MadModder
Gallery, Projects and General => Project Logs => Topic started by: pipemakermike on January 01, 2012, 11:14:05 AM
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I have just got the the cutting metal stage with this project. This will be my first complete engine although I have made a lot of bits for old engines over the years.
I have had the original drawing for a while but didn't feel good about it so I decided to do a 3D model (SolidWorks) to get a feel for the task. I nearly always do this for anything I plan to make. Of course I couldn't resist tinkering. I wanted to work in real metric for a start so I have been going throught the design converting it to metric and while I was at it I made a few "improvements":-
- I have added a couple of orings to the front housing and the backplate interfaces to simplify the sealing.
- I have added a ballrace to the crankshaft - it is a bit small and I may find a larger one later. - I will probably also make the engine plain bearing initially and add the bearing later once the engine is proved.
- Changed the cooling fin shape, the number of fins and the head shape.
- balanced the crankshaft.
- lengthened the bottom of the cylinder to reduce the volume of the crankcase to improve the pumping.
There may yet be other things that happen as I do the drawings.
I do have some questions, mostly general ones about the timing of these small Diesel engines
One thing in particular I find confusing on the drawings of the original engine is the reference on the timing diagram of sub piston induction. As you can see from the image4.jpg the piston skirt never opens the exhaust to allow air to be drawn into the case so I wondered if there was an intention to knotch the bottom of the piston to create sub piston induction that had not found its way onto the drawings.
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I think that I am ready to cut metal today. I have further tweaked the design.
- The shaft is now fully ballraced.
- I have lowered the bottom of the exhaust port to provide 42° of sub piston induction.
- Added an orientation pin to the crankcase to ensure that the cylinder is always the correct way round to make sure that the ports line up.
- made some of the ports into slots to improve the breathing (especially the exhaust).
I spent an evening with a friend who has designed model Diesel engines for FAI teamracing and incoporated some of his suggestions.
- Lightened the piston
- Added pads to the gudgon pin (probably PTFE or bronze)
(http://madmodder.net/index.php?action=dlattach;topic=6551.0;attach=7357)
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Evening Mike,
What sort of equipment are you using to make this engine?
Nick
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Hey Mike!
I will be watching this one.
You getting technical on your tweaks. Sounds like it is going to be fun. Have you started cutting metal yet?
Eric
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Yes having spent my life designing stuff professionally I can't resist "improving" designs also, I have been using model Diesels in competition and sport flying for 55 years and this has coloured my thinking. I have a VMC vertical milling machine, a much loved Myford ML7 bought new in 1974 and a Chester Cub that, despite having bought it new in 2003 I am only just comissioning and solving all the faults that it was delivered with.
I started cutting metal tonight but just roughing out a few lumps of ally. most of today has been spent fitting a collet chuck to the Cub. Tomorrow I should get some parts made for the engine.
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The crankcase is well advanced needing only the choke hole and the cylinder orientation pin hole. The front housing is roughed out and I am awaiting the delivery of the ballraces.
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Nice build, I will be looking forward for this engine :clap: :clap:
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Hi Mike
This looks like its going to be an interesting build :headbang:
Rob
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Good day today finished one crankcase, turned the outside of 2 cylinders, made 2 backplates and machined up a blank for a second crankcase.
It looks as though I will be making 2 of these engines. I am planning to do one front housing with a plain bearing and one with ballraces so I thought that I might as well make 2 complete engines
(http://madmodder.net/index.php?action=dlattach;topic=6551.0;attach=7379)
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I have now finished the 2 engines. In the end I fitted ballraces to both engines and they feel lovely to flick. I have run both of them and they start and run very easily.