Streamlined gasoline-ICE microcar/tadpole trikes

.No reciprocating mass and total friction is likely lower at small diameters.

Why would you think that? It still needs apex seals and face seals, and displacement falls more than surfaces/seal area as size decreases, just like a small Otto cycle engine.

No amount of fiddling makes a rotary as "fuel efficient" (very loosely used here) as an Otto engine.
 
The 5 horsepower or more is wanted in the case I want to cruise at 90 mph on flat ground, or need to briefly go faster so I can get away from the cops(this amount of power which will greatly extend my usable range and reduce my immediate need to charge). I've already used the coroplast velo in a street takeover with some Dodge Chargers. That was fun. Then with that much power, I can run the engine intermittently for what would be more typical usage cases, like riding all day long hundreds of miles into the boonies and not being able to find an outlet to charge, and only needing to deal with the engine noise/vibration for part of the time.

Good points. But it does make things heavier and bulkier.

The 90 mph and 'get away from the cops' makes it sound like you are thinking parallel hybrid where the 5hp would ADD to the electric power when required?

That means thick/er chains and preferably a gearbox? Although the motor/s could take care of low end torque, allowing a direct chain drive with a sprag clutch?
With 'regen' that negates the need for an extra electric generator/motor.
Perhaps a stand to lift the velo's drive wheel off the ground for stationary charging?

As it's open; the size difference Between a rotary and = good ol Piston Powa! :)
0027cc_comparison.jpg

:)

I'm thinking that; bolt 2 together and you have 5.6hp and still way smaller and lighter.
Pity it's vapourware.
Start a: Message these guys saying you want 1! 2! :D
With the fuel/air charge sucked between the fins over the hot combustion area/part of the housing..!


Old school and a 350w hoverboard motor:
The maths says the engine can turn both motors.
It also says: Put the rotors together and wind them as 1 long rotor.
That's still only 700w and the engine can take a bit more with a better matched motor/generator.
[MEDIA]
 
Last edited:
Why would you think that? It still needs apex seals and face seals, and displacement falls more than surfaces/seal area as size decreases, just like a small Otto cycle engine.

No amount of fiddling makes a rotary as "fuel efficient" (very loosely used here) as an Otto engine.

  • What I meant was;
    • No (high friction) reciprocating mass losses.
    • Total rotary engine friction is likely lower at small diameters than that of a piston engine of equal power.
    Thx for catching that.
 
Honda GX-31 4-stroke mated to a generator. That's a bike rack under it.

This never got actually built, but I think it would work.

View attachment 364831

I just cant move away from rotaries it seems.
They may only last 15min? but the power to weight and size! :)

Displacement: 2.6cc*2
Carburetor: single/double
Compression ratio: 8.2: 1
Rotating speed: 2200-18500rpm
Power: 1.46ps @18000rpm Edit: = 1.44hp from 415 grams!
Engine Weight: 415g
Cooling: Water-cooled
 
Last edited:
A change of subject at last! :)
I believe a DIY Linear Generator is (easily?) possible:
(unbeatable efficiency and size? And you can run it at 1 'rpm' if you like)

(Should I copy/paste the thread here rather, or is it OK left just on Ecomodder?)
 
Last edited:
Why would you think that? It still needs apex seals and face seals, and displacement falls more than surfaces/seal area as size decreases, just like a small Otto cycle engine.

No amount of fiddling makes a rotary as "fuel efficient" (very loosely used here) as an Otto engine.

I replied:

What I meant was;
  • No (high friction) reciprocating mass losses.
  • Total rotary engine friction is likely lower at small diameters than that of a piston engine of equal power.
Thx for catching that.

Most people would say: "...a pleasure and..." carry on the discussing about Fuel Efficiency and reliability at small size.
I'd like that as you seem to have as much knowledge on the subject as you do on starting arguments!? :)
 
I Most people would say: "...a pleasure and..." carry on the discussing about Fuel Efficiency and reliability at small size.

