2011 Prius to get full boat tail w/ faired trailer
 

(Admin note: this thread originally started in http://ecomodder.com/forum/showthrea...-t-7839-3.html )

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An old college chum drove down from Colorado Springs in his new Prius for a day visit and 23-mile off-road bike ride below Lake Ray Roberts.Then a bunch of Tex-Mex to destroy any health benefits of our ride!
He liked the trailer concept and is going to do one for his Prius.
Harbor Freight Tools sells the same trailer I have at the same price I paid in 1986!
My friend will use the next step up the food chain,with larger wheels and radial trailer tires.
He has a THULE receiver-hitch bike rack already which will make for sturdy,safe towing.
We have the same engineering degree and perhaps he'll have some different and creative 'solutions' to the gap-fillers.
It'll be fun! Maybe low 60s mpg in straight interstate highway motoring.

Hi Phil -

That sounds like fun. Any chance you can encourage him to document his project here?

With the Prius already being a bit of a poster child for contemporary aero efficiency, I can guarantee that tweaking one with an aero trailer would attract a lot of eyeballs & show people that even the "good" contemporary designs have potential for improvement.

Darin

document
 

Darin,I've had him check out EcoModder.com so he's acquainted.
The nature of his endeavor may have to remain shrouded in a bit of mystery as it may entail more than one trailer ( if you get my drift).
But I'll ask.It would be good, and we could all commiserate together!
Cd 0.25-to- Cd 0.125 has an alluring aroma.

I would want to run the same wheels on both car and trailer. Depending on the aerodynamics adding two more wheels might add more drag than the trailer solves, particularly if the vehicle has good aero to start with.

He might try using zote foam as a connection of his panels. This was implemented by an artist friend of mine. I have used it on recumbent bicycles and it may work well as a trailing edge of a motor vehicle. It could be attached to the car and overlapped to the trailer. I doubt if an overlap is of much importance when going from larger to smaller.

wheel drag
 

I'm pretty confident that we can overshadow the extra R-R of the tires/wheel-bearings with the Cd reduction.
When I pulled the original 2-wheel trailer to California empty,and back loaded with a 1/4-ton of batteries along with all my other gear,I only took a 2-mpg penalty with the CRX,dropping from 52,to 50 mpg running 1,000 lbs over curb weight.That was without any gap-fillers between car and trailer,no 'underside',and zero wheel fairings.
I don't know yet if I can 'add' mpg,but I think it would be easy to net out at zero loss.
The T-100 should be less sensitive to a weight addition than the CRX and the Prius trailer could be constructed at no more than 200-lbs total weight.
Appreciate the Zote foam info,I'm sure my friend will be looking at all the posts and can value from the data.Thanks!:thumbup:

Prius trailer approved for ecomodder consumption
 

Just checked my email.My friend Gary says sharing the Prius trailer build on EcoModder.com is okay and he'll want to lean on as many of us as necessary.
Gary is going to do a 'shorty',only long enough to complete the 'Template' boat-tail without any consideration for carrying capacity.
He does regular I-25 runs between Colorado Springs and Denver and is indicating around 54 mpg with the naked car.So that will be the figure to beat.
I've been working 7-day weeks since November and have some savings built up to finance my return to the Viking project for World of Speed in Sept..

That's great news, Phil!

Any objection to me splitting the Prius trailer discussion into a new thread?

Darin

split
 

Darin,let's do it!,separate the omelet into its constituent eggs.

Ha! Good analogy.

Eggs separated.

(This thread was originally started in: http://ecomodder.com/forum/showthrea...-t-7839-3.html )

wait. so is this the old thread or the new thread? if it's the old, please point me to the new!

thanks

This is the new thread.

