125CC sufficient (for aerodynamic custom tadpole trike)?
 

What speed/range/MPG can I expect from a 125cc/4 speed (Honda) reverse recumbent trike with a velo-like body on it?

I suppose we can estimate the weight ~500# or so, including myself, with a max weight limit of ~800#.

It's not built yet, so no, I don't have pics.

125cc 4 stroke? Lets say 11whp and 5ftlb torque?

Assuming its totally streamlined, you'd probably see around 150mpg and should be able to reach 65-70 with it.

Sweet, cuz I was hoping for 70+MPG and 55MPH tops!

Yeah, it's a 4 stroke, 4 speed. Not sure on power or torque figures, though.

I'm looking at the half tear drop profile, basically. I'd like to see a Cd of .2 or less (not likely, though, I don't think), and A of ~10-15 sq.ft. max. So assuming max figures, I want a CdA lower than 30. This should be completely doable with a tadpole, considering there is only one seat, and approx a 50" max width.

The way the engine is supposed to be setup, it won't idle at all. There's probably going to be a way to either human power the vehicle to very low speed from a stop, where the engine will take over.

If the Human Power part doesn't work out well, a recoil setup can be added to the braking system, I suppose. I want to make it so that I can continue to use the title to the original motorcycle, making it highway legal.

I have a 1975 Honda CB125 that gets 65-70mpg and tops out at around 60mph, it has one tooth larger then stock front sprocket to get the higher speed, if I want to get the top speed out of it I need to tuck my knees in and duck down.
A simple rear faring would help alot, alloy wheels would help too.

Does it get 65-70 average, or can you still get that on a long drive through the country at speed?

I've tried to hypermile on it and failed, it's hard to coast with the wet clutch and I live in an area with alot of stop signs and stop lights that are poorly timed, so when I take it on longer trips my mileage tends to stay about the same.
The change in gearing didn't seem to hurt my mileage as far as I can tell, as running wide open with the old gearing pushed the engine RPM up to just over 10,000RPM and it has a 9,500 RPM red line, so the engine was much happier and seemed to run better.

If you want to head out on the interstate you legally are going to need a 250cc engine or larger, if you want to a larger engine like that I would look at one of the fuel injected 250cc motorcycles that just came out in the past year or so, or get a 250cc vespa engine that is fuel injected.

Thanks for mentioning this as i had forgotten to.

250cc engine..... from a ninja 250!!! :thumbup:

Actually, in most places the highway minimum is 125cc.

I will still +1 the 250 motor idea, though. 800# is going to be tough enough to pull along with a 250 from a stop, (you can forget about pedaling to speed unless you're Lance Armstrong), although 500# won't be quite as bad. My Ninja and I weigh in around 450-500# loaded, and I've cargo-carried in the 700# range before.

The pedaling to speed thing is more like pedaling to 5-6MPH where the engine can run sufficiently without lugging and take over in 1st gear, enabling it to autostop when the vehicle isn't moving, and restart without using the kicker or stater.

I'm fairly certain around here that a 125 is legal on the highway, but it's still considered a moped... even if it's not legal on the highway, I'm not really concerned, because I can get just about anywhere in the state without touching an interstate highway.

Rt 15 is an artery in this area, it can get you just about anywhere up or down the state, or to another highway to get where you're going... it also takes you clean to Canadia almost, and a few states southways as well, but I don't need to touch it to get anywhere, I just end up going slower and going a few extra miles. At 100+MPG, I don't think it'll make a difference, eh?

I have to check the bike... I'm not really sure at this point if it's a 125 or not, it may be a 90. Whichever it is, I'll do what I can with it. I don't mind if it can't reliably get on the highway, but I'd like to have it able to, at least, and be able to do 55-60 carrying light cargo, like groceries or materials for a new project.

I'm thinking that I might give up the partial human powered part, though... Logistically, it's going to be difficult to package something into the already small chassis that's showing up in my head. I may look into a small DC motor and capacitor that will get me moving, to be used only after braking, but that's probably not a viable option either.

