UCF Human Powered Vehicle

UCF Human Powered Vehicle

Paul
aka Trebuchet03
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By trebuchet03

3 ratings

- Video 1 -

This project is not at all 100% my own. This was a senior design project at my school - I offered my assistance as an advisor and helped a little bit with construction and such...

This is a short wheel base recumbent with a full fairing. We competed in the ASME Human Powered Vehicle Challenge - East Coast. As such we were required to have at least (or equivalent) roll over protection of 1.5" chro moly steel with a .049" wall thickness. The goal for this year was simple. Build a bike that works and can put power to the wheels reliably. Sounds like a silly goal, but last year was a train wreck ...

Top instant speed: 34mph
Trap Time: 7.10 seconds
Trap Speed (100m avg.): 31.5mph
cD ~.15 -- about 5 lbs of wind resistance @30mph
Steering: double U-joint
Drive: Dura Ace 52 (I think) front chain ring/the new Nexus 8 internal gearhub rear with 16 tooth rear sprocket
Weight (total): Never Measured together ~50lbs
Fairing Weight: ~23lbs
Flow Separation occurs at the beginning of the "C" on the UCF decal.
Still waiting on competition results

The frame backbone is a single tube of chro moly meeting the rollover protection standards - frame fabrication was done at Mazworxs. Fairing was constructed from a male plug. Two layers of 8.5oz glass mat was used on the inside, 3mm Kmat core and one layer of glass on the outside. The whole thing was put into a vacuum bag and we pulled 10psi for several hours (at 1 atm the plug began to collapse). The whole fairing was made as a single piece and portions were cut away.

Fairing construction was done at Lockheed Martin Missle and Fire Control - the team did all of the work while our contact at LM offered his 30 years of experience... When finished, they asked why we built a frame - it is VERY structural which did come in handy later...

The frame is attached using 5 Dzus fasteners (two in the rear, two on the side and one in the front). The two side mounting points also add side impact protection which was well used.

If you want to know more about construction and such, just ask ;)

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Its like riding a bike, only harder (as said elsewhere). But once you got it... you got it and its a dream. Visibility is excellent (no worse than a motor bike with helmet).

The officials persisted on starting the endurance event even with all of the rain and puddles on the track (A Nascar Tri Oval). Our female rider did not get as much time to learn to ride as most of us... She had a rather serious crash just before the 40 mile endurance - her skid mark was about 30 feet long. The fairing protected her, however she put her arm down (instinctive) - she went to the hospital (A-OK) but not before starting the race and completing her minimum 7 laps. The fairing sustained some damage, but nothing critical (the rider IS more important).

Unfortunately, that last picture does not have the whole team - some members were at the hospital.

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PS, if you want to see some amazingly well crafted bikes/works of art. Check out Vanilla Bikes - a local bike shop happened to have one, in which the jaws dropped to the floor.

By damonv

2006-05-10 20:17:22

Awesome project! I was involved in designing a speedbike, so I'll just tell you what strikes me about your design initially, in case it is of any value to you. It looks really friggin' good, but I still have some things to say. You've probably head a lot of them brefore too, and perhaps had design reasons (I'd love to hear them!) to do otherwise.

1: laminar flow is key. Your overall shell shape looks good so far as I can tell from pictures, but having breaks near the tip disturbs laminar flow. This is the problem with having your shell split anywhere near the frond.

2: cross section is the most important thing you can worry about. If you can shrink your shell by 1 inch width, then well... you know... you go a lot faster! You have the rollbar requirement to deal with. Our solution to this was to make a composite rollbar. This kind of sucks weightwise, but the aero gains are well worth it

3: vacuum forming! smaller windows looks cool, and reduces weight, hence their use on SS1. The problem is that more windows means more interfaces to trip turbulent flow and muss up your tiny friggin' aero drag.

4: foot extension ports. These are pretty neat looking, and probably good for something practical. The problem is that they also mess with aero. The thing we thought of doing was to put a rollerskate wheel on an extendable stick. This has a smaller interface to muss with drag. It's hard to find a place to fit it, though.

5: FWD or over-the-shoulder chain. This also helps reduce your aero cross section. Remember that your drag is going to scale with cross section, pretty much, so anything to cut it down is good.

That's all I got now. Don't think that I'm bashing your project. It's a hell of a lot more than we ever accomplished. This is just stuff I was told by all sorts of aero genius profs at MIT that I thought I'd pass on.

damonv

By trebuchet03

2006-05-10 22:01:23

Hey no worries ;) We're always open to ideas and such - after all, the competition wants to see innovation in the field :P

1. I agree - actually, almost all of us agree. Not quite sure what happened there. You might be able to see that the front does not sit just right. My guess is that some internal stresses formed there...

2. This fairing has given us an excellent view on where we can trim off a bit. I will be suggesting some sort of air ventilation ducts (probably NACA) to make fully faired more comfortable...

3. We were hoping that the monoqoque would not sink down as much as it did. Another reason for the window design was strength. Compared to a single large window, these circular windows keep rigidity (I'm sure you guys know all of that though :P)...

4. I made this suggestion... but the team decided not to do so. I think I am going to push harder for landing gear for next year's design. I came up with a design that was basically training wheels (on both sides) that could be lowered and 'locked' - they probably won't go for it during the sprint event because of weight though...

5. We did FWD last year (only team to do so - this year there were quite a few FWDs :P). Part selection was bad - instead of bearing carriers, self aligning pillow blocks were used.... Apply torque and they self aligned - chain popped off. That team only had 3 months to design/build - so I tip my hat to them. But this year, we wanted a machine that did not require machining in the hotel room with a power drill and JBweld.