Edited my post to hopefully prevent confusion...

old/new
 

I've been working on the 'Full-Boat-Tail Trailer with Gap-Fillers for T-100 Pickup.
Rather than embed the new Prius project within that thread we've determined to dedicate a thread expressly for this project.
If you like,you can check out the other thread to come up to speed on the premise for these projects.;)

Priliminary Prius quanta
 

My friend Gary spent some time with the car.He got a couple helpers to sit inside while he measured.
* with 300-lbs ballast the height of the car is 58.2-inches ( 1455mm )
* point of maximum roof camber occurs @ 4.5-inches ( 112.5mm) aft of the B-pillar door joint.
* using the 'Template',the imaginary tail would strike the ground at 207-inches ( 5175mm ) behind the zero-point of the 'Template.'
* at 75% 'Template'( this will be my recommendation ) the back of the trailer will fall at 91.71-inches ( 2292.75mm ) behind the rear bumper fascia of the Prius.
* the elevation at the trailer body upper terminus is 24.5-inches ( 612.5mm ).
* in rear elevation view the body will mimic the Prius body tumblehome and evolve from there.
* Prius plan-view body camber and boat-tailing varies with position on the car.Very little at sill level,quite a bit as one moves up in elevation.The trailer body will pick up at these points and evolve.
* due to the original outside wheel width of 52.5-inches ( 1312.5mm ) I will recommend that the trailer tongue be shortened 5.82-inches ( 145.5mm ) to just maintain a 45-degree jack-knife swing,and go to a hyper-'Template' curvature in plan-view to allow enclosure of the wheels/tires within the footprint of the body.If done,the width of the trailer body rear will be 45.35-inches ( 1133.75mm ).Otherwise,to 'contain' the wheels with a on-'Template' plan-curvature,would require sectioning the frame and axle,a decision Gary will have to make.
* General Note:So far,cedar-strip canoe construction technology will be the fabrication path for the body construction.
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This is all preliminary,nothing is set in cement,and ideas will be bouncing back and forth between Sanger and Colorado Springs.
And so far,only the upper body is on the table.No bellypan,no wheel fairings.

So, not only will it be functional, but possibly extra pretty too.

Any hints on how gap filling between the car & trailer will be tackled?

FYI, the diesel trike that's been to a few of the Green Grand Prix events at Watkins Glen is cedar strip construction:

http://i39.tinypic.com/25kmz68.jpg

http://i41.tinypic.com/2rc7ihl.jpg

From: http://ecomodder.com/forum/showthrea...-may-7961.html

pretty----------------
 

Darin,Gary's pretty meticulous about stuff so I anticipate the bodywork to be really nice.
With respect to the gap-fillers,I think somebody will have to shoot me 'cause I keep re-inventing them in my head!
I hope to have some images to share before too long.Everything is pretty embrionic.Toughness is an issue with respect to road hazards and I want things simple and very strong for their weight.
Much of the panel system will be 'on' the trailer itself.Torsional coupling issues can be addressed this way.Less binding!
There will be an 'integrator' between tow vehicle and panel apparatus.
I'm close!
I'll show Gary and everyone what I've come up with and then 'ingenuity' can kick in.
That trike is rolling art work.Really sweet!

For your friend wanting more aero with a prius pulling a trailer. Design a one wheeled trailer. or a no wheeled trailer on a hitch. Stability issues aside more wheels = more significant drag.

I used to race hpv trikes and always took a big hit on drag from the extra wheel when compared to bikes. I did win the class 3 years in a row. I was over 50 then and raced against a lot of younger riders.

Hi Phil,

I did a quick drawing of "The Template" over a web image of a 2011 Prius.

http://i54.tinypic.com/2zoj4uw.jpg

Some things to note:

The Prius back glass drops quicker than the plan taper.

In order to make up for it, I shrank the template a bit and lowered it to put it in a sort of compromise position that you see in the image.

I did this because it would seem to me that once the air starts moving along a given taper, it would be unwise to push it back up too much, I'd think a sort of go with it idea would keep the air moving as smoothly as possible.

The black line was used as a measuring device, it appears to me that a trailer would end at 82" or so if this line were followed.

Anyway, hope this helps.

Charlie

one-wheel/no wheel
 

Varn,I hear what you're saying,but these designs are more ambitious than what Gary is willing to get into.
We're already looking at 800 man-hours just to get through a 'simple' design.And that does not include any metal chopping or welding other than the gap-filler mechanism which is not a mature technology at this point in time.
Of course,everyone else is perfectly free to go crazy with complexity.That's where I am.:o

