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check out this small engine im building!

For my last semester in high school im taking a metal shop (yeah i'm 18 if you guys didn't know or care) and since i took one in freshman year, i wanted to build something cool. Now most other students made some dumb things like BBQ pits and crap but i wanted to try something a little more difficult. Like build an engine. yeah an engine. not assembling or putting an engine together but making and engine from scratch...oh yeah with only simple power and hand tools (no lathes, molds, computer controlled crap either) MIG welders, Demel, and of course grinders are allowed
we have a crappy TIG but i'm not good enough with that.

so being the most skilled welder (my teacher said i taught him a few things as well) my teacher was only a little leary when i told him what I wanted to make. so i set out with my main rule or using only simple tools and so far it's gone well. luckily i found a pipe that fit inside another with very close tolerances (less than 1/64th") so off i went and using only flat plate, soild rod, tubing, nuts and bolts, and bronze bushings. now i considered making my own simple nuts and bolts, carb, ignition (coil and battery made of lemons) but i'd run out of time.
so heres some pictures of it:

Now all this will be mounted on a metal platform the has the battery, coil, and fuel tank( i still don't have a flywheel though, any ideas for a 1.5-2lbs wheel thats less that 4" dia. with a 1/2" center?)

Heres a small(i don't know why) exploded view the show all the simple parts of this 2 stroke beauty, the case comes apart in 2 pieces for assembly and repair, and the cylinder will be detachable
http://i81.photobucket.com/albums/j2...plodedview.jpg

the heads not bolted on tight and the head gasket isn't in :wink:

http://i81.photobucket.com/albums/j2...ngineleft2.jpg

the port on top is the exhasut port but i'll probably make it smaller for more exhaust velocity and make a simple muffler, the smaller port that goes into the case is the intake port

http://i81.photobucket.com/albums/j2...enginetop2.jpg

this is the piston with a ring in it, the groove was painstakingly cut on a power bandsaw and had to be done twice cause the first was too sloppy
http://i81.photobucket.com/albums/j2...c15/piston.jpg
Heres the ring and carb from a Thunder Tiger model airplane engine
http://i81.photobucket.com/albums/j2...arbandring.jpg

heres the engine mine is modeled after (same stroke, bore, carb, etc) however mine will run on gas not nitro it's 15ccs and rated at 1.5 hp
http://i81.photobucket.com/albums/j2...5/supg0235.jpg

So what do you think? i know it looks if'y but we'll see how and if it runs.

so give me any questions, comments, tips, ideas or whatever you have for me!

Vwdmc16

So since your modeling your motor after a nitro methanal/ethanal glow plug ignition design... how are you planing on ignighting gas? with a spark plug it looks like? how are you controling the spark?
and is this going to be a 2 or 4 cycle engine? (you have no valvetrain... so im assuming 2)

im interested to see it done!

Jonathan

Hello,

This is true, the glow engine you are copying uses a glow plug with a thin wire element in it that glows, For your spark plug to work it will have to fire continually, or at the right moment. I suppose you could put a "cam" or a bead of weld somewhere on the flywheel that triggers a microswitch at the right place wich grounds a coil to fire the spark.

Anyways that looks like a fun project, wish i had the time :(

Bry

you guys are exactly correct, it its a 2 stroke (i couldn't make valve train parts that small)
the igniton is a conventional make and break with a 12v coil from an old suzuki moped and a lawnmower 12v battery, i'll use an old points from my VW :D and i will have a dimple on the flywheel as soon as i find a sutable one

Any ideas on a flywheel?

hmmmm.....ok
You could use a VW alternator pully lol! might not be heavy enough? the heavier it is the easier it will be to keep it running. but i dont think you want it to heavy or starting the cycle could be harder.

hey i got an old generator pulley, that may work

however there is a point where the weight is too much and the heavy weight will dampen the torque impulse and the motor will stall so maybe a 1/2 -3/4lb flywheel would be best

Research the weight of the Thundertiger (or any engine of the same displacment) flywheel. That may give you a direction on how much weight and diamater you may need... only thing is that your using all steel (heavy) internal componets, and i think that thunder tiger (as with most engines) use mostly aluminum internal componets (lightweight) so that may also change things with your selection.

I use to do a lot of 1/8 scale nitro on and off road racing when i was growing up. and the flywheel weight changes a lot of things... but i think for your purpose its not super critical as your not going to be using the motor for any real locomotion of an object?

well i've been hard at work on the motor but it is still slow going, i've got less than 10 days of class day to finish it if i want to try to start it before im out of school. anywho, i've made some solid mounts for the cylinder to fix on to the case but it's still kind hacka and really poor fitting, oh well thats what liquid gasket is for! :)

i'd refine it more if i had time but i don't. for a flywheel i went back to an idea i had before, cut a thick disc of steel out of some 2" solid rod we have at the shop, i cut a few thicknesses to experiment with the flywheel wheigh, overal that will look good. the tricky part is getting the hole dead on the center, which it isn't, so yeah it's gonna vibrate bad. i still haven't decided on how to secure it to a 1/2" solid rod which is the crank size, a woodruff key, pins, threaded shaft and nuts? i don't know. also i found a perfectly sized pip for the intake moanifold to hold the cab and reed valve, that's another tricky part

well i've no pics today bu maybe on friday

cheers

Just a question (non related to any info on how to build/improve your design, sorry)... Getting this little engine of yours running before your time is out..., is that a personal goal or a requirement of your project to score points? Personally, if I was a teacher, I would give some serious credit for effort/thought/execution of idea etc. That is what it is all about no? Thinking out of the box etc.... Or am I missing the whole point of school/projects? :confused:

Either way, some may say that you are not doing anything special(by modeling it after an existing engine), but I say top job!! :agree: Keep up the good work, and maybe we can see it running, even if you run/ran out of time!????

Quote:

Originally Posted by vwdmc16

the tricky part is getting the hole dead on the center, which it isn't, so yeah it's gonna vibrate bad.

Bet the metalshop has a lathe....
Thats the tool to use to get a hole dead center ;)

Sam C

sorry no we have no lathe, damn, my old highschool's shop did some 30yr old rusty ones but a lathe none the less.

so this isn't for extra credit or a grade at all, but i will be making a 100% in there so woo hoo. most kids build simple stuff like BBQs, the first semester, we learned the tools and showed our skills on various welds and fabrications. i was the first finshed by a month. and with the highest grades. but all we do the second 1/2 is build what ever we want and pay for the metal we use. it's pretty cool