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Old 12-20-2012, 07:50 AM   #1 (permalink)
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UK RV'er seeks inspiration...

Hi,

short term lurker. Owner of a 33' long 11' high 7.5 ton (16,500lb) motorhome / RV thing.

Aerodynamics of a brick, slushbox auto, 6 litre straight six turbodiesel, 175bhp, old skool bosch diesel pump (so can run on veg oil) 1996 build - costing the original owner 150,000..... Already done a rear diff swap for the highest possible ratio available - now tops out at 80mph (yes).

Plans include:-
front air dam - any ideas as to what front approach angle I should go for?
Cover rear wheels
Belly pan?s
Boat tail, with foldable sides on pneumatics for tight spaces.
cameras instead of mirrors - this has just been made legal in the UK this year or possibly the 'hang out the front' type you see on inter city coaches

currently getting 11.5 UK mpg (our gallons are slightly bigger 1 ukg = 1.2usg) and our fuel is 1.45 per litre = 2.36 dollars /litre = $8.94 a us gallon...

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Old 12-20-2012, 08:38 AM   #2 (permalink)
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Welcome to the site. There are a couple other RV owners around here. I'm sure we can help you bump your milage up a bit.

Have you looked over the 100+ Hypermiling / ecodriving tips?
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Old 12-23-2012, 07:21 PM   #3 (permalink)
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Hi - yes I have looked at both the 100 and the 65 tips pages. driving such a big vehicle and the state of the UK roads does negate quiet a lot of the tips sadly - unexpected / unseen stops, seriously bad driving (tonight I followed someone doing 30 - 35mph in a 60mph area, and slowed to 20mph for any and all bends - pity I was in a hurry to get home to help the mrs go xmas shopping)

the UK is a lot smaller than the us (really? ) and as such the roads are very very heavily congested in most of it. luckily, I live in a quiet area, which helps.

Road testing for mpg / coast down / tuft testing is not really practical here - I live 25 miles / 1 hours drive (due to the wiggly coastal road) from any motorway (interstate?), and nowhere in between is there any big road - its all single carriageway.....

How does tuft testing work on large vehicles with a leaf blower? The reports I have read on here are about small cars, not dirty gert RVs.

Thanks for the intro - heres hoping eh?

Guy
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Old 12-23-2012, 09:25 PM   #4 (permalink)
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I'd say that using a weight scale (as do the truckers) to see where the bus lives would be good start. FF/RR bias, Port/Starboard bias and any corrections needed. Proper tire pressures obtained as a result of certified weight scale tickets, also.

I might look into pre-warming the fluids: coolant, engine oil, maybe trans and axle oil with electric heaters.

Establishing a very high bar for maintenance (mechanical baseline) is worth more than most "mpg mods" as it directly affects reliability & longevity.

Really, for RV'ers here and elsewhere the idea of "economy" has more to do with how many nights one is aboard. And the distances covered annually. Vacationers really don't travel that much in comparison with those who live aboard.

And for those who live aboard (full-timers) the distances may not be that great either. Really, the "economy" can come down to not owning a house or paying high rents over long periods of time.

Situations differ so much that rules-of-thumb may be hard to come by.

But the best reading -- this is Ecomodder, after all -- will be of all threads by Orbywan in his pursuit of aerodynamic improvements on a Class C motorhome.

Welcome!!

.
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Old 12-27-2012, 11:37 AM   #5 (permalink)
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Thanks - I have spent a while reading about orbywan and aero-rv.. Surprised to see the little effect the under body smoothing made.

To this end, mod #1 has been done today. In the pics attached, you can see the covered rear 'duallies' (sp?). This was quite easy, as I have some foamalux ultra (a sort of hard board skinned plastic, often used for signs and wipe down surfaces in kitchens). This I simply cut to size, and using self tappers, screwed it to the fibreglass body. Obviously, I pumped the tyres (note correct spelling) up to the max my compressor will do - 105psi - and thats still under the max sidewall of 110psi.
the bottom edge was wobbly, so has been stiffened with an ally 'hockey stick' bit.

In the other pictures, you can see my super aero wipers, and wing mirrors I want to send as much air round the slippery sides (again, in one of the pics) not the lumpy as hell roof, with 5 roof vents, and three skylights.

any ideas for the wipers? Cameras have been ordered for mirror delete option - only legal in the UK this year (2012)

Back end is ripe for a semi boat tail - I think I am going to make it foldable, as the overhang is already gigantic. The back face gets filthy, whereas the sides stay pretty clean. I have some sheets of ally kicking about, and some ally angle. Not sure if I should put the bot tail on a pneumatic retract system (again, I have some pneumatic rams) - which would be very cool, but quite difficult to do all three? at the same time. Any suggestions for a self folding mechanism would be appreciated. I dont need to access the door at the back very often, I think the boat tail would be default out, press button fold in.
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Last edited by guyd; 12-27-2012 at 11:44 AM..
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Old 12-27-2012, 11:50 AM   #6 (permalink)
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I wouldn't worry about removing your wipers. I wouldn't think that they would be as bad on a flat front as they would be on a car where the air is flowing from the hood over the windshield. If you do choose to do something, a cowl would be fairly easy to fabricate. It would also keep your wipers good longer by keeping the uv rays from deteriorating the rubber as well as keeping road grime off them.
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Old 12-27-2012, 11:54 AM   #7 (permalink)
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after looking at your wipers again... it would have to be a very big cowl! might do more harm then good? You could delete your passenger side wiper and put a longer straighter arm on the driver side? that would keep it down lower to where a cowl could be made smaller.
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Old 12-27-2012, 05:47 PM   #8 (permalink)
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Quote:
Originally Posted by guyd View Post
any ideas for the wipers?
If you couldn't delete both, a single-wiper would be a good attempt, preferably if the wiper remained stand-up while not in use. BTW I've once seen a wiper-less windscreen which used air jet nozzles to wipe it.
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Old 12-28-2012, 11:28 AM   #9 (permalink)
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The rv is 8 feet wide, but 11 feet tall, so more wind is going left right, than up, so an upstanding wiper next to the A pillar would be worse than where it is, unless you are suggesting one in the middle? Ill have a look at the wobbly wiper system mercedes use?

Cameras arrived this morning, and been tested on a old computer monitor, with an iScan pro upscaler which ill use to quickly adjust contrast and brightness to compensate for bright round town or dark country lane use.
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Old 12-28-2012, 11:53 AM   #10 (permalink)
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I like the compressed air idea. You would have plenty of room for a decent sized air tank. Using a cheap paint gun for a nozzle it would give a nice wide spray pattern. Does the RV have airbrakes or air ride by any chance? most of the city buses here are squatting so they have air ride, not sure about brakes though? would be easy if you have the compressor already.

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