That Wankel engines are thirsty is common knowledge. He's what the great Goo has to say about it:

Factors affecting Wankel engine efficiency
    • Combustion chamber
      The combustion chamber is long, thin, and moving, which leads to slow and incomplete combustion.
  • Compression ratio
    Wankel engines have a low compression ratio, typically around 9:1.

  • Fuel and air mixture
    The fuel and air mixture is poorly quenched, which leads to unburnt hydrocarbons in the exhaust.

  • Surface area
    The Wankel engine has a large surface area, which contributes to poor thermodynamics.

All these except compression ratio become inherently worse as internal combustion engines decrease in size, regardless of type, due to square/cube effects. Seal length (therefore friction) scales linearly with size, surface area (therefore heat loss) scales with the square, but displacement scales as the cube. So energy losses hold up much much better than power as you scale down.
 
That Wankel engines are thirsty is common knowledge. He's what the great Goo has to say about it:



All these except compression ratio become inherently worse as internal combustion engines decrease in size, regardless of type, due to square/cube effects. Seal length (therefore friction) scales linearly with size, surface area (therefore heat loss) scales with the square, but displacement scales as the cube. So energy losses hold up much much better than power as you scale down.

Thirsty:

AI Overview[​
When a fuel and air mixture is "poorly quenched," it means the combustion process is not effectively stopped or cooled down quickly enough, resulting in unburned hydrocarbon molecules escaping into the exhaust system, essentially meaning that some of the fuel did not fully combust and is released as pollutants​

That's not good!
I have some ideas on that I'm keeping under my hat for now. :)

I suspect that the power stroke in the same area of casing all the time results in overheating issues.
But doesn't in 2-strokes..? Added frictional heat from the apex seal? Surface Area.
Running Rich is a known and used method of cooling Turbo'd etc engines.

(The way to properly do it is water injection that has a higher specific heat, and costs nothing.
Problem is water injection slows combustion, so the advantages in a piston engine are from increasing compression)

Spit balling:
But what happens if you run the air-fuel mixture through between the cooling fins over the hot area?
Evaporative cooling and evaporated, much faster burning charge..?
Aha!
Air-Cooled Rotary Engine: Compact Power for UAVs and Compact Systems

Also hotter intake area of the case, but not a hotter compression area.
Together that's a faster burning power stroke, cooler combustion area, a better heat spread and less uneven expansion.
But water cooling the the engine is still better IMHO.

As evaporation drops air temperatures sub ambient; perhaps a small post radiator, radiator in the intake after the fueling.
ie: Coolant cooled normally then some more with a sub ambient gas..?

Then Pyrolise the fuel completely with Exhaust heat and try for some steam reformation and/or Water-Gas Shift with catalytic surfaces to get a bit of Hydrogen..? (40% better fuel efficiency IIRC. Burn anything. Used in old tractors and such)

I want rotaries to work damn it!? :)

Surface Area to volume:
Hmmm...
Doubling all the dimensions of a cylinder increases its volume by 8X.
Its surface area by 4X

Inversely:
Halving all the dimensions of a cylinder decreases its volume by 8X.
Its surface area by 4X

So 8x less volume for 4X less surface means volume drops off faster than surface area, which means more surface area losing heat per cc...

So energy losses don't hold up with decreasing capacity...
 
Erika! :) I have found Toecutter's perfect diesel engine!
Not only is it small and quiet, it comes with a built in wheel rim! :D


Seriously; these old style engines have a lot going for them:
Surprising as it may be, they tend to run on the smell of an oil rag, due to low volumetric losses and low friction.
You can't beat them for accessibility and ease of repair.

They really are very quiet and easy on the ear when not banging on a table!
Here's another video: (no muffler!)

The 1st one is only 16cc and would have trouble lighting a LED bulb I think, but if you're looking for a constant slow and steady charge for a battery, something like that might be easily lightened up , put in a quiet case/sump and auto lubed.

The conrod to a rear wheel idea saves all the flywheel weight if you just want to cruise and charge on a quite pleasant sounding engine..?

