Aprilia SR 50 R

[Frank]

For sure a Kamm tail would help, covering 50% of the front wheel with a bigger fender is good. I'd also consider trying to cover the rear wheel (think hubcaps). Bringing the front fairing back is also probably a good thing but make sure you can get your feet out quickly!

[JacobLeSann]

Going good at this stage! You can look at the rest of the uploaded photos on this status and see the different methods I tried. First plan was to allow full wheel clearance and use the same heat-molding process I did to make the seat. That was way too bulky. I ended up trying out a cardboard mock-up with two wheel-bumps design to look like vents. That is still rather ugly but certainly looks better and almost matches the scoot’s curves. I’ve read that a stepped-design like mine can help break up crosswinds better, so I hope that’s true.

The flat section makes it look like a formula 1 wing. I will of course cut that down, but I’m leaving it intact right now as I stitch up the floor pan for the fairing.

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The kamm-tail. That’s a bugger. I need space for my backpack so I plan to take the old storage pod the bike came with (can be seen in the very first post in this thread), and turn it into a kamm-profile. I want to leave the rear swingarm open, despite the large effect on drag it creates. There’s alot of moving stuff back there as well as turn signals and a brake light. It would be a real challenge to get that working with given suspension clearances, exhaust clearances, proper air intake flow, etc. The whole drivetrain of the bike is on that rear arm, and it deflects by a surprisingly large amount, so having it open is far less of a design headache.

[JacobLeSann]

https://youtu.be/F3hM3CjVABI

I finished up the rough fairing! My phone is having issues with uploading so here’s a sneak peak from my YouTube channel. After around 50km of burnouts, highway pulls, and top speed runs, the scoot still gets an estimated 100 MPG or 2.35 litres per 100km. I was not able to break 83 km/h so I looked into it and believe the bike has a restricted ECU. With the aero streamlining it smoothly purrs up to top speed, but then it just cuts power on me. Even on downhills or drafting trucks. It holds top speed easily with what seems like just a little load on the engine, so I’m sure it can go higher.

The fairing is actually practical so far. I would freeze a lot previously and come home shivering. Now the only things to get cold are my hands. I rode a good 40km of highway at 80 km/h in -3 degrees Celsius; not bad at all. It does seem stable as well: I was passed by several semi trucks and noticed no impact from the turbulent wake behind them.


I am wanting to design better streamlining at the rear. The front is well done and splits air around me without increasing wake too much. I don’t think there’s much for air to reattach to down low in the rear. A tail is smart but like I said lots of parts on a moving swing-arm with good travel to it; complex.

[cRiPpLe_rOoStEr]

Originally Posted by JacobLeSann

I was not able to break 83 km/h so I looked into it and believe the bike has a restricted ECU.

AFAIK the restricted ECU was only used in countries where it was supposed to be legal to ride one without a motorcycle license, or without a license at all.

[JacobLeSann]

Yep, that would be my country. I don’t have a motorcycle license (moto insurance is cost-prohibitive in my area), and I’m happy I can ride this without.

I plan to make a proper YouTube summary of all the work I’ve done to this bike.

Have added some bodywork to the rear and hit a rough estimate of 114 MPG. I’m not too impressed with this figure and I hope it’s a result of the cold weather outside. Been riding it between -10 Celsius to -2 Celsius. Have ridden 110 km so far; 1/3 of a tank left.




Here’s a pic of the bike as of now. I added two rear panels after my dissatisfaction with 100 MPG. Kept the length short to avoid making a parachute for crosswinds. It brought mileage up some. I am going back and forth about the angle of the spoiler atop the storage pod. I’m not sure if lowering it to horizontal or angling it downward will make a difference given the amount of turbulence behind my helmet.

Of course these figures are based on the fuel gauge readout and odometer distance. I have nothing else to go of off until this tank is burned. I don’t take them to be too accurate.

[Joggernot]

On a lark, I put your photo on the "template" just to see the result. The first shows from the top of the windshield to the spoiler and the second shows from the top of your head to the spoiler. Might give you an idea for spoiler placement.

[cRiPpLe_rOoStEr]

Originally Posted by JacobLeSann

Yep, that would be my country. I don’t have a motorcycle license (moto insurance is cost-prohibitive in my area), and I’m happy I can ride this without.

AFAIK the restricted ECU was limited to 50km/h which was the maximum speed allowed for unlicensed riders in most jurisdictions where restricted scooters and motorcycles up to 50cc were registered as a moped.

What top speed had you reached prior to aeromodding?

[JacobLeSann]

Joggernot, those are some helpful images, thank you! It looks like the first image with the template aligned to my windshield is close to what I have done with the bike currently. I don’t want to add more above the storage clamshell as I already have quite a lot of surface area for crosswinds to catch. I think it looks nicer as it is, too.

In regards to top speed, that one is uncertain. I remember I drafted a semi truck one time and got close to 90 km/h. But when it comes to evidence, I have nothing that shows me going above 80 km/h. I was able to get above 100 MPG on the non-modified bike, but that number decreased as I moved from 60 km/h to 70 km/h as my cruising speed. That is now different.



The bike is pretty much done, in terms of rough work. I got a Gianelli Reverse exhaust and that seems to have moved the powerband up a bit. The bike is slower from a stop but it pulls much better at high speed. In gusty conditions, I can reliably hit 85-90 km/h. The bike is noticeably more affected by crosswinds, but not enough to be a problem. I’ve improved rear bodywork quite a bit and I think that helps. It looks like the exhaust has unlocked more power which allows me to take further advantage of my aero mods.

I will be painting everything up soon, so maybe I’ll test the naked bike out and compare. Been busy with Easter and other things so didn’t have enough time to test possible gas mileage estimates.


Here’s a fun video I made on the fly:

https://youtu.be/bGdhn9Ymy5E

[freebeard]

The spoiler is pointless, it's occluded by your head and shoulders. IMHO, of course.

Put a tail fin on your helmet and see if you can steer in crosswinds with your head.

[cRiPpLe_rOoStEr]

Originally Posted by JacobLeSann

The bike is pretty much done, in terms of rough work. I got a Gianelli Reverse exhaust and that seems to have moved the powerband up a bit. The bike is slower from a stop but it pulls much better at high speed.

A different exhaust really changes the behavior of a 2-stroke. BTW doesn't it have any sort of "power valve" such as Yamaha's YPVS?