Mercedes-Benz W165 Grand Prix engine in 1:3 scale

[Jasonb]

Nice adjusting tool, best not say that I flicked my nut round with the point of a scriber

Looing forward to seeing how it cuts.

[Vixen]

Ha ha,

The 'Microbore' adjusting tool seems to be a big hit

My 'Microbore' inert is buried deep inside the bar and also the crankcase. The depth graduations were impossible to see; so a long adjuster with an external dial were needed. I found some elegantly tapered scrap parts in the 'come in handy one day' draw. I think I made several of them for my late son's custom bike, now they have found an alternative use.

I have seen the 'bearing on crankcase' method used by vintage car restorers to line bore main bearing caps and a similar method used to bore the steam cylinders of full size locos.

The only problem I foresee, is the need to remove the crankcase and one bearing block whenever I need to get inside to measure the bore diameter. The end bearing block was made with a tight fitting spiggot so should re-position accurately. 

Achim, thanks for the reassurance that even a 0.02 mm adjustment is easily achieved

Mike

[Jasonb]

Mike, could you make a plug gauge with a hole in it that is just large enough to slip over the bar then you can slide that into position to check bore size without having to take things apart if you leave it within the crankcase.

[Vixen]

Jason,

Thanks. That's an interesting idea. There is a 9 mm 'dead space' at the front of the engine beyond the front bearing cap, which is not swept by the cutter. I could make a coaxial plug gauge to fit in there, which would act as a simple 'Go/No-Go' gauge. There is barely enough room for a stepped plug gauge which would give an indication of the required final depth of cut.

I will make something up and see how it looks. I would much prefer a measurement to a gauge.

Mike

[Vixen]

Maybe, just maybe, if I make up some additional L shaped jaws, I could use this spring loaded internal indicator to measure the bores in situ. I should end up with a 2mm gap between the bar and the inside bore. Should be just enough room for the new jaws.





Mike

[bent]

Mike, that line boring jig is a neat idea, thanks!  PS - have not been following this thread much, as this is an order of magnitude above my skills and abilities, but do occasionally pop in to see the progress.  Hoping to see/hear it run someday, keep up the good work!

Edit: re-re-reading what you wrote...any reason not to use ball bearings instead of plain aluminum bores?  I guess cost and the fact the block needs to slide as well as rotate along the bar?

[Vixen]

Bent,

Thank you for your comment, and I also read your piece on the 'response' topic. As you say; you must never forget to learn and learn how to learn from others. My machine shop skills are all self taught, mostly from reading model engineering magazines and from forums like this one.

28mm ball bearings, to carry the boring bar, are not a common size so i opted for plain bushes. I could have made and fitted bronze bushes. However I went for the simplest approach, to run in plain aluminium. They only have to last long enough to do the two engines. You could call it value engineering?

Today, I did the lathe installation. Three jaw chuck at one end and a live centre at the far end. A side link from the engine attaches to the toolpost; the connection allows some flexibility. The crankcase needs to travel some 160 mm (6.5") I have tried a feedrate of 150 mm/ min and a spindle speed of 300RPM. Everything is well oiled and runs smoothly and feels under control. However, both parameters can be easily changed, as necessary, when I start to cut metal.






Mike

[Jasonb]

That sounds quite a high feed rate at 0.5mm/rev, I would have been thinking about 1/10th of that or less

[Vixen]

Jason,

You are quite right about the high feed rate. I need to think lathe not mill. 150mm/min would be more appropriate to a high speed milling cutter than to a single point boring bar.

However, it served it's purpose to prove the set-up before cutting metal. I hope to do some of that before the end of the week.

Mike

[john mills]

Hi
I like your set up   you seem to have measuring sorted not easy when there is now room.I often had to use inside callipers .The feed rate .5mm Per rev was what was used often for rough cuts on a cnc machine i used at high spindle speeds that can remove metal quickly  but that was a good-sized machine whith the guard shut.
  John

[Hugh Currin]

Mike:

I like the boring set-up. It eliminates the shimming of the cankcase to the exactly right height when clamping to the carriage. Nice.

I was going to ask about measuring the bore, but that was answered. I do like the idea of a plug gage for this.

Glad to see you back on this project. Plan to follow as Internet allows.

Thanks.

[Jasonb]

It's not just the single point that reduces the feed rate, its the rpm and at 300 on the lathe instead of 3000 you might use on the mill you would want 1/10th. of the feed rate. 0.5mm pitch per rev is getting into thread cutting

Another thought on the measuring, as you are quite tight for space and just running the tool in plain aluminium would a small nick in the tailstock bearing plate be worth adding. That would allow the bar to be withdrawn with the tip of the tool still projecting without unscrewing the two bearing plates and risking them going back slightly out of position. This would allow whatever form of measurement you want to take or test fitting the bearings.

[Roger B]

An interesting set up    I await the first cuts   

Henry Greenly showed a much more basic version for boring without a cross slide including an automatic feed.

[Vixen]

Jason,

I noted your comment about feed rate the first time around. I moved the boring bar through the crankcase at 150 mm/ min to check for freedom of movement etc. Even so, it still took over a minute to traverse from one end of the crankcase to the other. And yes I will reduce the feed rate when I start cutting metal but most of the time it will only be cutting fresh air between the journals.

Hugh/ Roger.

This guided boring bar method is quite common in full size and oversize marine engineering, where the engine block (or whatever) is too large to fit on even the largest lathe. It also has the advantage of eliminating the shimming and alignment problems associated with clamping the block onto the carriage. It is less commonly used for model engineering but not unknown. Roger, what was the publication date of Greenly's book? 1915 or thereabouts.

Hugh, I have lost touch with your movements. Are you still traveling and exploring?


Mike

[Hugh Currin]

Mike:

That's OK, I've kinda lost touch also. But here's the cliff notes summary.

The Pandemic threw a monkey wrench in our 2020 travels. We did buy a house in Prescott, AZ and spent the summer there. That gave me a chance to move machines from Oregon and set up the big shop. I also decided, since we're spending 4-5 months a year in Brenda, AZ, outside Quartzsite, and have a permanent shed, that I should set up a small shop there. I obtained a Precision Mattews PM728 (benchtop Taiwanese mill) and a PM1022 (10" Chinese lathe). Over the winter, in Brenda, I bought a CNC conversion kit for the mill, added steppers and a controller and have it running. I'm also CNCing the lathe which has taken more design work and I'm probably 2/3 though this conversion. I hope to finish both up next fall/winter including rudimentary chip enclosures.

I'm currently not using the Sherline for traveling. It took too long to set up for less than a week or so in one place, and chip control became a real problem. But, the Sherline lathe convinced me a CNC lathe was a useful addition.

Longer term we still plan to travel, probably 4-5 months a year. Winter in Brenda (Quatzsite) and travel summer with a few months in Prescott when everyone else is traveling (crowded). It's a simple plan and could change. We hope to head out mid to late April, real soon now, for the summer. (where shop time is zero and Internet is scarce)

Did you and your grandson Lewis complete the Stirling engine? I still have parts for mine and plan it to be the first project when the small shop is up and running. I need to complete that build thread. Hopefully next winter.

Thanks for asking. I hope I'm not eating up too much space on a very nice build thread.

Stay safe.

Hugh, I have lost touch with your movements. Are you still traveling and exploring?