Model Engine Maker

The Showcase => Engines => Topic started by: Craig DeShong on September 17, 2018, 10:04:05 PM

Title: Root and Vandervoort Vertical
Post by: Craig DeShong on September 17, 2018, 10:04:05 PM
This is a 5/16th scale model of a 4 HP Root and Vandervoort vertical engine.  The castings and drawings are distributed by Rocky's models.  A partial build log appears in the 'From Kits/Castings" section of this site.

I've been fooling with this engine for a while since the build log was completed.  I had a few issues in getting it to run well.  Among those were increasing the diameter of the venturi in the mixer and fiddling and fiddling, (and did I say fiddling) with the timing of the exhaust/igniter.  I finally found a setting where it would fire around 15 degrees before TDC, and that gave it a huge increase in power, and allowed it to hit once (usually) and coast. 

At this point it starts promptly (remember to pump the fuel pump a few times to lift gas into the mixer) and runs fairly well.

Title: Re: Root and Vandervoort Vertical
Post by: b.lindsey on September 17, 2018, 10:34:54 PM
Very nice Craig and it really sounds good now that you've got the timing sorted out. Well done and beautifully finished model!!

Title: Re: Root and Vandervoort Vertical
Post by: Jasonb on September 18, 2018, 06:55:25 AM
That's running well with a good amount of time between hits.

What diameter did you increase the venturi too as I need to get back to fiddling with the one I made though the guy that started building it did muck up the carb a bit.
Title: Re: Root and Vandervoort Vertical
Post by: zeeprogrammer on September 18, 2018, 01:52:04 PM
Beautifully done and I agree the sound is great.  :ThumbsUp:
Title: Re: Root and Vandervoort Vertical
Post by: Tennessee Whiskey on September 18, 2018, 05:20:01 PM
Craig, this popped up on my "recommended for you" videos on YouTube. Really nice and the sound is awesome :ThumbsUp: :ThumbsUp:

Title: Re: Root and Vandervoort Vertical
Post by: Craig DeShong on September 18, 2018, 10:32:56 PM
Thanks for all the kind comments.


I communicated with Rocky regarding the venturi.  He stated that his engine runs well with the venturi as stated in the drawings.  He also stated that several folks had contacted him about this and they got their engines running well only after they had increased the venturi size.  He didnít have a measurement.

You have to realize that the engine is drawing ALL the fuel/air it runs on through the 1/16th inch venturi.  To me this is insanely small.  I was tempted to drill it out MUCH larger, but the outer size of the venturi wall is 3/16th inch.  I started with drilling the venturi out with as 1/8th inch drill.  This seems to work well, and the engine isnít ďgaspingĒ as it was with the 1/16th inch venturi.  This is what I stayed with.

I also increased the size of the fuel pump barrel to ľ inch.  This might not be necessary since I was having check valve problems concurrent with this.  Itís imperative that the check valves function or the gas just runs back down into the pump and the mixer starves out.  I took the return fuel line and routed it to a pan on the table and verified that I got a steady stream of fuel running out the return line when I turned the engine over.

My fuel pump was seeping fuel out the top of the pump alongside the plunger and the fuel was collecting on the base on which the engine is mounted.  I didnít like this so I used a 3/8th inch drill to cut a lip into the top of the pump.  I placed an o-ring on the plunger and let the spring sit on top of the o-ring; seating it in the lip Iíd cut.  This seems to have stopped the gas leaking out of the pump.   

Finally, I advanced the spark to about 15 degrees before TDC.  To do this I had to move the cam gear forward one tooth and now the exhaust valve timing for open/close isnít exactly where Iíd like it to be, but with the spark at TDC the engine couldnít develop enough power to kick in the lock-out and I couldnít advance the spark any more with the igniter trip mechanism as I made it.  At 15 degrees TDC it hits hard enough to spin up to speed when it hits and will get the centrifugal pump to pump.

One other thing I did was to put a check valve in the water line at the exit to the pump.  This keeps the water from flowing back into the pump when the RPMís spin down.

If I remember to pump the fuel pump a few strokes so that there is fuel in the mixer, the engine starts without too much fooling with it.

Hope this helps you get your running.   
Title: Re: Root and Vandervoort Vertical
Post by: Dave Otto on September 18, 2018, 11:31:44 PM
Very nice Craig, she runs perfectly!