Author Topic: Design and build side shaft hit and miss engine from bar stock  (Read 52020 times)

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #450 on: February 22, 2019, 09:48:18 PM »
George--There is a venturi in the carb. At the inlet the bore starts out at a full 0.281" diameter. Then 1/2" into the bore it decreases to 1/4" diameter. The real kicker is that the fuel jet tube at a full .160" diameter runs all the way thru the bore crossways, creating a big obstruction for the air to flow on it's way into the carb. This by itself will create a considerable venturi on the downstream side where the hole for fuel delivery sets on the downwind side.
« Last Edit: February 22, 2019, 09:54:03 PM by Brian Rupnow »

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #451 on: February 23, 2019, 05:52:42 PM »
And this is as much carburetor as I can build today. I need some very small drills, which can only be bought at a toolshop to finish this off, and they are closed on the weekends.

Offline Art K

  • Full Member
  • ****
  • Posts: 1761
  • Madison, Wisconsin USA
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #452 on: February 23, 2019, 06:39:34 PM »
Brian,
Your side shaft engine runs very well. I'm glad to see that you got the head issues sorted out.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #453 on: February 23, 2019, 07:03:30 PM »
Thanks Art--It doesn't run as well as I might have hoped, but I'm still tweaking a few things. Of course, with a new engine like this i'm always a bit thrilled when they run at all.---Brian

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #454 on: February 23, 2019, 11:40:03 PM »
I couldn't go any farther with the carburetor today, due to a lack of miniature drills.---But--I could fit the carburetor to the cylinder head and make what changes were necessary (drill and tap two holes in cylinder head, and a small counterbore over the port hole for an o-ring). I didn't really want to machine anything today, but goodwife has a cold and didn't feel like going out. Everything fits and clears like I had anticipated, so I'm happy on that account.

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #455 on: February 25, 2019, 11:27:03 PM »
Making carburetors is not terribly difficult, just a bit time consuming. I drove across town in a blizzard today and got the 0.040" and 0.052" diameter drills I needed. Came home and carefully drilled the holes in all the right pieces, and just about to finish up here. In final assembly, I screw the needle valve top (knurled part) down onto the fuel jet until it bottoms out against the carburetor body, then back it off two full turns.  I have a selection of sewing needles from the local fabric shop, and I find one that slides all the way in until it bottoms out against an shoulder in the fuel jet. To be sure, I use the old "blow your guts out" trick on the end which the fuel line will eventually connect to. If you can't blow any air through unless you pull the needle back a bit, you have found the right size needle. I will now clip whatever part of the needle sticks out past the top of the knurled part, and solder the needle to the knurled part while everything is assembled. You will also see a tube of "seal all" laying beside the carburetor. After the parts have cooled off a bit, I unscrew the knurled part (which now has the needle attached to it), loosen off the hex nut, and put a dab of seal all on both sides of the fuel jet where it exits from the body, then quickly reassemble everything. If you don't use the seal all to seal things, the carburetor will suck air around the jet rather than sucking up fuel from the tank. Don't ask me how I know that!!

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #456 on: February 26, 2019, 12:07:20 AM »
The only other bit of carburetor wisdom that I have is this. Those lovely, shiny sewing needles have some kind of clear coat on them to prevent them from rusting while setting on the shelf. Before I try and silver solder them to the knurled part, I soak them in laquer thinners for about 5 minutes, then wipe them down with a clean dry rag and rub the area that will actually see solder on a very fine bit of sandpaper. If you don't do this, the solder will all pool up around the end of the needle but not flow onto it.

Offline crueby

  • Full Member
  • *****
  • Posts: 18559
  • Rochester NY
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #457 on: February 26, 2019, 01:01:09 AM »
Good tip on the needles, I just assumed they were chromed instead.


