elpatu

Hi all !
Many of you asked about bike caravans so I'd like to post my own project called "El Patu".
It took me a little more than two months to build it and it weighs about 62 kg (53 kg without the solar system - solar pannel, solar charger, addumulator and inverter). The main ideas of the project are:
- cabin made out of wood and fibreglass to make it leightweight and "nice" in the interior (avoiding also problems of humidity thanks to the wood)
- foldable front part to make it shorter (it's "only" 180 cm including the hitch, when unfolded you have a comfortable bed size of 204 x 77/68cm)
- electric bike to compensate the additional weight (Stromer ST1 "Mountain" with 30 Nm)
- solar pannel on the roof (120 Wp) in order to charge the bike during the trip (and be independant)
Since there are many aspects to such a project (wheels, hitch, materials, solar pannel, accumulator etc.), I decided to create a website in order to document the building process and explain the details (also with photos): elpatu.weebly.com (El patu - bike caravan - Home)
I would appreciate your comments - maybe you have your own ideas about how to build such a bike caravan "in the best possible" way so I'm very interested in your opinion and hints.
Thanks and greetings from Switzerland!
Marcel

rifraf

Hi all !
Many of you asked about bike caravans so I'd like to post my own project called "El Patu".
It took me a little more than two months to build it and it weighs about 62 kg (53 kg without the solar system - solar pannel, solar charger, addumulator and inverter). The main ideas of the project are:
- cabin made out of wood and fibreglass to make it leightweight and "nice" in the interior (avoiding also problems of humidity thanks to the wood)
- foldable front part to make it shorter (it's "only" 180 cm including the hitch, when unfolded you have a comfortable bed size of 204 x 77/68cm)
- electric bike to compensate the additional weight (Stromer ST1 "Mountain" with 30 Nm)
- solar pannel on the roof (120 Wp) in order to charge the bike during the trip (and be independant)
Since there are many aspects to such a project (wheels, hitch, materials, solar pannel, accumulator etc.), I decided to create a website in order to document the building process and explain the details (also with photos): elpatu.weebly.com (El patu - bike caravan - Home)
I would appreciate your comments - maybe you have your own ideas about how to build such a bike caravan "in the best possible" way so I'm very interested in your opinion and hints.
Thanks and greetings from Switzerland!
Marcel[/QUOTE]

G'day Marcell,
thanks for sharing.
Dont envy you any windy days.
I towed a Carry Freedom Y-frame trailer with a 90 litre plastic "box" on it and it was murder at the slightest hint of a head wind.
Didn't stop me from my trek across Australia East to West, but I'd do it different next time.

alan s 

It would be a little more aero if you pulled from the other end. Also, maybe want to add a way to tilt the solar panel up to get a better angle to the sun. Does it have air conditioning?

elpatu

Hello Alan, thanks for your comment. It's true that it would be a little bit more aerodynamic the other way around (and actually I was thinking about this possibility almost till the end of the project), but for me, aerodynamics was not a very important concern: aerodynamics are important a higher speeds (especially because it increases exponentially), but not at the speed I think that I'm going to travel (about 15-20 km/h, I guess). For the solarpannel: I first wanted to make it flat (so that it would receive the same amount of solar energy from all directions, which means: not really a maximum - for that pannel should be in an ideal angle to the sun - but a good average). Unfortunately, the caravan didn't look very nice with a flat roof and was too high in the rear part. So, I decided to make the solar pannel go down to the end. This now means that the energy you can harvest depends on the direction you are travelling: if you have the sun in your back, you're fine; if the sun comes from the side or from the front (worst case) you get less or no solar energy ... And no: no air conditioning!

elpatu

Hi rifraf, that's true - winds are a concern ... So, for some trips (near the sea for example) this caravan is not a good choice. In Switzerland, instead, and many other countries in Europe, I think that it's ok - unless there's a storm or something like that. Don't have much experience with the caravan untill now (just finished it last week), so I certainly can tell more once I've travelled a little bit.

antokelly

Wow thats loks fantastic sturdy well built ,great idea on the electric bike .
i can see strong head and side winds being a chore to cycle but yeah its still is a classic idea best of luck with it hope it works out.

anto.