I have decided that I won't bother with electric start, though, since the motor is so small, I can use the kick starter with my hand, given the proper leverage.

100+mpg should be easy, but acceleration and gradeability, or whatever it's called, will be lacking. I think investing in a 250cc motor and a taller sprocket at some point would be a better bet in terms of an acceptable trade-off between acceleration/climbing ability and mileage. I wouldn't be surprised if you could manage better mileage and acceleration w/ a larger engine and taller gearing.

I was thinking about upgrading later if the project turns out to be "unworthy" in terms of acceptable performance, but for now, I'd just like to get it built and tested, and put some miles on it. Unfortunately, it's hard to get started with limited work area and a very disapproving home owner looking over your shoulder all the time, so the bike still sits at my Father's barn, waiting for me to rob some parts off it for my CM185T project bike, which I haven't updated in awhile, because the cost of just the piece of exhaust I need for it is prohibitive, and I'm still undecided what direction it needs to end up going.

I'm hoping that I'll have more free time by the time my Wife gets out of school, so I can actually start laying out all these things I have in my brain and getting to work on them some.

One solution to the problem of tall gears at low speed, or with big cargo in a little bike motor is the old school trail 90's. Before they had the cool sub tranny, they had two rear sprockets, and a chain with two master links. one length for big sprocket, then pop both master links and use one to put it back together on the little sprocket.

You could have one optimized for runnin' light, just you and the base weight.
The other one would be for the extra 300lbs cargo you were talking about, crappy roads, hills, passenger if you ever go that route, whatev!

my old one took about 3 seconds to change with no tools too.

Quicker than putting your passenger seat back in :-)

Great idea!

You've got to consider the fact that I'm not likely to even break 500# curb weight with a full fairing on this setup, cuz I don't even think the whole bike weighs in at like 200#, and I'm only ~150 most of the time, ~180 with my pockets full.

The max 800# limit was extremely pessimistic, and included me, my wife, possibly my kid, and groceries or something.

Given multiple solutions to a problem, my votes for the one that you can fix with a rock. heck, you could have a spare double sprocket and chain, and essentially role around with a spare sub tranny for like a 2lb penalty.

Give me reliability and ease of repair, anything else is bad engineering, and we all know what happens to naughty engineers...

I've still got a CVT pulley I could play with... too bad it's belt driven, and probably as lossy as... a jar with a hole in it.

Although I have a ~95% efficient CVT transmission design in my head that can't slip at all... Ah, but where is the money to produce it? LOL.

It seems like if you look hard enough you should be able to find a very small turbocharger that will work on a 125cc engine, the engine in it's stock form is around 12hp at 9,500rpm but it sees like a turbo would help with climbing hills and those other times when a little more power is needed while giving you the advantage of the small engine the rest of the time.

My BMW R1100RT will go 50 MPG at 80 MPH all day without even trying. I've never tried to hypermile it because it's fun to just ride it, and the riding season is short high in the mountains. It does have what I'm guessing is a pretty efficient fairing on the front. It would be interesting to experiment with a boattail. It's nice to have the combination of efficiency and power when I need it for maneuvering in traffic. You already put yourself at risk by getting out from behind the airbags and safety equipment. This bike has fuel injection, and I think that really makes a difference with all the changes in elevation I encounter on a ride. Easily between 5000 ft and 11,000 ft. Not feasible do do jetting changes in a carb. If you're in a flatter area it might be OK, but a later model bike with FI might be a better starting point if you can afford it.

How much does your R1100 weigh? How's the aero on it? about 17 HP is all that's really needed to go 70+ comfortably in most all situations.. ask Craig Vetter.

I'm not looking to build it to "have fun", in the sense that everyone else thinks. It'll be fun enough tooling around in it just knowing that my hands built it, and how many people can say that?

I've got a GL1000 sitting in the yard, if it's old enough that I can get a title for it, I'll use it for a highway trike, then I'll have one for tooling around, and one for really "getting on it", as it were.

