car boot sale season is a way off yet. So what about buying a large open spanner? Could do that too, but where is the fun in that?

Lets make one.

We'll start with some 25 mm x 6 mm flat bar, and chop up three bits with a cutting disc. In the same operation, we'll round the end of one piece.

When Brokkr's fires have died to a mere smoulder, and I can pick up the parts without burning my fingers, we have this:

These three parts will make up the handle and the two jaws of the spanner. You could cut this from 1/4" plate, but you would waste a lot of material. This is one of those production engineering decisions which pan out differently according to your needs - I am happy to spend a couple of hours fabricating this and using some scrap bar (actually a threshold plate that I robbed from a skip) rather than use most of my stock of 1/4" plate.

So, I've laid it out on a large bar magnet to plan the shape:

Holding the collet chuck in the vice, I've sketch around it to come up with this. At this stage, the aperture is drawn to about 40 mm - we will trim it to size when it is all together.

You'll appreciate that it is much easier to cut the shape into these jaws with them loose. I've used a cutting disc, a saw, the grinding wheel and a belt sander to get to this stage:

This is ready to weld. The original bar is galvanised - most of this has been sanded off as it will burn, contaminate the weld and poison the operator.

Setting up for tacking. The handle is in the vice; a piece of scrap is clamped to the handle, and the two jaws are clamped to the scrap. You'll notice there is now an 8 mm hole for hanging the spanner up. The job is set up so I can rest my wrist on the vice:

I've used the TIG set to weld the jaws to the handle with a 2.5 mm tungsten ground to 90 degrees, a #4 shroud and Argon at 5 l/min. The welder was set to 60A DC. I made about half the weld on one side, removed all the clamps, flipped the spanner in the vice and made the whole weld on the other side, then flipped it back and finished the first side. Then I made the short welds at each end of the joint. All joints were closely prepared with no gaps and welding was entirely autogenous - no filler rod was used.

I'll use some U-Pol etch primer on it now, to prevent rusting.

Next job is a festival of filing and grinding, checking very frequently against the collet to come up with a good fit. I could improve that curve some more, but it is pointless...

I found this green at the back of the shelf. It's old, it's revolting, but it's free.

I hope you like it.

FH Crankshaft 2 Cleanup

Despite my initial suspicions to the contrary, it seems you can get an FH crankshaft in the mini lathe as shown in this first attempt, below. I'm not going to do anything radical here, but I can use the lathe to clean up the oil pump drive and the journal for the timing pinion - and I might use it to polish the big end journals.

We can improve this set up though, with the collet chucks and the fixed steady, but first we need to identify the jobs we want to do and work out the sequence of events. The jobs I have in mind are these:

1. Set up the timing side bearing in the chuck and use it to centre the fixed steady
2. Cut an oil way in the bearing
3. Measure the run out on the oil pump drive thread
4. Clean up the crankshaft pinion journal, supporting the timing side main in the fixed steady and holding the crank in the ER40 collet chuck
5. Polish the big ends
6. clean up the oil pump thread and the crank nose
7. Clean up the drive splines and the drive side journal with the crank in the ER25 and supported on a revolving centre
8. Clean up the webs on the bench, with a wire brush
9. open and clear the sludge traps on the bench
10. Clean the crank in the parts washer and check thoroughly

This arrangement shows the crank in the ER25 collet, and demonstrates a 0.28 mm run out in the timing side bush - this is not real, and is due to the fact that the pump drive thread is a little bent. The effect is magnified further from the bend point.

While we have it set up like this, we can clean up the drive splines and the drive side main bearing journal, which has a burr on the thrust face:

Easily skimmed off with a suitable tool.

We still need to measure the run out in the oil pump drive thread, so it's better set up this way:

Here's the crankshaft set up in the ER40 collet chuck, with the timing side bush in the fixed steady. Afetr this stage, I cleaned up the timing pinion journal and the timing side main journal, where the tming pinion butts up to it to get the timing pinion to sit in it's proper loaction. I put the DTI on the crankshaft timing pinion, in a plain section and showed a runout of 0.01 mm, or 0.0004".