Darth Lefty 

Sweet idea!

I just took a look at motorcycle pop-up campers and they weigh 100+ kilograms so you are doing well with yours.

Juha

Thanks for the pics, elpatu, and welcome to BF. Congrats, it seems like a nicely built project!

Out of curiosity, what got you started with this? What do you consider as main advantages of the caravan compared to simply camping (I can think of a few, but would like to hear your take on it). Your design seems to share some characteristics with the Danish Wide Path Camper (Wide Path Camper - Wide Path Camper Webstore).

--J

MassiveD

I think you have a really nice design there. The main issue is the weight. The weight as it stands now is in the range I would consider as an occasionally moved structure. If one had a canal say, where there were campsites every 20 miles (or whatever suits a particular user), and one could spend a day or two, or a week, then ride a path to the next spot, this would be a good design. But as a substitute for a tent that weighs 2-10 pounds, it can't compete.

Of course there are some economies. You have enough space there that you would not require panniers, or rack (whether one chose to use them or not). It might be more comfortable in the trailer, and that would allow certain modest economies in bedding weight, etc...

I still can't avoid thinking that for my uses the trailer is overbuilt. I build boats and my 24 foot trimaran is made of 1/4 inch ply for the most part, and the floats are made of either 3 or 4 mm ply depending on whether one wants to venture offshore. 3mm ply is 10 pounds a sheet. Even with glass that could be around 14 pounds, and only a few sheets are required. Cerroplast is another option, though not as sturdy.

Anyway, nice trailer. Some of the folks over here:

Teardrops n Tiny Travel Trailers ? View topic - Bicycle TEARDROP TRAILER

Might get a kick out of it. I thought there was more bike trailer talk over there, but mostly it seems to be about bikes for use with teardrop trailers.

MassiveD

I was going to post a few camper links to Youtube. I had looked pretty carefully and reallt only saw one project that would be even semi viable for "real" touring, as opposed to a very different approach, more snail like. Have to say though, there are now a lot of very interesting projects, for the most part in the snail category, but still some very interesting work is being done.

OK one:

https://www.youtube.com/watch?v=mWnsu4dfNGs

mtnbud

Did you see this one by Paul Elkins?

PS - I like the foldable front on your design Elpatu!

BigAura

Nice work & cool engineering! But for the type of touring we're interested in on this site it's way too much of a heavy burden. As others have pointed out our sleeping systems are as little as 1kg and hardly ever more than 5kg.

I think you should look at much lighter weight materials than fiberglass & wood. A Pop-up and/or fold-out style would give you a much more aerodynamic profile.

Once again, I do like what you've done.

MassiveD

Yeah, I have seen Paul's work. That airstream inpsired one you posted was too big to my way of thinking. Too much wind resistance. At the light end of the spectrum it is tough to get anything that is reasonably aero, and yet has enough space inside to be comfortable and well aired out.

elpatu

Thanks antokelly - we'll see tomorrow if it works (planned to go out for 1-2 days if the weather isn't too bad). And as I said earlier: yes, wind IS a concern! ;-)

