Gas Mileage

Techntrek,

As the above thread mentioned it might be better to have an airfoil than a spoiler on the back of the Pod.  I and a couple of other members used the 'airflow' software available on line to run flow simulations. The one noticeable feature of the flow regardless of the shape of the tow vehicle or if there was an A/C on the roof, was the large vacuum 'bubble' behind the pod.  Some tow vehicles along with or without a  air deflector on the tow vehicle would cause a momentary 'popping' of the vacuum bubble. On other configurations, there was a continuous lower pressure behind the Pod.
As far as I can tell no-one ran an airfoil simulation to see its effects.

On some vehicles there was smooth flow from the top of the TV up and over the Pod.
So I am now wondering if the low mpg is being caused, not by the frontal area pushing against
on coming air flow, but rather the drop in pressure behind the Pod pulling backward it.


I will try to run some simulations and post them here if no one else does.

    If someone was good at making a small scale model of the R-Pod. And if a wind tunnel could be made to place model of the R-Pod in it. The force pulled on the tongue could be measured using a string tied to the tongue then some sort of device to measure pull. Then different techniques could be tried to change wind flow and force of drag. Perhaps a scale model of ones TV could me tried to see how the combination of the two would cause drag. This is what I thought might work if it could be done. A fun project for someone with the talent and a lot of time on there hands. Does this sound like it might work or could be done?        David

I re-ran the airflow simulations with a couple of additions. 
A few caveats before you try to look at my animations.
The tow vehicle is a 2010 Chevy pickup with a topper on the bed.  I didn't try to run any open
bed sims this time.  I looked at a couple of photos from owners of the R-Pod 170 series with spoilers. The spoiler attachment point and extension out from the rear of the Pod is very approximate. Also the airfoil position is just a guess.  It takes a while to download an image to England and then have the animation sent back, so I just chose a simple flat foil, positioned approximately parallel to the rear of the Pod.  The 'angle of attack', size of the foil and position would probably make a big difference in its affect of the airflow.  I will attempt to run a few more
foil animations later this month.
Finally, as was mentioned on the Fall, 2009 animations, the real world air flows are probably somewhat different from the ones posted here.  I didn't use anything but the default parameters
available from the website. 
These animations were generated just to get a general idea on how the airflow moves over the Pod and how obstructions such as the A/C, spoilers, and foils 'might' change the flow.
The one thing that seems to be consistent from the present simulations and the many I did last Fall...is that the roof-mounted Air Conditioner has the biggest effect on air flow.  It tends to create the largest and most intense vacuum behind the Pod of any of the runs.  Foils and spoilers on the rear without an A/C on top barely changed the airflow.  The A/C seems to overpower any other
feature on the roof of the Pod.

(This is the first time I have tried to post 'avi animations' from Youtube on this forum...so if they don't work...I will try to post again later)

1) COMBO.AVI: my truck and Pod with no roof obstructions (A/C, spoiler, or foil)
http://www.youtube.com/watch?v=a9m5H1UEImc

2) COMOACZ.AVI: Pod with A/C on top
http://www.youtube.com/watch?v=DgYO4t5MwBc

3) CSPLAC.AVI: A/C on roof with small spoiler on rear
http://www.youtube.com/watch?v=J3Z8nl-CL_Q

4) CFOIL2Z.AVI: small foil at rear
http://www.youtube.com/watch?v=NT5ruDfD0OQ

5) CSPOILERZ.AVI: small spoiler attached to rear
http://www.youtube.com/watch?v=4Yi0ZtMCMv0

If one of you has a spoiler attached to your new Pod,  if you let me know the location and
size of the spoiler, I would be willing to run a simulation with a better representation.

This thread is a major let down for me. I've been reading up on lightweight RVs for a couple of months and the Rpod seemed tho be a good solution. I don't have a tow vehicle and did savor the thought of getting a V8 powered  tow vehicle. I wanted something to that a Ford Explorer or Chevy Trailblazer could pull including. I figured even these vehicles could even put an Rpod around the Rockies.