On the Seal-All, that is good for high temperature use? Does it say what range? Always on the lookout for that sort of goo.
 :popcorn: :popcorn: :popcorn:

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #458 on: February 26, 2019, 01:05:40 AM »
It doesn't say anything about temperature range on the package. I have used it on quite a few carburetors, and even though the carbs set right up next to a hot engine head, I've never had it fail.

Offline crueby

  • Full Member
  • *****
  • Posts: 18559
  • Rochester NY
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #459 on: February 26, 2019, 01:08:40 AM »
Just found their website, they have a data sheet that says 'Service Temperature: -40 to 150 °F (-40 to 66 °C)'

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #460 on: February 27, 2019, 10:32:08 PM »
"The best laid plans of mice and men"---I think perhaps Robby Burns may have built small engines as a hobby. My great little new carburetor that was supposed to seal tight against the head with a small o-ring---didn't!!! I played all day yesterday with no success, so today I built carburetor #4, which goes back to sealing on the 5/16" tapped thread in the cylinder head. It wasn't that bad--I got to salvage the fuel jet and the nut and needle from the o-ring carb that didn't work. Tomorrow, after the Loctite and seal all has had overnight to dry, we'll try this dance again.

Offline Art K

  • Full Member
  • ****
  • Posts: 1761
  • Madison, Wisconsin USA
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #461 on: February 28, 2019, 02:35:09 AM »
Brian,
What's another day in the scheme of things. :)
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline crueby

  • Full Member
  • *****
  • Posts: 18559
  • Rochester NY
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #462 on: February 28, 2019, 02:40:45 AM »
Watching along and learning a lot.   :popcorn: :popcorn:




With all the highs, lows, steps forward and back, have you come up with a good name for this engine. One thats clean enough to share, anyway? Great persistence!

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #463 on: March 11, 2019, 07:09:49 PM »
I'm back, after a 10 day rest from this engine. I needed a break, because it wasn't working up to it's full potential, and I had totally ran out of ideas. I have had problems right from day one with this engine, where it would fire along with the drill driving it, but then gradually die away and quit when the drill was removed. Sometimes it would run for 5 or 6 minutes, long enough to get a video of it,  and then gradually die away and quit. I tried a different cam and cam follower---no joy. I tried a couple of different carburetors---no joy. I think that today I have isolated the cause of all my heart-ache. There is something very, very fishy about either the position of the gas tank (in the base) or with that anti backflow valve which now has the 1/8" check ball in it. Today I changed back to my carburetor with a 0.156" throat and the gas tank from a different engine mounted about 1/2" below the carburetor throat, and the engine ran for 15 minutes straight and didn't offer to quit. I actually had to shut it off with the switch. This amazed me so much that I started it three or four more times, and each time I had to shut it off with the switch. I am going to see today about getting a 3/32" steel ball for the anti backflow device. Also, I have to devise a mechanism for the governor which lets me increase or decrease the pressure of the compression spring in the governor while the engine is running, so I can fine tune the hitting and missing.

Offline Brian Rupnow

  • Full Member
  • *****
  • Posts: 7575
  • Barrie, Ontario Canada
Re: Design and build side shaft hit and miss engine from bar stock
« Reply #464 on: March 11, 2019, 07:50:22 PM »
This is the exhaust cam I am using on this engine. Keep in mind that the angles are somewhat theoretical. I made no allowance for the gap of about .008" between the end of the exhaust valve stem and the part of the rocker arm that contacts it. This gap, called "valve lash" is necessary when the cam is not acting on the rocker arm, otherwise the exhaust valve would be held open and leak. The numbers say that the valve will begin to open about 40 degrees before the piston is at bottom dead center, remain open thru the full 180 degrees of piston travel as it moves from bottom dead center up to top dead center and then closes. The reality is that it begins to open about 20 degrees before bottom dead center, however it still must totally close when the piston reaches top dead center. If it remains open past top dead center, the atmospheric intake valve won't open until the exhaust valve is fully closed. I finally got around to checking the compression ratio on this engine, and it is very close to 7:1 ratio.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal