Model Diesel: 32mm bore, 38mm stroke, indirect injection

[Nerd1000]

Rework of the crankpin by lapping:

Fixtured on the lathe

Quick and dirty 2 piece OD lap.

So far I've removed the taper but introduced a bit of hourglass shape that needs correction, probably because my lap is a bit too wide. I'll mill it thinner before continuing.

 

[Steamchick]

I have thought that a hole in the crank web could be used as an oil pick-up - but would the splash of dipping the crank web into oil simply lose power by splashing oil everywhere? My "teacher" told me that he thought pick-ups rarely worked as all they really did was splash the oil around so the crankcase was full of spray and everything was washed in oil, thus working its way into big-ends, etc. He replaced bent tubes on some big-end caps with fine (1/8in?) steel pins, as he said the spray was adequate and the engine lost less power in splashing oil around. He figured that when running at speed, the oil didn't have time to flow back into the groove in the oil made by the dipper, so the dipper just scraped the edges of the groove in the oil and flung it about.... So oil spray around the big-end simply crept into the bearings as it does...
K2

 

[Nerd1000]

To tell the truth I only put the pick up in because I've seen it on other engines. In other discussions it's been pointed out to me that centrifugal force will probably stop oil from going up the drilling any time the engine is spinning fast. But on the other hand, it might be somewhat effective at low speed.

I got the crankpin more or less sorted (at least to the point where I was having trouble telling where the lap was working). That didn't totally solve my binding issue, but did improve matters markedly. So now I'm scraping the bearings to match the crankpin.

You can see a little residue from my prussian blue dye on the surface. They probably need one more pass to get the fit 'perfect' but the engine would be runnable with them as-is.

 

[a41capt]

Nerd 1000,
I know I’m coming into the thread late, and without much info to offer on diesel, but I have a question for you regarding a term I heard from a long-dead engineer neighbor. He mentioned something called a “perfume diesel”, and I’ve never found anything referring to this type of engine. As I’m sure you’ve done a lot of research on the diesel engine, can you enlighten me on this type?

Thanks in advance,
John W

 

[Mechanicboy]

To tell the truth I only put the pick up in because I've seen it on other engines. In other discussions it's been pointed out to me that centrifugal force will probably stop oil from going up the drilling any time the engine is spinning fast. But on the other hand, it might be somewhat effective at low speed.

I got the crankpin more or less sorted (at least to the point where I was having trouble telling where the lap was working). That didn't totally solve my binding issue, but did improve matters markedly. So now I'm scraping the bearings to match the crankpin.View attachment 147075
You can see a little residue from my prussian blue dye on the surface. They probably need one more pass to get the fit 'perfect' but the engine would be runnable with them as-is.

Nerd1000, ..You can't make perfect fit, let running-in the engine improve the tolerance between the bearings and shafts to a perfect fit who are impossible to make with the tools.

 

[Nerd1000]

Nerd 1000,
I know I’m coming into the thread late, and without much info to offer on diesel, but I have a question for you regarding a term I heard from a long-dead engineer neighbor. He mentioned something called a “perfume diesel”, and I’ve never found anything referring to this type of engine. As I’m sure you’ve done a lot of research on the diesel engine, can you enlighten me on this type?

Thanks in advance,
John W

I've not heard that before either. Maybe he just liked the smell of the exhaust?

 

[a41capt]

LOL! He spoke about how efficient it was, and I wish I’d have pushed him further, but I didn’t have the same level of interest back then.

 

[Roger B]

A very wild guess would suggest that he was talking about air blast injection engines. In days gone by perfume used to be dispensed with a pump from little spray bottles with with a multi hole nozzle a bit like an air blast injection nozzle. Total conjecture

 

[a41capt]

I don’t want to hijack this thread, thanks for your patience Nerd1000!

If I find anything else out, I’ll start a new thread, and anyone with further info is encouraged to message me direct.

John W

 

[peterl95124]

The flywheel will have a simple parallel bore and will be retained by a big nut on the crank. The way I've made it is slightly cursed, it's a 15mm diameter... with a 18 TPI thread cut into it. I'm probably going to engineer hell for that one.

Oh the Irony, LOLROTF, !!! !!! !!!

(I think you're going to heaven for giving us such a good laugh!)

 

[peterl95124]

Nerd1000,
I really like your technique for lapping the journal, I'll be remembering that as I sometimes have needed something like that but didn't come up with anything workable like you did.

I often lap my bearings with 800 garnet paste and a rod that's the same diameter as the shaft journals, slowly tightening the bearing bolts as I turn the shaft also with some in-and-out motion, usually one application of paste does it sometimes two (then clean the heck out of it with toothbrush and detergent), leaves just the right amount of clearance for oil, silky smooth in the end. (I use a rod, and not the actual crank or cam shaft, because for cylindrical lapping axial motion is just as important as rotational)

Peter L.

 

[petertha]

So now I'm scraping the bearings to match the crankpin

Can you show the tool that accomplished those internal round surface scrapings?

 

[Nerd1000]

Can you show the tool that accomplished those internal round surface scrapings?

It is forged from an old file. Cutting edges on the side, hollow ground on the bottom.

 

[Nerd1000]

My reamers arrived, so I turned the pin bush from 954 aluminium bronze and pressed it into the conrod, then drilled the oil hole through from the top of the rod. That assembly is now finished!

Next will be the main bearings and their mountings. Then I suppose I'll have to start thinking about machining the block...

 

[GreenTwin]

My reamers arrived, so I turned the pin bush from 954 aluminium bronze and pressed it into the conrod, then drilled the oil hole through from the top of the rod. That assembly is now finished! View attachment 147281 Next will be the main bearings and their mountings. Then I suppose I'll have to start thinking about machining the block...

That is a beauty !

.

 

[peterl95124]

My reamers arrived, so I turned the pin bush from 954 aluminium bronze and pressed it into the conrod, then drilled the oil hole through from the top of the rod. That assembly is now finished!

Nice !,

BTW, I have experienced hole shrinkage after press fitting a bearing or sleeve/guide, have you checked since pressing ?

 

[Nerd1000]

Nice !,

BTW, I have experienced hole shrinkage after press fitting a bearing or sleeve/guide, have you checked since pressing ?

When you press a bush into a hole two things happen: the bush gets compressed, and the material surrounding the hole gets stretched.

If the housing is significantly stiffer than the bushing the stretch factor is usually minimal, and the interference is absorbed almost entirely by compressing the bush. I.e. 2 thou of interference will result in close to 2 thou undersized bore.

I re-reamed the bore after pressing, which resulted in it being exactly on size.

 

[Nerd1000]

The main bearings and their mounts are done. Here's a photo of the crank mounted up in them. The front bearing mount also holds an oil seal for the crank nose.

The astute reader may notice the extra holes in the rear mount. Those are for weight reduction, and are definitely not there because I didn't tighten the vise enough when drilling leading to the part moving and spoiling the hole pattern on the first attempt. No more questions please.

As the rear bearing mount is hidden by the timing gear case on the assembled engine, those 'weight reduction holes' won't be visible in the finished product.

 

[Nerd1000]

So upon reviewing the drawings I've got a feeling that there isn't enough meat in the crankcase around the bolt holes for the bearing mounts. It would be easy to treat this by simply moving the bolts, but it would come at the cost of having to remake the parts I just posted.

Alternatively, I could make the clearance holes for the bearing mounts smaller. What to do, what to do...

 

[Nerd1000]

A bit more progress. I bored the hole for the cylinder sleeve in the block.

Machined the cylinder sleeve from ductile iron:

Finally, I re did the mains.