drawing
 

Thanks Charlie,I've been working off photos Gary sent along with a Toyota factory shot of the 2nd-gen car in true-length.
I'm working @ 28-inch image scale ( car / trailer ) and have made allowances for differences between two cars.
I will follow the 'Template' in elevation which will produce a 'notch' behind the backlight,projecting straight back atop the spoiler 'til it hits the 'line'.There's nothing I can do about the roofline,so the trailer will just have to get back to the line on its own.There will be a locked-vortex captured in this area.
In plan-view,at the very base of the trailer we have issues.For the axle/tire width,@ 52.5-inches ( outside-to-outside ) the tires fall outside the 'Template' boundary.
Chopping the pull-bar a bit helps by moving the axle forward a smidge,but it still won't fit.Sectioning the spanwise frame rails and axle would fix this.
Gary will have to make the call on this one.
Leaving the standard width will force the trailer body to go hyper-'Template',widening the body significantly to allow enclosure of the wheels.
I've been working on the drawings this A.M. and will photo-reduce and scan
/post as time permits.
Right now,as things sit,the trailer body ends @ 75 % 'Template' in elevation.
Ground clearance,with projected Toyota diffuser angle is 14.66-inches.
Trailer body height,at terminus ( with the higher resolution drawings) is 22.25-inches.This will provide some area for the license plate and lights.
The small wake area should possess the 'phantom' tail phenomena.

Chop-saw and welder for trailer sectioning
 

Talked with Gary last night.
I'd completed the work up in side elevation,that was okay.I told Gary about the hitch when considering the view in plan-taper.
He's elected to maintain the original pull-bar length and go ahead and section the trailer frame to get it narrow enough to fit under the 'Template' footprint,allowing full enclosure of the wheels/tires at normal length and axle position.
This will facilitate the smaller wake,as per 'Template' profile and best chance for lowest drag.
I made enlargements this morning here at Copy-Pro and will try and finish the layout by next weekend.If so,I can scan and post what we have so far if I'm in town.
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The trailer is a 40.5-inch/48-inch ( 1,012.5 X 1,200mm ) frame with 12-inch ( 300mm )wheels/tires.It was on sale at Harbor Freight Tools for $ 189.00 ( US ),same price I paid for mine in 1986.It weighs about 140-pounds ( 63.63 kg ).
With ABS thermo-formed body shell the complete trailer would way under 200-pounds ( 90.9 kg ).
Retail prototyping expense for the first rolling unit will be approx. $ 80,000 ( US ).Retail price for such a unit in mass production would be on the order of $409.00 ( US ).

Drawings closer
 

completed preliminary side elevation images of Prius/integrator/trailer this A.M.,made copies first thing here at Copy-Pro today,and will work tonight on plan-view and rear elevation images after I get shop squared away for Viking.
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Also working on a dynamic model of gap-filler mechanism made from cereal box and push-pins which allows 'testing' of concepts.
I think I've 'nailed' the side panel articulation but need to spend a bit more time to prove that I've not gone down an intellectual cul de sac.
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If Al can help me tomorrow,I'll post the side elevation stuff,also Gary's photos.

Late in the thread, but here's another idea. A one-wheel trailer that could hold any thermo-formed box (custom shaped to your optimum boattail profile). No need for articulation clearances and could completely 'seal' to towing vehicle. Easier to backup and no jack-knifing.
http://motorcycletrailer.com/sw/imag...rrier1-500.jpg
http://www.smarterbuys.com/video1/SWmob1w.mov

Neat! Gets the neurons bubbling.

I imagine it would still need to be able to articulate up & down though (e.g. steep driveway entrance from flat road). Still, easier to solve gap fillers when the thing only moves through one plane.

1-wheeler
 

Sears Roebuck & Co. offered a 1-wheeler long ago.It has a nice cast-metal bumper attachment setup.The box projects back about 4-feet ( 1,200 mm ).Neighbor Bob's father owned one when he was a kid.
*There's a nice one on GOOGLE IMAGES behind a VW Transporter.
*What I don't care for,with respect to this design is the rather small castored-wheel with suspension ( much like the tail-wheel on a tail-dragger aircraft ).
The small diameter means high revs per mile which gets into bearing temperature/lifetime issues.
*The second issue I have is that if you lower the floor of the trailer to respect diffuser angle projection from the tow vehicle bellypan the wheel mechanism intrudes inside the cargo area,spoiling the usable volume.
*The third thing,is that if I pull away from a stop,in a right turn lane to make a turn ( legal in Texas ),at over 8-feet in length ( 2,400mm ),if there is a car to my left waiting at the light,I will rip its right side out with the trailer simply because it does not articulate.:(

some images ( finally!)
 

