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Test Report: Towing the Bowlus Road Chief

Discussion in 'Model X: Driving Dynamics' started by jackbowers, Apr 12, 2016.

  1. jackbowers

    jackbowers Jack Bowers

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    I’ve got good news and bad news for those who have dreamed about towing a full-function travel-trailer with the Model X. First the good news: It’s possible. The Bowlus Road Chief pulls it off with a efficient combination involving ultra light-weight design, low height (6’4” interior headroom) and a compact aerodynamic shape. Now the bad news: it costs as much as a fully loaded Model X, and you will may have to wait almost 18 months to get one.

    Still, for those who appreciate good engineering, the Bowlus is as unique to the world of travel trailers as Tesla is to the world of automobiles. Its monocoque (stressed skin) structure, like most jets uses aircraft-grade aluminum and thousands of rivets to achieve high strength with low weight. The obsession with efficiency and weight savings extends to the living quarters too,which depending on your perspective has the feel of either a small luxury yacht or a large corporate jet.

    Checking in at less than 2500 lbs, the low weight of the Bowlus Road Chief has multiple advantages for the Model X. With a tongue weight of less than 200 lbs, it can be towed with the 22” performance tires set at 50 psi. Disconnecting the trailer at Supercharger stations without pull-through slots is fast and easy. If you’re in a hurry it only takes 90 seconds and in flat locations the trailer can be pulled by hand into a nearby parking space (the trailer’s brakes can be engaged and powered by its own 12V system). The Road Chief can be towed up most mountain passes (expect to consume 12-13 additional miles per 1000’ elevation gain, versus 8 additional miles for Model X when it’s not towing anything), and the trailer’s weight can be fully regened on downhill grades of less than 7% if the pack is warm (expect to recover 11 miles per 1000’ decline, versus 7 miles for Model X itself). Last but not least, in Ludicrous mode you can zip from 0-60 in about 5.5 seconds with the Road Chief, making lane changes less challenging relative to other towing situations.

    While low weight should make it possible to get over Donner Pass (charge to at least 95% at the Rocklin Supercharger), it’s only part of the battle when it comes to driving range. The dominate factor is aerodynamic drag. Because the Model X is heavily optimized with a Cd of less than 0.25, its range takes a significant hit when you tow anything that extends outside of its slipstream, especially if the item being towed has a poor drag coefficient. The Bowlus is a winner in this respect. Because it is narrower than Model X, less than eight feet tall,and relatively aerodynamic itself,the range hit is tolerable.By that I mean the Bowlus makes it possible to get around,not necessarily easy. Unless you are traveling less than 100 miles without much elevation gain, you’ll probably want to stay below 55 mph in order to benefit from the fact that aerodynamic drag goes up by the square of vehicle speed. Dropping from 55 mph to 50 mph, if you can stand it, will improve range by about 10%.

    How far can you go? Towing the Bowlus on highway 101 near Oxnard, on a relatively flat course with light wind and 60 degree temperatures, the steady-state power draw at 55 mph was about 540 Wh/mi. At 50 mph it dropped to about 485 Wh/mi. Model X has an EPA range of about 250 miles, which translates to about 340 Wh/mi. So, under ideal conditions (summer driving, no significant headwind) it should be possible to go 175 miles if you limit your speed to 50 mph.

    Fortunately, most Superchargers are spaced less than 125 miles apart, which means 55 mph should work okay even with a light headwind. Driving in the northwest a few months ago, it was not unusual to see Model X drawing 500 Wh/mi due to the combined effects of AWD with torque-sleep disabled and the heater running in 25-degree temperatures. But even then I didn’t find it that hard to get around; it just took a lot of extra time at each Supercharging stop.

    This brings up another advantage of the Bowlus Road Chief. Because of its airtight design and high-efficiency heating and air-conditioning system, it only needs the 120V 30A power connection at the RV park hookup, which leaves the 14-50 available to charge the Model X. You’ll want to limit the car’s charge current to 28A to avoid flipped breakers, but even at that rate (about 18 range-miles per hour) you’ll still get a full charge overnight.