With the worm in place, I'm measuring the runout on each of the six flats of the worm drive:

I am recording the results in my notebook, and subtracting values from opposing flats to come up with the deflection of the crankshaft nose. We can see from a comparison of the 0.01 mm timing pinion journal with the 1.0 mm runout of the worm drive thread that the nose is bent - obvious to the naked eye, but now we can quantify it:

Notebook with side order of pizza

These figures include the dimensional tolerance of the worm drive hex, and the clearance in the thread so we can expect the values to be excessive. Adjusting the nose alignment, I eventually got the run out on the hex to 0.5 mm and the runout on the plain portion of the drive thread to 0.12 mm:

The run out in the thread is no longer obvious - probably good enough I think. I took this opportunity to true the very end of the nose and to recut the centre drill hole in the end of the crankshaft. This gave me the opportunity to set the crankshaft up between centres and to skim off a burr on the timing side thrust face.

With the lathe set up like this, it is easy to skim

That's it for the crankshaft at the moment. 

Swapping back to the 3 jaw chuck, I have an opportunity to look at the timing side main bush. As we saw, the oil holes don't line up with the remains of the gallery in the journal:

The plan is to cut a gallery in the bush, to bridge the bush oil holes and the journal oil holes. We can do this with a boring bar:

We'll take the opportunity to true up the thrust face of the bush as well. Here's the end result. If this bush fits in the crankcase, we'll have to decide whether to use it or not, but it has a few unpleasant scrapes. It may end up being a practice piece while I make another.

FH Crankshaft 3 Review

Confusing isn't it, all these crankshafts.

Number 3 is another small journal crankshaft I have acquired.

It's missing a few flywheel bolts, but at least someone has released one of the sludge trap plugs.

Now, before we go any further we need the reference dimensions for comparison with the results of the dimensional survey. Here's the data sheet again:

The timing side journal in this one looks fairly good and measures 1.355" in several positions, which would grind to -0.020"

The oil pump drive thread and the timing pinion journal will clean up I think.

The big ends vary a little - 1.418" on the timing side and 1.417 on the drive side, which is about -0.040"; Drags have shells down to -0.050", so these could be used one way or another.

The splines, drive side main and shock absorber thread will clean up ok.

FH Crankshaft 2 Review

A while back, I dismantled and measured up the small journal crank that came with the 1955 engine I have in my 1958 FH kit, now christened 'Crankshaft 1'. The post is here: https://ariel...small-journal-crankshaft.html.

As we discussed, the 1958 cases should be fitted with BSA's new large journal 'Rocket' crankshaft and in view of the wear on the 1955 crank, considerations of originality and the fact that a well known retailer had a standard large journal crank available at a very reasonable price led me to replace it.

Here it is; no flywheel, somewhat rusty...

Of the three crankshafts I have, this is the only large journal crank. We'll call it Crankshaft 2.

It's got nice looking splines and drive shock absorber thread:

Less nice - looks like the pump drive end has had an argument with Thor, King of Hammers and not come off too well. And why is that bearing stuck half way along the journal?

Other than that, no new horrors, but we need to understand what we are aiming at. This BSA service sheet gives us the dimensions we are aiming at; small journal cranks on the left, large journal on the right:

We need to get it up in the vice and clean it up.

First job is to get some oil on that bearing and pull it off. We need to decide if this crank is a pile of scrap and the ashes of burned currency or whether it will become the foundation of my new bike's engine.

Cleaning the surface rust of the big end journals reveals some smooth surfaces, with no score marks, but with small rust pits:

Both of these journals are 1.655" - 1.656" diameter, measures in several places - which equates to an unworn -0.030" grind; not the standard cranks I was hoping for but usable nonetheless. We'll need to polish them but for now we can tick that box.

Next is the dubious looking oil pump drive thread. It's 9/16" - 20 CEI, left hand - no chance of finding a die for that, unless I buy one and that in itself might be a problem. I could clean it up in the lathe, but that will be another challenge as the end has felt the hammer and the centre drill hole is deformed and probably wont fit the dead centre in the tailstock - so we'll need to buy a fixed steady if we are going to try that approach. Breaking out the thread files cleans the end up nicely enough that the old oil pump drive fits beautifully and reveals their is still enough thread for the lock nut.

Next stop, the timing side main bearing journal. Unfortunately, this measures 1.242" - which is about 120 thou undersize. I can make a bush to fit it, since it's in good shape but is it safe to use? If I use it I will have to recut the oil way, since that has virtually been ground away.

The thrust face is a bit untidy - there is a small ridge which will clean up.

Thinking about this, I've realised that the drive side journal is 1.18", with all the bending load that is subject to from the primary along with the cyclic loads from the power stroke. I guess a 1.242" timing side journal will always be OK.