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I found out today.... We scored 6th overall... IMO, that is excellent as last year we scored 13th :P I'd love to see you guys come out next year (I'll be here for at least two more years) - I'll get to meet some of the crazy inventors here :D

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I'm also back at home... and I found out that I now have access to a rather beefy vac pump :D I might just be making a partial fairing for my wooden 'bent that is slowly forming :D

By damonv

2006-05-10 23:26:27

that sounds awesome. It looks like you guys know pretty well what you are doing.

Unfortunately, we probably won't be building anything for next year unless we start after the summer. We are working currently on getting a bunch of solar car teams over to MIT to redefine that competition and build some more practical vehicles. Not just solar cars either, which I guess is implied with saying "more practical". Pedal-solar is one thing we're looking at, with both an array and some batteries. I kinda want to build a motor scooter that can break into two 50 lb bags and fit into some airplane luggage.

For the landing gear, are you sure you want _any_ for the sprint competition? I mean, if you have a catcher at the end, it might be good enough, and it removes a bit of weight and drag.

Something that's good to do for the aero agian, and this is one suggested by Prof. Drela (holder of human powered water vehicle record) is to have the nose all be one piece, instead of split into two. This leads to, firsly, more laminar flow! excellent! Second, it leads to a stonger structure in the front, which means less worries about windows bending (though the wind buffeting eventually becomes the concern). The vehicle split can then either and behind or below and behind the nose. Also, a sharper nose is probably more efficient. The best inspiration for shape, other than other HPV's such as those by matt weaver et al, would be sailplane fuselages. Those are incredibly low drag, and are at about the same reynolds number.

Good luck with the wooden bent too, that sounds like it will look incredibly awesome. Perhaps I will finish with my wooden rowing shell oars soon =)

By trebuchet03

2006-05-11 13:44:42

Yeah, you're right... just catching the rider at the end of the sprint is a better idea -- it worked this year :P

One team had a 24 volt, 10 lb Nimh gell battery... I don't know the amp hr. rating, but it sounds like the perfect type for a lightweight pedal/solar vehicle -- but I'm sure the solar guys have done their HW :P

Next year's fairing is def. going to have the roof line cut differently to keep the nose a single piece. As for the blunt shape, we have a design constraint (we set for ourselves) to keep length under 60 inches - we barely made that I think - but it can always be trimmed and streamlined from here.

I have to get them from another member... but if you want to see the wind tunnel testing - we have pictures of a rapid prototype model with wool tufts... The results from the tunnel confirmed that the model in Solidworks Cosmos and Fluent were close to accurate.... Just curious (if you know), what was the resistance of the water vehicle? - just curious of how much effort we should put into lowering our Cd OR if that effort should go into lighter materials...

By damonv

2006-05-11 23:49:51

The wind tunnel testing sounds really neat. I'm actually very suprised with the accuracy of cosmos. I haven't used fluent, but I know that with all the arbitrariness of cosmos, I figured it was making shit up and then telling it to us, even though the simulation was outside of it's constraints. That's just the feeling I got. But hey, if it works well, that's awesome! I should use it more!

The water vehicle was a hydrofoil. Each hull was a women's kayak made by a local high-end racing shell manufacturer, Van Dusen, I believe. They weighed 7 lbs each! wah! They started with some very large hydrofoils, and then slowly pushed them down to the limit of cavitation (hence the decavitator, perhaps). That is, they kept on decreasing foil size until the the low pressure on top of the foil was close to the vapor pressure of the water.

My humble opinion is that you should focus on both. Design a shape that is aerodynamic, and then to a monocoque bottom shell, perhaps including the nose. The shape of the shell won't matter too much for structure here.

I guess, this being my pet project before we got started on this solar car stuff, I would look into making a composite rollbar. Cosmos simulation would be a good way to figure out the specs you need. If you made one and tested it, that would look really good at the competition, too. It should be made of kevlar and/or glass mostly, although it wouldn't hurt to have a little bit of carbon in there too, for rigidty. The carbon, of course, will just snap when it gets hit too hard, and not soak up much energy. So long as the rollbar is strong enough, it will only break at the point that you, say, hit a curb in a slide after a crash, and then the remaining sections will act as high-loss springs soaking up the rest of that energy.
And with this design, you can get your shell size down until it's just around the rider's shoulders, and still be safe in crashes.

By notbehavin	2006-06-09 02:10:12
If you don't mind me asking can you please tell me all of the materials you used to make your h.p.v?

By trebuchet03

2006-06-09 20:38:43

hehe, I haven't checked the site in awhile -- good timing though :P

The main support member is 1.5" chromoly .049" wall thickness. We were required to use this for the roll over protection - so we used one long piece with mandrel bends. The boom (portion that supports the crank) is made from the same piece of pipe.

I don't remember the specs offhand for the other chromo parts - but it was made from chromo... I think that's Steel 4130. Most vehicles are made from this material.

I think the front for was made from alum. But this was a bought item. The rear triangle was fabricated in house allong with the dropout brackets (rear wheel attaches here) which were cut from plate steel.

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The fairing is made from 3mm Kmat core and fiberglass shells. A few other teams used similar materials for their fairing.

If anyone reads Autospeed (an online Australian auto magazine) - they are doing some articles on HPV design and a contributor is building one for himself... If you know someone with a subscription, it covers a lot of basics on materials selection, design, etc.