Here is some of the work-up on Gary's trailer.
I'm not sure about the order they go up with,so I'll comment on them after they're up.
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*1st photo,looking 'downwind',trailer hiding behind car
*2nd photo,2nd-gen Prius with aerodynamic 'insurance policy' to get best 'onset' flow rearward onto gap-fillers/trailer
*3rd photo,Harbor Freight Tools 48"X 40.5" trailer with 12" wheels/tires
*4th photo,trailer body,pushed to 'Template' profile
*5th photo,Trailer and 'integrator' which fills void between car and trailer nose and contacts gap-filler mechanism for panel articulation
*6th photo,2nd-gen Prius image,by Toyota,with side elevation shown in 'true-length' used in lieu of an accurate 3rd-gen side image
NOTE:
* 'Template' position was altered to agree with 3rd-gen Prius 0% roof camber position,while ballasted with 300-pounds dead load ( 136.3 kg )

Yes, the single caster wheel meant that it was locked to the car and so it would drive like a long tailed car; backing up would be a breeze. This is precisely what I like about this idea. I would think that a design could be done with a larger wheel that went up into a cylinder in the underside of the floor. The bottom of the "papoose" would have to be flush with the floor of the car, anyway?

That's the same trailer I had years ago. Except mine had 8" wheels which spun welded a bearing at low miles, low load, and low speed. The upsized 12" wheels are a huge improvement.

The other problem I had was both fenders fatigue failed early. Maybe the enclosure will prevent that failure mode too.

Given the short wheel bases and relatively tall tail height of the Prius (and thus matching nose height of trailer) I'd suggest generous allowance for pitching angle (upwards of course) to prevent the trailer from tagging the car.

I'm particularly curious to see how this rig will look from above. ;)

Rock on!

This project is too interesting.

I'm curious, though, did your prius need a trailer to begin with for extra storage? Or is this exclusively to improve aerodynamics?

Have you considered making the "aero-trailer" have a "fifth wheel" electric motor as well?

all the best

You could put that trailer to use and add some extra batteries there. extra electric motor is a little bit more challenging to manufacture, but power feed to prius electric motors arent so difficult task.

In europe you are not allowed to tow anything on Prius is it allowed in the states?

That's a good idea!

floor
 

Neil,did you mean 'floor' as in where are feet are,or the bottom of the bellypan/diffuser ?:rolleyes:

allowance
 

KB,the 'integrator' is hollow,shingling over slightly at the gap-filler package interface,allowing the rig to dip inside it when necessary.
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I completed the preliminary top/bottom plan-view drawings,plus rear elevation view last night.
I just now made enlargements and will darken the pencil lines with ink and scan/post asap.
Maybe Saturday by the latest.:)

trailer
 

Efficiency has always been a big deal with Gary.When he saw my trailer,he immediately made the connection and thought it would be interesting to see what he could squeeze out of the new car.
This project is for pure streamlining,as OTR rigs might one day use behind their semi's,so it,in itself will carry no load.
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A 'pusher' trailer has already been addressed here at EcoModder.I am personally opposed to the concept,but only for safety reasons.
Event-horizon vs human reaction time might create a regrettable situation in a worse-case-scenario.
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The trailer is intended to be used as an electric-vehicle range-extender,carrying a second set of batteries, or gen-set ( to create a serial-hybrid ).
I saw three EV trailers at the Solar-500 at Phoenix Int'l Raceway in the 1990s.I surmised back then,that all three vehicles could have extended their range had they seriously considered streamlining.
Alan Cocconi made an effort to soften the body of his trailer,but it would have been completely submerged within the turbulent wake of his CRX.:(

extra batteries
 

Hauling extra batteries is one of the premises for the invention.
An extra 2,000-lbs ( 909 kg ) only costs 2.94 horsepower in additional road load from rolling resistance at 50 mph ( 80.5 km/h ).
At 55 mph ( 88.5 km/h ) Gary's trailer can add 11.3 mpg from drag reduction,with 3.77 mpg loss due to R-R ( radials ),4.1 mpg loss ( bias-ply ),for a net improvement,from 53 mpg,to 60.2-60.5 mpg at steady speed.
---------------------------------------------------------------------------- A Nissan Leaf,or plug-in EV,on a road trip,would extend the range of the initial battery pack,and carry the second pack with no penalty,only gain.:thumbup:

