TVS Vacuum Engine

[LegoLord1880]

I like OHV vacuum engines as much as the next guy, but they have more than their fare share of issues. Of course I mean the intake valve. It needs to have a hard enough spring to not get sucked open by the vacuum, but has to have the right rocker ratio and valve clearance for the engine to run well. The first work-around I've seen is to use butterfly pistons to break the seal and take in fresh air, but these also have problems. One is the piston itself. It tends to get caught on the seams between brick layers. On top of this, it only really works well with 4x4 or 6x4 pistons, and crankarms with a 2 stud radius. With these issues in mind, I went ahead and made my own fix to these problems.

My new engine design is basically a classic SVS engine with a head. It uses a modified SVS valve on the side of the block to let in fresh air as the piston goes down. Then, the slide valve closes, and the poppet valve in the head opens for the power stroke. Because it uses two kinds of valves, my working name for it is Tandem Valve System, or TVS. 

It has all the benefits of SVS engines: It works with essentially any bore or stroke size, gets decent RPM's and torque, can be turbocharged or supercharged, and can even run on positive pressure, unlike other OHV engines. It also gets around some SVS limitations, like the manifold. The TVS engine also has the OHV benefits of realism, good sound, and the ability to make it into a four stroke. This engine ended up not even needing a flywheel, but I still used one anyway.

That's not all folks! I mentioned on another thread how my vacuum engines have Water Injection, where water is pumped through the intake for extra lubrication and cooling to enhance the performance. My new TVS engine has a CARBURETOR to deliver a mist of water to the intake manifold to achieve the same effect. Here's how it works: I use a pneumatic pump submerged in water to get the water into a hose. In the carb, the pneumatic hose squirts water into the "venturi", into a minifigure spear mounted in a half-pin, which functions as the jet. The blast of water makes a fine mist, and the "richness" can be adjusted by moving the jet needle in or out. Then, intake vacuum draws the mist into the cylinders for lubrication. The carburetor also has a single butterfly valve made from a 4x3 plate which functions as the choke. When the choke is closed, it blocks some airflow and slows the engine down, while enrichening the mist. it all works quite well, and surprisingly makes a noticeable difference to running the engine without the carburetor.

Now lets talk specifics: This particular engine is an Inline 2 with 6x6 pistons and a 3 stud stroke radius, for a displacement of 184.32cc, or 11.24 cubic inches. During a dyno test, it made 28 Studpower, or 0.0028 Horsepower. During the test, it made 0.03125 ft/lb of torque at 500 RPM, but peak torque when stalled came out as 0.0625 ft/lb, and a maximum speed of 2200 RPM (Not simultaneously).

I think this engine design has alot of potential, and seeing as this is only the second prototype, there will definitely be a few issues to sort out. I hope you guys like it!

Here is a link to where I have pictures posted on Bricksafe: https://bricksafe.com/pages/LegoLord1880/vvt-vacuum-engine/technic-starter-motor-prototype/kohler-k241-vacuum-engine-model/3-valve-vacuum-engine/tvs-vacuum-engine      I also hope to have a video of the engine running and the carburetor in action soon :]

 

 

[2GodBDGlory]

I love that you're posting this stuff on Eurobricks! This whole Lego vacuum engine thing is quite foreign to me, and all the specialized terminology you're using just goes to show that it really is a whole world that I'm just getting a glimpse of through your posts!

Your first sentence "I like OHV vacuum engines as much as the next guy" kind of cracked me up, just thinking about how virtually nobody has an opinion on vacuum engines, much less specifically OHV ones!

It's super fun to see this stuff!

[engine1ear]

That is a very cool design with a very well thought out justification. Everything you said in your justification made sense with the most novel to me being the manifold issue that SVS engines have. I never made a multicylinder SVS so I never thought about how there is a pathway from vacuum hose to atmosphere at all times as soon as you introduce a second cylinder. That alone was worth taking a closer look at this interesting engine, not to mention the carburetor! Very cool!

Quote

virtually nobody has an opinion on vacuum engines

Especially here on EuroBricks! The LEGO vacuum engine builders are mostly on YouTube, TikTok, and Discord, and are mostly teenagers so it's really cool to see your openness and interest :D

[LegoLord1880]

Yeah, the manifold is a pretty big problem with SVS engines. You've got two options: you can either make the engine in banks of 2 cylinders and have manifolds between, or the more popular option is to put them all in one bank. The first option is only good for an I2 or U2, because you get the absolute least amount of manifold, but the engine is super long. If you want say, an I4, you have to make 2 of these units and plumb them together with a THIRD manifold! The second option isn't much better. You just make one huge manifold connecting all the valves. You either get good air volume (by making the manifold out of 4x6 plates) or good airflow(with 2x6 plates), and you have to choose which to shoot for. It's REALLY hard to get good volume or good flow anyway, because you're forced to make the interior of the manifold just 1 brick tall, otherwise it screws up the valve timing. With all this in mind, you also can't make the manifold too big, or you use up all your vacuum's capacity to suck air from it and not the cylinders.

That's one major issue my TVS engine fixes. The external manifold serves only to hold the carburetor and direct intake air. All the vacuum valves are in the head, so I used the interior of the head as a manifold.