    For camping where there are no hookups, the Bowlus can run on its high-efficiency 12V power system, which among other things powers its LED lights, a small high-efficiency refrigerator, and the water pump. There is an exterior 12V connector that can be used with a portable solar panel the charge the trailer’s 12V battery. While it hasn’t been tried yet, I’m guessing it will be pretty easy to make an adapter cable allowing the Model X’s always-on 12V accessory port to charge the the trailer’s 12V battery during cloudy/rainy days or in heavily shaded areas.

    There are other thoughtful engineering choices that Tesla owners will appreciate. The trailer has been designed with an 80-year service life goal, meaning that everything is accessible and replaceable, right down to the foam insulation in the walls. Convection-based ceiling vents reduce the need for A/C use. A reverse pressure ventilation system for the toilet eliminates the bathroom smell that is common with most RVs. The tanks are located inside the living space to avoid freezing during winter camping. The black-water tank is a compact hand-carry unit (like some European trailers) that can be emptied in public restrooms, eliminating the need for dump-station stops. The bottom of the trailer is a flat sheet of aluminum, and the monocoque design keeps the center of gravity very low.

    Driving 55 mph with the Bowlus in tow, you can almost forget that it’s there.You don’t see it in the outside mirrors, and it corners effortlessly just like the Model X. The trailer weight is less than half that of the vehicle, so acceleration and regen characteristics are not radically altered. You hear the usual ball-hitch clunking noises when accelerating and decelerating, but it isn’t as loud compared with other trailer-towing scenarios.



    Finally, a few thoughts on ordering a Bowlus Road Chief (which I’ve already done). The relatively long wait (currently just shy of 18 months) and the non-refundable deposit ($10k) are nothing to smile about, but they’re not all bad either. By the time Tesla owners start taking delivery, the Supercharger density may be twice what it is now, and a larger battery pack may be available for Model X. Both would make it easier to get around compared with today. I suspect the resale value for the Road Chief will remain high, because it’s built to last with high quality materials, and because any used Bowlus that’s available right away is probably worth almost as much as a new one you have to wait for. As for insurance, it doesn’t appear to be much of an issue. Liability goes with the tow vehicle, so insuring a trailer for theft/damage doesn’t cost much, even when the trailer value is high. State Farm told me the Bowlus would probably run about $500/year.
     

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  2. JimVandegriff

    JimVandegriff Member

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    Thanks for this informative report. We have been thinking a lot about trailers and what to pull with our X, with an important consideration (besides weight) being recyclability, and long-term use. Here is the link to the company's website for the Bowlus Road Chief: Overview - Bowlus Road Chief for those interested.
     
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  3. cmc5dc

    cmc5dc Member

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    Jack,
    Nice ride. What brake control did you end up using and if you installed it any step by step directions you could share?

    Carl
     
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  4. wts13

    wts13 Member

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    Thanks for the report. We're planning to tow our TrailManor with our 90D. Many of the things you said about the Road Chief will apply to the TrailManor as well - it's light (our model is about 3000lbs unloaded), short (6' 7" when collapsed) and should have a decent aero profile.
     
  5. AnOutsider

    AnOutsider S532 # XS27

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    I searched long and hard for a trailmanor (we ended up deciding that, for range, a pop up would be best, and I wanted hard walls), but couldn't find one. I guess they're not too popular on this coast.

    Do let me know how it goes! We ended up with a high wall popup, but I'm still open to hard wall!
     
  6. 7racer

    7racer Member

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    Great post and info!!

    It's great to see the X being used like this.

    First electric vehicle that can tow!!
     
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  7. AnOutsider

    AnOutsider S532 # XS27

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    The Rav4 and Model S would like a word with you.
     
  8. ohmman

    ohmman Maximum Plaid Member

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    Thanks @jackbowers. Wow. We discussed the Bowlus Road Chief in this other thread, and I've been drooling over it a bit. The consumption data is extremely valuable.

    I'm still leaning toward the Alto Safari Condo teardrop. It's not nearly as sexy, but it's also more reasonably priced. The weight is lighter as well. All of that comes at the cost of style and space, of course, so there's a trade-off. I'm really curious about consumption differences pulling the Alto.

