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Old 07-20-2021, 07:54 PM   #11 (permalink)
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I spotted a '08-'09 Dodge Ram 2500 with a coachbuilt motorhome body this Sunday, and its proportions reminded me of an ambulance, even though it had a sleeper over the cab that smoothed its frontal area a little. Maybe getting a light truck instead of medium-duty can be beneficial, as the lower cabin may keep room to add either more storage or sleeping area without increasing the overall height.

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Old 07-20-2021, 08:38 PM   #12 (permalink)
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An inflated half-round on the vertical edges would help as much as the deflector. Assuming they run all the way to the top.
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Old 07-21-2021, 09:19 AM   #13 (permalink)
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An inflated half-round on the vertical edges would help as much as the deflector. Assuming they run all the way to the top.
Are you talking about the front or the back of the box? The industry has gotten more creative in recent years to improve aero without the inconvenience of requiring the driver to fold in rear flaps. (Innovation driven by recent federal mandates for trailer manufacturers to reduce drag - both aero and rolling)

So in addition to flaps there are little fairings like Michelin uses:



I also won't have a smooth top to the ambulance. I'm planning about 1400 watts of solar and at least one powered vent.

and also little turning vanes like Rockettail



The problem (for me) is that they are generally tested as a complete kit with underskirts, wheel covers, and other aero aids.

I also won't have a smooth top to the ambulance. I'm planning about 1400 watts of solar and at least one powered vent.
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Old 07-21-2021, 10:20 AM   #14 (permalink)
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Thanks for the reasoning on why not a truck. Low access height does mean you will have wheel arches to contend with.

You need to check on jurisdictions, our ambulances sometimes have the side door, but always have the pass through. Everyone specs out their needs differently.

6mpg isn't bad for something driven with two pedal conditions: full on and full off. I suspect they would get 12-13 driven sanely which is what I got dragging my big boxy unaerodynamic toy hauler.

Solar on top shouldnt add to much friction drag as compaired to a/c and emergency access mandates.
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Old 07-21-2021, 12:14 PM   #15 (permalink)
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better

From what Hucho shared in his chapter on commercial vehicles, and NASA's reporting, the Daimler-Benz Freightliner would have the advantage.
Daimler's design blows a bigger hole for the box to trail behind, and that added width and height better takes more of the leading edge hit, than the horrible face of the box.
Ideally, the cab would be just as big as the box, as with Tesla's Semi/ NASA's semi, most current Class-8 rigs operating at a profit.
It's the difference between Cd 0.89 and Cd 0.41.
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Old 07-21-2021, 12:17 PM   #16 (permalink)
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Old 07-21-2021, 12:25 PM   #17 (permalink)
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air deflector

For sure!
If you could seal as much of the gap between cab and box, that would also show. ( delta-Cd 0.016 on my pickup )
Also, extend the box sides down even with the bottom elevation of the running boards / step.
Wheel arches?
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Old 07-21-2021, 12:42 PM   #18 (permalink)
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I'll point out that the purpose of an ambulance isn't to get great fuel economy.
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Old 07-21-2021, 12:50 PM   #19 (permalink)
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Thanks for the reasoning on why not a truck. Low access height does mean you will have wheel arches to contend with.
Yes, I will have wheel arches but Iím willing to put up with them for a low step-in height. One design Iíve seen that seems to work well is to leave the two jump seats over the wheel wells in the final conversion with a flip up table between them for dining. That not only gives seating for eating but also gives two certified seats with seatbelts to allow passengers to legally ride in the back.

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Some ambulance layouts work better than others for camper conversions. The ambulance above isnít ideal due to the tall vertical outside cabinet with the yellow X. That would need to come out to put a bed across the back.

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You need to check on jurisdictions, our ambulances sometimes have the side door, but always have the pass through. Everyone specs out their needs differently.
Yes, every ambulance is a bit different. The only ambulanced Iíve seen for sale without a side door are Red Cross vehicles. There are a bunch of these trucks for sale right now (Mid-2000 Fords with the 6.0L Powerstroke) Although advertised as ambulances they arenít really. They are ambulance bodies that are basically empty inside and used for delivering disaster supplies.



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6 mpg isn't bad for something driven with two pedal conditions: full on and full off. I suspect they would get 12-13 driven sanely which is what I got dragging my big boxy unaerodynamic toy hauler.
This friend does not drive with the gas pedal as an on / off switch. That MPG is getting on I-75 and setting the cruise at 60 mph. That early Ford 6.8L V10 2 valve was pretty legendary for bad fuel economy. It doesnít show up in vehicles small enough for EPA rating much but a 2012 E350 passenger van with the more advanced 6.6L V10 3 valve is rated at 10 mpg city / 13 mpg highway. makes 6 mpg seem more reasonable in a huge RV

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Solar on top shouldnít add to much friction drag as compaired to a/c and emergency access mandates.
True. When I added solar panels to my current van I didnít see much of a fuel economy hit. (Mine are framed in 80/20 and set underneath a ladder rack) I do think it might disturb flow enough to make something like the Michelin top fairing worthless.
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Old 07-21-2021, 01:26 PM   #20 (permalink)
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Quote:
Are you talking about the front or the back of the box?
Front. In accordance with aerohead's suggestion, the 'inflatable' part was to fill the van/cab gap.

You last example has the overcab deflector already but no opportunity on the edges. It would need the doors reframed or padded out.

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