Prius Tadpole Performance Estimates
 

The following predictions are made for the project if built to drawings:
NOTE: since this trailer carries zero 'load',it is by default,over-engineered.Consequently,approx. 21.5-lbs ( 9.77 kg ) can be removed selectively from the original trailer without sacrificing structural integrity
* 'shaved' weight,trailer kit = 118.5 lbs ( 53.86 kg )
* thermo-formed ABS plastic top = 32 lbs ( 14.54 kg )
* thermo-formed ABS plastic belly = 19 lbs ( 8.63 kg )
* thermo-formed ABS plastic wheel/leaf-spring/axle fairings = 20 lbs ( 9.09 kg )
* with steel out-rigger body supports and gap-filler mechanism,all-up weight of complete trailer = 225 lbs ( 102.27 kg )
* with 15 % tongue-weight = 191.25 lbs ( 86.93 kg ) on axle
* rolling-resistance penalty @ 55 mph ( 88.5 km/h )= 4.1 mpg ( bias-ply tires )
* ditto ------------------------------------------ = 3.777 mpg ( radials )
* modified wake area = 1.632 square-feet ( 0.151 square meters )
* modified drag coefficient = Cd 0.143
* aerodynamic drag benefit @ 55 mph = 11.3 mpg
* net gain from trailer based on tire type = 7.2-7.5 mpg
* predicted new fuel economy @ 55 mph = 60.2-60.5 mpg at steady speed,from a baseline of 53 mpg ( current tank mileage ).
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Many hundreds of hours from now we'll know something!;)

Hi Phil,

I meant the underside / bellypan / diffuser.

Understood, Phil. I was also thinking about interaction scenarios. Consider pulling out of a gas station through a gutter dip onto a crowned road. While executing such a turn rigs can experience yaw, pitch and roll at the same time. Once your trailer tags your tug (ask how I know) you get extra cautious...

underside
 

Hi Neil,
to have the bottom of the papoose projecting along the line of the tow vehicles diffuser angle seems to be the desired geometry so that would get you the lowest drag.:thumbup:

yaw,pitch,roll
 

KB,I've deceived myself before on projects,so until I actually test the silly thing I won't actually 'know' how it will perform in the real world.
The drawings will explain themselves best but they are time away.
I did a photo shoot of the wind tunnel,got it put away,and Viking is finally back in the shop,so I feel like I'm making a little progress.
So the drawings are on the burner,as Gary will need them too.
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Here is a description of where my thoughts are :
*the side gap-filler panel frames pivot from frames which themselves pivot from an axis above the ball-hitch.A link connects the side panel frame to the wedge face of the trailer to create a 3-bar linkage.
-------------------------------------------------------------------------- The top panels pivot vertically from a frame & post which receives into a tube above the swing points for the side panel frame support frame,which can displace from side to side like a lolly shaft on a windmill.
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All the panels are supported on the trailer itself and cannot bind against the trailer under any orientation,as they move with it.
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The integrator is designed to contact rollers mounted low and outboard on the swing-frames which support the panel frames.
*When the tug yaws,pitches,or rolls and the integrator contacts the swing frame,it will displace rearward.The link will force the trailing edge of the panel frame to displace outward,taking the panel with it for the clearance articulation,with a maximum yaw of 45-degrees.
As the yaw,pitch,or roll 'event' ends,and the tug straightens back out,the link forces the the panel frame to 'close',which in turn forces its supporting swing-frame to 'stowed' position under spring tension.
Nothing happens on the unaffected side.It will just remain in the 'stowed' position.
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If the rig goes over a high point,everything moves away from the integrator.
If the rig goes through a dip,the swing frames and upper frame can dip inside the upper void of the integrator.
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So far,the split lower panels are unresolved.I'm close but no cigar quite yet.Safety chains and landing gear issues must be thought out.
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The images will help a lot so I'll chip away at those.In the meantime,maybe the above explanation will help.:o

Thanks for answering back! I'm really looking forward to keeping up with your project.

sincerely