Vega V twin Aero engine

[creast]

I have not had much time to progress far with this project but today I had a go at making the cams. In the original article the cams were pretty much hand filed and I really didn't fancy that. I pondered on making a cam grinder but then decided to go the eccentric turning route as per the Edgar T Westbury method.
My turning fixture was hurriedly made but at least I knew the offset was ok despite hacksawing the clamp details!
This process is very slow, turn a bit and then rotate the cam 5 degrees or so each step. The cam blank pair is Loctited to a temporary shaft and will come off when I finally heat treat them.
All in all it took 1.1/2 hours to turn the two cam part.

 

[creast]

Progress is slow.
I have finished both cams and heat treated them. After making a trial test piece for the gear meshing I machined the timing case centres accordingly but found the gears binding badly. Perhaps the cheap gear was a bad idea as they were obviously not running true. I re-bored and bushed them and even re-bushed the pinion shaft bore. Looking at the teeth under a x20 Lupe I could see the teeth were not that great.
However, I have left it running in my lathe and hopefully the tight spot will ease off otherwise its start again and I have little enough time or patience.. LOL!

 

[Swifty]

Others have used a little lapping paste on the gears to run them in, reports are that it works well.

Paul.

 

[creast]

Thanks Swifty. I will give it a go.

 

[petertha]

.. Perhaps the cheap gear was a bad idea as they were obviously not running true. I re-bored and bushed them

May I ask what sort of commercial gears they were? Reason: I've seen some what I think are RC car type gears down in low tooth count (metric) sizes, but have no idea if they would be suitable or not.

 

[creast]

The gears were purchased from Rapid Electronics,
http://www.rapidonline.com/FFSearchResults.aspx?query=48dp gear&filterSearchScope=1
and they are ModelCraft brand. They were the cheapest I could find that would suit at only a few £ each, others would have cost around £40 a set and I thought that a bit steep. I do not have the facilities to cut my own otherwise I probably would have a go. The teeth don't look that smooth under magnification but I think I should have held on the OD originally rather than the boss to bore them out. I did go back that route to correct them but there is still a slight tight spot.

 

[SixSixSevenSeven]

On the subject of 2 strokes from the previous page. I've just been watching a video of a cutaway V-twin, [ame]https://www.youtube.com/watch?v=_-PxRpPgHAM[/ame]
With the 2 pistons sharing 1 crankpin they do move almost simultaneously, now I'm no expert but it does look like on a sub 90 degree V-twin like this at least you could probably use the crankcase to charge the cylinders as is. Of course on a 180/flat then it becomes impossible to use the crankcase and anywhere inbetween will probably just prove damn difficult. But on the arrangement I linked, my belief is that it would be possible.
Of course you do also get setups like the old detroit diesels, fuel/air mix never even touches the crankcase and is supercharged instead, intake port in the cylinder is still in the conventional 2 stroke location, exhaust port is poppet valved from overhead cams (and with 4 valves per cylinder on some models), full pressurised oil system and the full malarkey. Defeats the purpose of 2 strokes being more mechanically simple though.

The Aaen performance v4 may well be 2 2stroke v twins as I describe back to back (and is poppet valve exhaust with fuel injection too)



I'd take anything I say with a pinch of salt though when my workshop consists of a bed and my tool collection consists of a few screwdrivers. Hands on engine experience, does driving a car count? Probably not, don't really touch the engine except to check the oil level and bash the fuses back in after they get shaken loose (seriously, who at opel thought that sticking the fuse box above the front left wheel is a good idea? Hit a speed bump, there goes another fuse, never buying another vauxhall, too many problems).

I just love reading these projects and watching the engines come alive, slowly got a .txt full of notes coming together though for in a decade or so when I finally get around to having the tooling to try myself.
Excellent work, looking forward to seeing the result.

 

[creast]

Hi Six,
Hope you don't mind me shortening your nick
Yes it does look feasible for that angle to work, its almost like its one big single really. Nice vid!
As for the Vauxhall, I have one, a Corsa, and its not the only make to put fuses in a stupid place either. Try some of the french varieties, they put them all over the place!
Thanks for the useful info!

 

[edholly]

I know this thread is about the build of a wonderful engine and maybe one shouldn't "but in" - but thought I'd add here that I have built two .. 60 degree Vee twin 2 strokes and have proved that although it looks like it will work in theory as a big single, fact is that it does not. The lead cylinder gets the lion's share of the crankcase mixture leaving the following cylinder with almost nothing. If you want to follow the build of the last engine see ... http://www.homemodelenginemachinist.com/showthread.php?t=22760&page=6 ... Ed

Probably the most relevent sentence from around 3 months work ...

As for the Vee Twin itself, in reflection a lot of fun work to get to the point where I have to class the design as something that won't work as a simple 2 stroke. I really enjoyed the exercise however and have a couple of nice motors to look at and occasionally run, but the built in inefficiencies mean that they struggle to be as powerful as the single cylinder from which they are derived.

 

[johnny1320]

Harley is 45deg it might work. For best results you need separate crankcase, outboard motors use a ring on the crankshaft to seal the adjoining cylinders.

 

[johnny1320]

Edholly built a 60deg diesel two stroke on this forum, he found abandoned the design for a inline twin with better results.

 

[creast]

I know this thread is about the build of a wonderful engine and maybe one shouldn't "but in" - but thought I'd add here that I have built two .. 60 degree Vee twin 2 strokes and have proved that although it looks like it will work in theory as a big single, fact is that it does not.

Thanks for the 'real data' Ed,
It did occur to me overnight that the only chance for the 45 degree to work as a 2 stroke is in fact when its working like a big single and as you point out it never really is as there is a phase difference. Anyway, you might as well just make a big single anyway. Thanks for confirming my suspicions and I will get back to making the valves for my 4-stroke
Rich

 

[creast]

Today I started on the tappets.
The article called for M.S case hardened but I chose to use silver steel (drill rod) as its an easier process to harden/temper.
The drawing also suggested making one piece which is a bit tricky for my skills in trying to hold tolerance and finish over quite a long flimsy shank so I decided to fabricate.
The followers were made from 01 tool steel and subsequently hardened.
The shafts were ground stock 2.5mm rod and were turned on the ends to 2mm dia to provide location in the holes of the follower, just the tips were hardened to match.
Loctite 603 was used to secure the parts together and then the working face rubbed down on fine abrasive paper until the shaft ends blended into followers.

 

[creast]

Finished tappets

 

[creast]

Little progress to date since I have been away on vacation.
The tappet guides are now machined but I had to do a little bit of 'furtling' as we say here to get the tappets to clear the timing gears so they are now a bit thinner than planned.
The cams cannot be Loctited in position until I have sorted the pistons, cylinders and con rods etc but I have trial fitted the parts and all seems ok so far.

 

[johnny1320]

Very nice!

 

[creast]

Today I started on the conrods. After milling the rectangular shape and reaming the little ends and for the big end bushes, I decided a fixture was really required for the profile milling.
Not having CNC, I decided to rough the part out in a nibbling fashion first.

 

[creast]

Finally the roughed out ends were radiused by the somewhat 'iffy' method of rotating the part on the fixture by hand around the cutter. Care has to be taken here if you have not attempted this before since the cutter will snatch the part if it is in 'climb milling' direction. So do be careful!!
Final smoothing of the profile will be by hand. Next is to slit the bottoms for lubrication feed.

 

[creast]

Not much progress of late as I have been working on my other project, a CNC router, and I am awaiting delivery of some case hardening compound. I decided to trial fit the parts so far and identified a few parts that need a little adjustment but nothing major.

 

[johnny1320]

I can't wait to hear it run.