(Cooling in this case is by boil-off btw.
Filling the tank was by float valve in the top of the tank in the larger stationary engines.
Hot water for home use came from the same tank, back in my youth on the farm)
 
For my application, power to weight ratio is important. I wouldn't need more than about 5 horsepower continuous though, and the smaller of a package that can fit in, the better.

Your previous post wasn't too long. I read it and found it interesting, learning new things in the process(as well as from others' responses in this thread). I just don't have as much time to post these days.
Any thoughts on the engines posted?
It's loud, high rpm if you want light and compact.
A quiet box and Resonators ads weight and size again, unless part of the structure and is constant rpm to be effective.
Pyrolysis etc allows running any fuel, but startup/warmup is gasoline and it's constant rpm only.
 
Any thoughts on the engines posted?
It's loud, high rpm if you want light and compact.
A quiet box and Resonators ads weight and size again, unless part of the structure and is constant rpm to be effective.
Pyrolysis etc allows running any fuel, but startup/warmup is gasoline and it's constant rpm only.
I haven't had the time to give this the reply it deserves, or to thoroughly investigate the engines proposed. Although, that miniature rotary sounds amazing.
 
This post gives weight and power numbers for various engines, Including the LiquidPiston engine he's thinking about building.

"...It [LiquidPiston] also seems rather heavy, at 1.8 kg for the 69cc version...​
...I have seem online claims for Wankel engines of 5 hp at 1500 g, but probably at high revs. swept volume unspecified.​
These people seem to be now out of business. - Maybe they didn't get the Darpa Funding?​
I have a two-stroke here which is 61 cc, basic 1350 g, 5 hp rated, usable range 6000-7500 rpm​
if you add the muffler and ignition, it is still around 1500g total.​
The Saito 84 cc 4-stroke seems to have similar or better performance, and easily spins a 24x10 prop.​
its basic weight is about 3 kgs, but it looks fairly heavy construction.​
The 74cc Saito 5 cylinder is only 2.5kg basic weight, and is probably close to the 61cc two-stoke in output at the same RPM.​

I looked up my old Honda MBX 50cc water cooled and it was 7hp

Basically; If you want the best power to weight ratio you can actually buy, a 2-stroke is the way to go.
 
Yep !.. there are 2 stroke 100cc race kart engines that will output 40-50 bhp…. depending on how long you want it to last !
That's a hell of a lot of power!
:) I think we want them to last a little longer than that!

Thinking back, my Nifty Fifty, a Honda MBX 50cc made...
Power: 5.0 kw = 6.7hp at 8500rpm
Torque: 6.4Nm at 7500rpm

Which is plenty, but the engine comes with a rather bulky 6 speed gearbox.
 
I think a Thermoacoustic Stirling engine may be the answer!?
30% efficiency
Quiet...ish
And NB the similarity to a bike frame..!
ie: these things could easily be part of the tubular structure of a velo, saving weight and space.

That's just his small prototype.
I cant wait to see what he comes up with next.
(Do like etc to keep this guy funded!)
 
Ah-ha! :)

There are a number of these nowadays.

another eg. with er... non chinese price and more data:
The FD-6000W
Dimensions 312 x 288 x 206 mm
Weight 8.5 kg
Voltage 58V
Output Power 6 kW continuous
Fuel Consumption 5.8 litres/hr
Max Altitude 2000m
TBO 200 hrs

Just search
drone engine generator
One with half the power and half the mass would be perfect for what I have in mind.

OyjKbVD.jpg



I have other other proposals, including one based upon a Milan SL velomobile in my possession. But I need to do something to raise the ground clearance with that design, or the roads here will murder it.
 
Last edited:
For the model Logic listed and you wanted a lesser capable / heavy one, this is from the same series ->
Specifications:
Generator weight: 4.5kg
Voltage: 48V
Generator output: 1.8kw(continuous), 2kw(max)
RPM: 12000r/min
Size: 283x272x264mm
Fuel consumption: 620g/kw.h
Applicable UAV types: Multicopter
Recommended Max take-off Weight: 22kg
(Not exceeding the recommended take-off weight of the applicable UAV)
Service Altitude: <2000 meters
Start Method: One key starting (PWM or CAN-BUS)
Service Life: 300Hours
Maintenance Cycle: 50 Hours
Service temperature: -20 ~ 40°C
Mixture ratio: 25:1(gasoline:eek:il) (suggested #95 or above + 2T oil)

Specs seems a little less then what I listed earlier, but this has at least public pricing available.... I was a big flabbergasted these are so expensive but I guess it's a niche market.

