Critique this velomobile body

[The Toecutter]

Originally Posted by aerohead

Your trike is gonna be more like a 2-dimensional airfoil than a 3-D bluff body.

Noted. I've seen bluff bodies with a Cd in the low 0.3 range and figured that I could get similar results, and then tweak it over time after the turbulent areas were found.

A symmetrical airfoil section with an aspect chord-to-thickness ratio of 3.92:1 has been found to be the center of the drag 'bucket',with both minimum pressure and skin friction drag.
You could maybe think in terms of both the body and canopy designed around this geometry instead of the template.

Would this be very close to the NACA 0025 and 0026 airfoils?

I agree with the others on the front lower angle.I wouldn't do that.
All the intersections will have hook-vortices unless there's a fillet to smooth the intersections.

Noted. I worry about speedbumps and potholes. I will have a ground clearance of roughly 5.5 inches when all is said and done.

Goro Tamai's book on solar racers would have some data you could use in addition to member comments,of which have,'been there,done that!'.

Thanks. I have not even heard of this book and feel compelled to read it. I do plan to put solar panels on this thing some day, and a body with a lot of flat-surfaced top area with minimal sources of shade would be good for this. Fitting a 0.5 m^2 set of panels at some point in the future is a nice thought.

Rumpler's Tropfenwagen was Cd 0.28 for the closed limousine,and Cd 0.54 for the roofless,open touring car.

I didn't know what it was for the open top car. I knew that the enclosed model was a 0.28, roughly what the average 2017 model year car claims to have(and usually, independent wind tunnels put their figures a bit higher, Tesla being about the only exception that has consistency between manufacturer claims and independent verification).

Without a half-bubble windscreen Cd 0.25 may be problematic.

Noted. I plan to make a removable ducted cover section with a roof and windscreen to shield the rider's head, but I'd like the aerodynamics to be good enough to where it isn't really needed.

One of the IHPV members ran a all-Coroplast-bodied trike in 2014 at Battle Mountain,and I want to say that he came through the 5-mile trap at 47-mph.
I'm pretty sure that the wheels were enclosed and he had a bubble screen.

I've seen pictures of it:



Unfortunately, my trike is too wide to make that sort of body work for my needs. It is well done.

[Ecky]

[kach22i]

Lots more curved edges, more complex - a different path.

2009?
Quattro
Kingcycle - Quattro






Some cool history behind it.
http://www.kingcycle.co.uk/page6.htm

At least three other projects documented.
http://www.kingcycle.co.uk/page7.htm

[The Toecutter]

Have you taken any measurements to determine the gains from that tailbox, Ecky? I'm curious to see if it increased your cruising speed and top speed.

I've come across the Quattro during many online searches. It is an interesting machine and I'm sure Mochet would have been floored had he been alive to see it. I suspect that it's overall aerodynamic drag is similar to that of a Quest velomobile.

However, I'm more partial to the commercially-produced QuattroVelo:

https://www.velomobilcenter.dk/galleri/velomobiler

That is the sort of shape that modern entry level sportscars should have.

[Ecky]

I need to wait for my motor to get here for that. The controller and display I use have a watt meter and speedometer.

[Grant-53]

https://www.flickr.com/photos/okpete...7651905111646/
This a popular design currently being used. See The Recumbent Bicycle and Human Powered Vehicle Information Center
I use the cut and tuck method too. Start with cereal box cardboard 1/4 scale models. Sailplane designs are very similar. Air intake along the canopy cowl and exit behind the head. Cooling at the neck is very effective.

"Race Car Aerodynamics: Designing for Speed" by Joseph Katz is useful also.

[Bicycle Bob]

Try to think of this project as an easy-to-modify experiment to get familiar with the issues and how they affect your enjoyment on the road. I have drawings for faired and unfaired pedal trikes on my board, and the chassis have distinctly different proportions, suspension, gearing and braking, for very good reasons. Adding power has similar effects.

[The Toecutter]

Originally Posted by Ecky

I need to wait for my motor to get here for that. The controller and display I use have a watt meter and speedometer.