A boat tail would help by a few MPG, but true streamlining is necessary to really see any gains, because you bike has a very high Cd. I believe I read that there was approx 80% of the engine's power wasted just to keep the bike going 80+ MPH on some bikes. Yours probably isn't that bad, I think that was for cruisers and unfaired bikes.

Don't know, but it's lighter than other smaller bikes I've had. Don't know Cd, just going by seat of the pants, but the wind goes by pretty smooth and quiet till you lift your head above the windshield, or hold your arm out.

That's cool, but if you're riding and not having fun, you're doing it wrong and ought to try something else. :D

It's not like an AeroCivic, but I don't know that the Cd is all that high, and the frontal area is pretty small compared to power at the rear wheel.

I ride recumbent bicycles and a tadpole trike, and people that have been streamlining those vehicles for years concentrate more on cleaning up behind the rider rather than in front. With your feet out in front of you, the air is dirty, but the area is small, and it's easier and more effective to put something behind you that you don't have to look over or through.

It's different on a motorcycle. You're not pushing through the air under your own power, and it's more comfortable pushing a wall of air out of the way with a plastic fairing than with your face. The challenge at the back of the bike has a lot more to do with crosswind aerodynamics and stability. Slicing through the air at Bonneville for a couple of runs is a lot different than slicing through traffic on I-70 during rush hour. I think some Kammback style touring cases could be really effective, but I think it's easier to experiment with Coroplast on low speed bicycles, or cars that have 4 wheels on the ground and more attachment points.

I'm looking forward to seeing how your vehicle develops! :thumbup:

The average street bike (that I've been looking at) has a Cd close to that of a full-size pickup.

Doesn't Cd consider area though? Because motorcycles are comparatively small it doesn't take much drag to bring the Cd figure up pretty high. The total drag though is the number to watch.

Interesting article on sportbike aerodynamics. Note that airspeed is 62mph.
Sport Rider-Testing Suzuki Hayabusa and Kawasaki ZX-12R aerodynamics in the wind tunnel

"Eight years ago, when Kawasaki engineers were designing the original replacement for the ZX-11, the prototype resulting from wind tunnel testing was almost a carbon copy of the Hayabusa--only the company figured it was too ugly to sell. And a Kawasaki engineer has confirmed the ZX-12R was in fact "neutered" to a lower top speed in its final stages of development. "

I hope we can redefine what is "ugly" and not "neuter" our motorcycles so that they can become aerodynamic.

Cd is just the co-efficient. CdA brings area into the equation, and yes, total drag is the thing that matters. "Average" is pretty subjective due to styling differences between bikes. I don't have the science handy to back me up, but I'm pretty sure that my tourer isn't as draggy as a Harley with no windshield or fairing, and I'm pretty damn positive I'm not pushing as much air as a pickup truck.

What matters to me on that vehicle is smiles-per-gallon. :D:D:D

It's a LOT less than that. My Ninja 250 hit 26hp on the dyno, and managed 104mph. It goes along fine at 7.5-8K at 70, (I don't remember the exact revs) which has about 14hp according to the chart, and accelerates rapidly when WOT is applied at that speed.

How does the 'Burg do?

Not so much anymore. I reached a peak of 81.5, restricting my speeds to 40-45 indicated, (10% optimistic is the consensus), which after modifying my weights for quicker gear changes and higher ratios in the transmission that equated to 4K. The lack of a manual clutch hindered coast down.

That engine is nice, though. LOTS of low down torque. The numbers I most often hear, as I've not had it dyno'd nor have I seen an actual chart, put the HP peak at 5.5K, and it lays down around 30 at the crank. The engine is tuned for torque, and torque it makes a'plenty.

This engine really has more to offer than the Burgman chassis and transmission has to handle, I wish I could transplant it into the Ninja frame. It could stand to be geared for 4K at 60mph in top gear, were it not connected to so lossy a transmission. I think, doing the same duty as the Ninja is currently, I could see 90mpg.

Anyway, wheel bearings, and an engine main bearing that looks bad but still goes for some reason has me side-lining the Burgman for right now. Hence why it hasn't been filled up in 2 months.

