This winter project is to modify a gasoline engine to run on compressed air. The only reason I chose to do this is because I believe I can. I pondered my approach regarding what type of engine to use - a simple two stroke or a more robust four stroke. The two stroke engine is one that I admire in that it is so simple - which would pose a problem as it lacks a lubrication system. This would force me to feed a mixture of air + oil into the engine to keep it lubricated. On the other hand, a four stroke engine has a lubrication system and valves which I could leverage for functionality. Finally, there's a two-stroke diesel engine which also has valves, but are hard to come by and expensive.
I reached out to my favorite project sourcing website - e-bay. I found a brand new Lifan (Honda copy) 50cc four stroke with semi-automatic transmission (manual shift, no clutch) for $115. Check it out here. My initial approach was to modify the camshaft and use the existing valves to coordinate intake and exhaust. However, after further research and input from a team of experts, it was concluded that the intake valve would not be sufficient to handle the amount of pressure the engine would require. A new approach was formulated.
The motor will use the existing intake and exhaust valves as "alternating" exhaust valves - one lobe on the existing cam will be re-worked to accomplish this. The existing intake port will become an exhaust port as a result. The intake will be regulated via an external valve mechanism which will feed pressurized air into the legacy combustion chamber via the spark plug hole. This valve will be driven off the cam gear due to its proximity to the intake so as to minimize any negative affects due to distance between valve and legacy combustion chamber. Engine speed will be regulated by varying the amount of pressure supplied to the intake valve. A minimum pressure will be set to support an "idle" state and a maximum pressure will be set to prevent horrible things from happening due to over-revving the itty-bitty piston. The existing lubrication system will be utilized. The current piston made in China by prison camp labor has been designated "crappy" and will be replaced with a higher quality piston.
"Progress" Updates
30 June 2009
Well, it's been a while since I have had any time to work on this project - a couple of other projects took priority (3rd floor addition to the house and the birth of my daughter, to name a couple...)
The motor is back with me but still in pieces. We'll need to do some brainstorming, but I'm thinking about sticking to the original idea of reworking the cam to act as "alternating" exhaust valves. In addition, I found a 12VDC solenoid valve with 1/2" ports capable of handling pressures up to 5.0 MPa - hopefully that will suffice to deliver the air intake. Once I get the valve I'll try to get together with the team to brainstorm.
29 January 2009
The donor bike has been delivered. Milli Grazie to Shawn for the donation and Walter for the delivery. The bike looks like a blast! As soon as I can drag it down into my workshop, I'll start taking it apart.
22 January 2009
I finally got to meet with my machinest ( his first grandson just arrived ) We seem to be on the same page as far as the valve and he is just finishing my cam grinder. We are still working on final designs. You should be shopping for gas driven 3 stage compressors. There may be used ones from the scuba tank industry. Save some money....
The
cylinders that I have in mind will take 3600 psi or more. The trick here will be
to go a mile on the smallest cylinder.
I must make more calculations. You can figure out the smallest rear sprocket and
I need to know the diamiter of the rear tire you plan on using, bigger is
better. I would't buy anything till we get all the calculations done.
Regards
Pete
14 January 2009
THE EAGLE HAS LANDED...
"Pete has your baby as we speek."
8 January 2009
Greetings and salutations! I hope
everyone enjoyed the holiday season and wish all the best for the New Year.
I am pleased to report that Walter and I have successfully "cracked the case" -
not literally, thank goodness (unlike the unfortunate itty-bitty piston
skirt...) What an overwhelming sense of accomplishment to finally be able to
complete an hour's worth of work with only two trips to
JDS and all within a month's time!
It took several blows of the hammer, but we finally got the cases apart and
gutted. Walter dutifully photographed, bagged and labeled every part that was
removed. We pretty much gutted the entire engine with the exception of the
crank assembly and the cam chain
tension adjusting mechanism which didn't seem to be in the way of
anything. We were only unable to make up a name for a single bag of parts, so
we left it labeled, "I don’t know." I'm sure a
professional will be able to identify
it at a glance.
Two boxes will be delivered to JDS tomorrow morning – one with the engine
labeled, "outside" and a smaller box of bagged parts and gaskets labeled,
"insides."
For our next feat, I would like to get the donor bike and begin breaking it
down. I would like to remove whatever paint/decals are currently on it and
refinish it. I am partial to heavy metal flake, but also like a lot of chrome.
Anyway, I am open to suggestions.
UPDATE:
Mike has weighed-in and offered the following suggestion:
"HEAVY METAL FLAKE!!!!!!!!!!"
18 December 2008
Detective Kudron and I cracked the case! Literally. Now I know the objective was to split the case, but we did get as far as cracking it without breaking anything. We were once again befuddled by a fastener - this time a nut requiring a tool that probably costs more than the whole engine did to remove.
Of course, in true backyard mechanic fashion, we had a go at it. We tried heating the nut; we tried hitting it with a hammer; at one point we used a strap wrench, needle nose pliers and a pipe wrench. Needless to say, not only did we not break the nut loose, we broke the needle nose pliers. Once again we need to turn to the professionals for assistance...
"JDS - please help! We are not worthy!"
- W. Kudron
13 December 2008
Sean (see also: Professionals) removed the nut and stator in less than 30 seconds................
We are humbled.
11 December 2008
We were off to a good start at the beginning of the evening. Walt - a master
"bagger and tagger" - diligently catalogued and photographed every nut, bolt,
gasket, cover, o-ring and dowel
pin we took off. Starting at the top (of both the engine and a fresh
bottle of Evan Williams) we
carefully worked our way down (both the bottle and engine). Off came the head;
next came the cylinder. Easy as pie. Then the trouble began...
Now that the top end was off, we turned our attention to the bottom end – first,
the charging system. Typical - stator affixed to the case, rotor affixed to the
crank shaft, 14mm nut
holding it together. First question of the night – is that nut holding the
rotor to the crank shaft a reverse thread? We contemplated, debated, imbibed
and concluded nothing. Call in the Copper Smith! Enlightenment was bestowed
upon us – standard thread. Now, all we needed to do was figure out how to lock
that engine to break that nut loose.
Using the best tools available – a ˝”
breaker bar which more than
likely saw its share of action in WWII; and various scraps of wood – we had at
it. We tried everything - locking the gears, blocking the piston, standing on
one leg, crying, begging and pleading.
In the end, the only thing we managed to break was the skirt on the itty bitty
piston. Both sides. Hopefully that’s the only thing we broke…
Walt, finally admitting defeat, looked at me through glazed eyes and said, “We
got to get this over to JDS…”
It’s clear this made in China by prison camp labor using antique tools engine is
beyond our skills and abilities. It’s time to call in the
professionals.
Project Resources