    Tell us about Supercharging. Did you have to disconnect the 'Chief at each stop? From an inconvenience perspective, was it tolerable?

    Thanks again.
     
  9. EcoHeliGuy

    EcoHeliGuy Member

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    I'm interested in the regen portion. Was the X able to take advantage of the extra weight? Or was the regen rate same as an almost empty model X?
     
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  10. Boston

    Boston Member

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    Thanks @jackbowers. Great write-up. I am interested to learn about your overall experience travelling with the trailer. The Road Chief sounds like a perfect match for the MX but even so I am left to wonder if extended trailer travel is really practical just yet. Starting with 175 mile range with the Bowlus (60 degree temp, no hills, light headwind) it seems prudent to derate for average conditions which will likely include some elevation change, temperature and wind variation). Taking these factors into account I think derating to a range of 150 miles would be a reasonable average to expect. Trimming off another 15 miles to provide an "empty battery" buffer leaves a practical range of 135 miles.

    Travelling at 50mph this would require stops every 2hr 40m (with unhitch) and then a charge for 1hr (and re-hitch) yielding an effective rate of travel of 36mph. I am not saying this is a bad thing, just a difference from an ICE tow vehicle which averages closer to 60mph effective rate of travel and little need for "fuel planning/management." I cannot imagine things getting much better than travelling the country with an awesome trailer like the Road Chief and the MX. No incremental cost for charging at RV campgrounds and free SuperChargers across the country. I have managed to convince myself that it is possible but not particularly practical. I am looking for any wisdom that would help me switch back to the dream.
     
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  11. Eresan

    Eresan Member

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    Guys don't forget airstream Bambi. 16-19'. MSRP is $41k-$50k. Dealer always give 10-15% off buying new
     
  12. JamesG

    JamesG Member

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  13. JamesG

    JamesG Member

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    My X does not have an always on 12 volt power supply?
     
  14. jackbowers

    jackbowers Jack Bowers

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    Taking delivery on October 10th, so will have more to report once I get the chance to do some testing. Also planning to switch to 20" wheels and get 100 kWh pack upgrade when it becomes available. In theory those two changes should boost range about 25%.
     
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  15. ohmman

    ohmman Maximum Plaid Member

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    When did you order, @jackbowers?

    Your original post in this thread was April 12th, but I get the feeling you already had an order if they allowed you to test one out of Oxnard. Just curious about how realistic the 18 month lead-time is.
     
  16. jackbowers

    jackbowers Jack Bowers

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    The Bowlus folks created a special Lithium+ version (considerably more expensive) and allowed me to purchase the first one built as I think they are looking to get feedback on how it works with the Model X. Along with several other new features, the Lithium+ version features an upgraded electrical system with 3-4 kWh of 12V battery capacity and a 2 kW inverter that can run the Microwave and/or air conditioner off the 12V system. There's also an outside 120V outlet that can (in a pinch) slowly charge the Model X (driving on flat ground at low speed you could probably get about 7-8 miles of range out of the trailer's battery). The Model X also charges the Lithium+ pack through the 7-pin trailer port when the car is on. At about 2400 lbs, the weight of the Lithium+ version is only slightly more than the standard Bowlus.

    I picked up the Bowlus Lithium+ on Monday and drove it from Henderson back to Reno (through Death Valley) Tuesday and Wednesday. As full-function RV trailers go, it is state-of-the-art when it comes to light weight and cabin energy efficiency. Other than a problem getting the Model X to recognize and send power to the trailer lights (which we were able to work around by first sticking a port tester in the 7-pin socket), everything worked flawlessly on the trip. The trailer attracts a lot of attention, so you have to spend a lot of time talking about it, but that's nothing new for Tesla owners!