I just reached 29 mph today on flat ground. No motor. no body. The only aeromod is wheel disks. It was my first time testing the new Schwalbe Tryker 20x1.5" front tires I put on it to replace my Maxxis Hookworms. This was during a 30 mile ride to the next town over and back. I'm really looking forward to a body shell on it...

Originally Posted by Grant-53

https://www.flickr.com/photos/okpete...7651905111646/
This a popular design currently being used. See The Recumbent Bicycle and Human Powered Vehicle Information Center
I use the cut and tuck method too. Start with cereal box cardboard 1/4 scale models. Sailplane designs are very similar. Air intake along the canopy cowl and exit behind the head. Cooling at the neck is very effective.

"Race Car Aerodynamics: Designing for Speed" by Joseph Katz is useful also.

I like this design a lot. I first came across it on the internet about 2 months ago. The doorway clearance issues prevent me from using it for my build without radically altering it, and given that my trike is a wide 39", my version would likely have a frontal area around 0.75 m^2 were I to replicate it.

I need to find a copy of that book as well.

Originally Posted by Bicycle Bob

Try to think of this project as an easy-to-modify experiment to get familiar with the issues and how they affect your enjoyment on the road. I have drawings for faired and unfaired pedal trikes on my board, and the chassis have distinctly different proportions, suspension, gearing and braking, for very good reasons. Adding power has similar effects.

It is a rolling science project for sure, but it is also going to meet the majority of my transportation needs. In the long term(possibly this winter) I plan to make a 200 mile trip to Austin, TX in it. The motor I am putting in it is going to produce 4 kW or more, and the top speed will be in excess of 45 mph, maybe up to 55 mph depending on gearing.

[Bicycle Bob]

Originally Posted by The Toecutter

It is a rolling science project for sure, but it is also going to meet the majority of my transportation needs. In the long term(possibly this winter) I plan to make a 200 mile trip to Austin, TX in it. The motor I am putting in it is going to produce 4 kW or more, and the top speed will be in excess of 45 mph, maybe up to 55 mph depending on gearing.

J. Baldwin, long-time tech editor of Whole Earth Review, says that it usually takes three tries to be satisfied with a new design. The second prototype fixes up the obvious problems with the first, and the third smooths out most of the remaining irritations.

[The Toecutter]

Originally Posted by Bicycle Bob

J. Baldwin, long-time tech editor of Whole Earth Review, says that it usually takes three tries to be satisfied with a new design. The second prototype fixes up the obvious problems with the first, and the third smooths out most of the remaining irritations.

I have sort of figured this project wouldn't be completed until at least the 3rd body. I do want the first one to be at least usable and practical with a decent drag reduction. That's why I've been taking my time with it. I'm only designing to cruise at 30 mph or so, but the high top speed will be a consequence of gearing to do 30 mph with a cadence of 80-90, when I'm still capable of holding a cadence of 140 for shorter durations. I know of a KMX build with a 6.5 kW middrive though and it's rider can safely cruise at almost 40 mph and has been taken to 60+ mph a few times. The steering knuckles and stock wheels are the weak points of the KMX frame kit when it comes to tolerating road imperfections and hazards, but the knuckles can reliably handle cruising at 30 mph or so *IF* you have a front suspension setup, according to this builder.

I'm also partially inspired by the efficiency that Cedric Lynch has achieved in his electric recumbent motorcycle, roughly 30-40 wh/mi to do 50+ mph:

https://www.youtube.com/watch?v=b4BAnH52-g4

https://www.youtube.com/watch?v=KnqoH0YaCsE

Adding a small amount of human power to that will yield more than marginal improvements in efficiency, and pedal power is awesome for extending your possible range to the point that even if you somehow cannot get electricity anywhere, you'll be able to still go anywhere that you can pedal it. It must be light enough to be pedaled, and geared so that at least a fit rider could climb steep grades at 4 mph. I think 100 lbs or less is a good target. There's a lot of efficient custom-build vehicles out there that are too heavy, but are worth drawing ideas from.

Adding some ass-hauling capacity with an overpowered drive system would make the vehicle fun and more appealing to hoons, and less prone to getting laughed at by the general public, as well as the practical application of being able to get away from a dangerous situation as well or better than most cars.