$5,380.00 is not cheap. But I recon it's such a specialist part, to get something with close to the same efficiency is impossible as DIY even if you could probably eventually match the featureset.
 
$5,380.00 is not cheap. But I recon it's such a specialist part, to get something with close to the same efficiency is impossible as DIY even if you could probably eventually match the featureset.
Nothing specialist about it, except for maybe that it is assembled and ready to go.
Common off the shelf parts BOM:

Zenoah 32cc engine ~$400
Brushless IPM/Outrunner 10Krpm motor ~$400
FOC motor controller W/Regen ~$300 (A VESC based controller is THE swiss army knife for things like this)

Anti-vibration mounts,
Motor couplings/plates,
Raw matl for frame,
Wiring, ~$300

Matl BOM =$1400

Leaving ~$3980 for fabrication, labor, R&D, coffee, etc.


The HYBGEN generator you mentioned above uses the Zenoah G320RC 32cc engine.
 
Personally, If I were to build something like this(which I may, someday)

I would use one of Honda's GX series mini 4-stroke engines(or similar):
honda 4-sroke mini engine at DuckDuckGo

Honda Engines | Mini 4-Stroke Series

4-strokes have some advantage for land based motation:
Usually much quieter.
No 2-stroke oil mixed gas.
Usually lower emissions(see final point)
Usually longer service/lifetime intervals.

Final point, I would convert the engine to run on propane, advantages:
Massively lower (toxic) emissions, can be operated indoors/enclosed spaces with adequate ventilation, no carbon monoxide.
Lower maintenance, no gummed up carburetor from old gas.
Propane does not get 'old', absorb water from the air, rust out your fuel tank(aarrrghhh)
No liquid fuels to handle/spill/stink up your hands.
Longer engine lifetime, near zero carbon buildup, have you ever seen the innards of an engine only run on propane? they look like they just rolled off the assembly line!
You can buy dirt cheap off the shelf propane kits for slightly larger engines(I have been researching this lately for my Honda 3500w generator)

Possible disadvantage to propane:
Fuel sourcing,
If you ran your own propane cylinder, you would have to find a refill location, not that hard, but less common than gas stations.
If you ran a common 20lbs BBQ exchange cylinder, I'll bet there are more exchange locations than gas stations.

Fuel energy density:
I have heard/seen figures around 20% less than gas, don't have exact figures.
EDIT: looks like 27% less on a gal. to gal. basis, source:
Propane: An underrated fuel of the future | Fuels Fix

Just my 3cents.
 
Last edited:
I have a GX30 clone... that thing is incredibly noisy. It's a weedwacker motor, though in my case used to drive an outboard for an inflatable dinghy. It's rated 1.1hp, makes you look to the sky for the landing jumbo jet and produces equal amount of trust as my trolling motor.

Now I'm sure the original Honda's are much better.. but even GX50 47.9cc only outputs 1.47kw while weighing 3.33kg.

The options I listed earlier have a much better power to weight ratio. Not to mention you still have to add the alternator and controller.

edit: RC plane motors are the only one's which come up with comparable power/weight ratio required to DIY an alternative. Maybe Roto85FSI with 5.5hp at 3kg, but then you need to built the rest off the generator still yourself.
 
Last edited:
The ultimate would probably be some kind of thermovoltaic generator.
Something like this:
40% efficient thermovolaic cells.
A heat source from burning fuel heats up a panel that radiates infrared to a solar panel that is optimized for infrared.
Unfortunately this is still vaporware and you can’t buy one yet.

Imagine taking an old school Coleman lantern and wrapping solar cells around it. It would be similar to this.

No noise and very few moving parts to wear out.
 
Back
Top