    My main concern for this trip was towing range. While towing a trailer with the Model X is no picnic, things turned out better than I thought. The power draw on uphill mountain passes can be breathtaking at times, but you get full regen recovery on the descent (no braking was necessary even on 10% downhill grades), so the overall average is generally good enough to go 100 miles with much range anxiety (provided you start with at least 225 miles on the pack). Driving 55 mph on a flat course at 70 degrees F you can expect around 475 Wh/mile if there is no headwind, so with a fully charged 100 kWh pack it would be possible to go 150 miles under the right conditions. But it takes about 12 extra miles of range for each 1000' gain in elevation, so if your ending elevation is higher than your starting elevation the range can be significantly less.

    In the spirt of testing the limits, we drove through Death Valley, charging full overnight at Furnace Creek then topping off to 225 miles at Stovepipe Wells. Going Southwest on 190, we proceeded up that 5000' 8-9% grade. It was early morning and no one was behind us, so I slowed to 40 mph to keep the power draw under 100 kW. Over the next 13 miles we went through 83 miles of battery range, averaging 1500 Wh/mile. But the rest of that leg was uneventful, and we made it to the Lone Pine Supercharger with 41 miles showing. Lone Pine to Mammoth also looked a little tight due to the 4700' elevation gain, but starting with 235 miles, and driving 50-55 mph we arrived with about 35 miles.

    One other pleasant surprise was that Trip Planner seemed to figure out the trailer's characteristics and after several hundred miles it was doing a decent job of projecting our battery range at the next destination. You can even see the projections with or without the trailer by toggling in and out of trailer mode.

    Will have more to report as I try out more things. Next trip will be Reno to Spokane late next week.
     
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  17. ohmman

    ohmman Maximum Plaid Member

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    I had the opportunity to meet up with @jackbowers today and view the Bowlus in person for myself. Wow! The trailer is truly a stunner. While Jack was busy at his speaking engagement, I watched as numerous people walked over just to look at the trailer. I spoke with a few of them, and the feeling was unanimous - this was one impressive looking camper.

    I found that the interior space is much larger than it appears in photos. It's also surprisingly roomy considering the exterior dimensions (width, particularly), and just how compact it looks overall. I think the tapered tail has a lot to do with that - you fit the whole "bedroom" back there, which leaves the rest of the high-roofed area for living space. The craftsmanship was apparent, and it seems to be very well thought out.

    Overall, I was very impressed. Jack mentioned that the shiny aluminum finish scratches easily, and that the AC occasionally has a difficult time keeping up. Though, that situation was in Death Valley. Minor complaints overall for an impressive vehicle.

    @jackbowers is going to attempt Donner Pass tomorrow. As he says, it works out on paper. He seems to have a good backup plan, but I'm hopeful he won't have to use it. Looking forward to hearing the update, Jack. And thanks for your time today.



    IMG_3592.JPG IMG_2961.jpg IMG_2962.jpg
     
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  18. JimVandegriff

    JimVandegriff Member

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    Beautiful, functional trailer. Thanks for the pics and report. After re-reading this thread my wife and I are struck with how similar our conclusions about range, speed, and elevation effects are to jack bowers' in our Airstream Bambi. What a special trailer this Bowlus is!
     
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  19. qadaemon

    qadaemon Member

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    Thanks for the pictures; the Bowlus looks amazing.
     
  20. jackbowers

    jackbowers Jack Bowers

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    Happy to report that getting around with the Bowlus continues to be easier than I thought. Yesterday I drove Rocklin to Truckee, which involves a 7000' elevation gain climbing up Donner Pass (Donner Pass to Truckee is downhill and you can do it on regen alone). It took 190 miles of range driving at 55 mph with climate control off. The temperature was 50s and I have 20" winter tires filled to 46 psi (the Bowlus tires are at 50 psi).

    I'm also finding myself driving 65 mph in places where the Supercharger density is high (note: in California there's a 55 mph limit for cars towing trailers). If there isn't much wind and the elevation is relatively flat, the energy draw is usually 550-600 Wh/mile at that speed. You do get some sway if there's a crosswind, but the Model X has anti-sway built into the traction control, and it seems to work pretty well. Another interesting thing is the trip planner has gotten to know the trailer characteristics pretty well over the last 1000 miles, and it now does a good job of projecting the battery range (you can toggle in and out of trailer mode to see the projected impact of the trailer).
     
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