On the other hand, check out my latest tank in the Ninja, you'll really like. :D

Here's an idea that I found that's actually being produced, and comes in 50 and 150cc versions. They claim 70-80 MPG.

http://www.scootcoupe.com/images/products.jpg

I'd like to do something similar, but a little longer and more streamlined. I've decided that due to it's limited use in the area that I'll eventually be living, it should be OK with a top speed of 55 MPH, and no freeway capability. I'll probably put a moped/scooter plate on it, so that anyone I know with a driver's license can operate it.

This thing is pretty slick, too...

http://reversetrike.com/reverse-trik...hybrid75ms.jpg
http://reversetrike.com/reverse-trik...hybrid72ms.jpg

I'm thinking that I'll rigid mount the rear tire, so that I don't have to deal with a swingarm and suspension... this one doesn't need to be convertible from a bike to a trike, so that's less weight that needs to be there as frame sections. Hard mounting the rear wheel makes it easier to build a frame around the driveline without trying to build into the mono-tube frame that's already there, and leave the mono-tube frame and related parts intact for use on my TwinStar, should the need arise.

Man, I'm hoping this project gets off the ground once the TwinStar is running (Which should be fairly soon, actually. It only really needs a battery at this point, and to finish the handle bars and seat pan.)

Yoosta hava Honda Big Red trike on the farm. Man I loved that 200 or was it 250cc engine!!! :eek: I always thought it would have made an excellent basis for a street machine; lots of power and it seemed very easy on gas.

Big Reds had 200 and 250 models, as well as 125's early on, I believe. The rear end of my TRX 200 quad is from a big red... larger axle, shaft drive, meatier in general. I gotta get that beast running and start pulling logs with it, too. Once again, if I had a list of all the projects I've got, the Statue of Liberty would have a hard time keeping it dry.

:turtle:

I'm all about creating new projects and never finishing them. :rolleyes:

I don't even talk about mine any more cuz I feel guilty about the backlog. :turtle:

Christ: Another reason to go with the 250 motor over a 125: you know you want 6 gears. ;)

How's that 'bent coming along? LOL.

The Atomic Ass - I might want manually controlled CVT in the end... depends on if I can build it or not. (Another project, of course.)

I'm assuming you were responding to me...

Take my advice and stick with manual gears. My Ninja just showed up by 4mpg my Burgman's PEAK, and it has very little to do with the smaller engine size. :)

yep, it was you I was referring to... sorry about that, I was paying more attention to my kid than the forum. Typing while playing with him...

Anyway, yes, I agree with the manual gears thing, but I have an "in my head" design for CVT that allows for manual selection of ratios without any automatic adjustments, and it's as efficient as a manual transmission with only 2 gears' worth of losses.

As I get around to it, I'll file the important papers for intellectual property, but I'll probably end up with an open source design, allowing others license to use as they see fit, but not to profit from it.

I'm trying to get a Ninja 250, though, that has minor fire damage... the plastics are all good, but some wiring burnt, so it don't run. I'm sure I can rebuild it for under $500, and it'll be a quick project once I start it.

The wiring harness of the Ninja 250 is profoundly simple. You'll spend more time unwinding it from the chassis than you will diagnosing and fixing the problem. :thumbup:

Let me know if you need the wiring diagram, I'll e-mail it to ya'. (it's a crappy JPEG, but most of it is somewhat legible.

It's 2 hours away, and she wanted $200. I offered her $100 if it had a title. I'll let you know how it works out.

Go ahead and shoot me an email: darkness.suspended@gmail.com

I can imagine it's about as simple as the one on my TwinStar, if not more simple.

If you shoot me an email, I'll send you the pics that the lady sent me.

It has a Yoshimura slip on, if that hasn't been sold off it already... I can probably get $35 out of that, to recoup some money.

Email sent. Everything that goes into a major component except the power block and ignition controller uses individual slide-on connectors, so you don't have to do any surgery on a component or fork out cash for a special connector when making repairs.