elpatu

Thanks for your comment Juha. Advantages of a bike caravan in my opinion:
- you don't need much time to install it
- better when it rains (we all know that it's no pleasure to travel with a tent when it rains ...)
- all your stuff is nicely organized thanks to the cupboards (and you don't have to pack it in and out all the time)
- you sleep on a good (more or less;-) matrass and not directly on the ground (better when it's cold, less insects ...;-))
- you definitely get some comfort (nice lights, electricity supply ...)
- you don't need a chair (you can sit in the entry or inside the caravan (when it rains)
- it's just fun and cool ... and you get in touch with a lot of people ;-)
Now the downside:
- it's heavy and relatively huge (you'll be slower and have to be careful in the traffic, hills or mountains can become very difficult ...)
- only for good (= asphalted) roads (so you can't do an real "outdoor trip")
- it's only for one person
- people stare at you (as if you were an alien) when you pass by (if you don't like that ... ;-)
But for me it's not "either tent or caravan" but "both of them": if you want to go to the mountains and off road, of course, you WON'T take the caravan. But for a nice trip along a lake (= mostly flat) it can be a very nice travelling option in my opinion. :-)

My main ideas come from:
- Wide Path Camper (for the foldable part)
- Project "Maus" (for the design of the cabin - at least at the beginning)
- Marissa Mullers cross country challenges (for the solar pannel and charging on the road)
(you find the links to all those projects on my page)

elpatu

@MassiveD: of course, a bike caravan is no substitute for a tent (and this is, in my opinion, not the idea as I explained in my answer to Juha: every option has it's advantages and disadvantages). Actually, reading your lines you sound very sceptical to me and mainly because of the weight. So let me say this: weight - in my opinion - is not that much a concern! I personally drive a Velomobile (a Go One Evolution) and it weighs around 55 kg (with electric assistance). In the meantime, I've made thousands and thousands of kilometers with this vehicule - no problem! Or let me give you another example: a german named André built a trailer that is around 60 kg (see here: André on Radtour) and he travelled hundreds of kilometers with it - WITHOUT HAVING AN ELECTRIC ASSISTANCE (personally, I would never do that ... ;-)) It all depends on how fast you want to travel and how far you want to get each day. I'm sure that with "El Patu" you can travel to the polar circle and back - you just need enough time to do so ... ;-)
A last point about weight: several persons have been talking about winds. Now, in relation to that I consider that the heavier the trailer is, the less it will react to winds ... ;-)

Thanks for the youtube-link: a very cool project by Sakari Holma (who also makes bikes out of wood). For me, personally, this is too small, which means: to low and too long.

elpatu

Thanks mtnbud: yes, I saw this project and it's one of my favourites because of the material Paul Elkin uses. It's something between "tent" and "wood". So lightweight an quite strong at the same time. Nonetheless, there were two negative points for me with this material:
- it's quite strong but not that strong (you can't really lean agains it for example)
- it has a serious concern with humidity!!!!!
In one video (don't have the link unfortunately) you see him after spending a night in a shelter built with this material - an the door (and probably the inside also) is all wet ... ;-) That's really not good (because with humidity you get a lot of other concerns very quickly ...)

antokelly

elpatu your desigh is perfect for going on tarmac from one campsite to another cycling the midi canal sure what would be better.

gorshkov

It's actually more aerodynamic the way it is. Turning it around will place a larger vertical surface at the back, which will cause enormous vortices from the air coming around the sides. For subsonic speeds, the best shape is rounded at the front and tapered at the back. Also, because the bicycle and rider are directly in front of the trailer, the shape of the front is far less important than the shape of the back. Probably the best way to improve the aerodynamics without a complete re-design would be to round off the corners.

I did notice that the taillight on your bicycle is pretty useless with the trailer - do you have lights and/or reflectors on it for riding at night?

alan s 

You'll get much better laminar airflow with the tapered end in front, which, for example, is typically found in cars. A truck plowing through the air creates a huge amount of turbulence and drag.

mtnbud

I'd be concerned also. I didn't see any accommodations to prevent condensation build up in Paul Elkin's design. I was also wondering if it was totally waterproof. There'd be no point in having a trailer if it leaked in a rainstorm. Paul Elkin's is quite the engineer just the same. He's got a lot of cool projects out there.

I have a camping trailer (aka caravan) and I have to leave a vent or two cracked open to prevent condensation. It's a lot bigger space than a bike trailer, so I'd think condensation could be a big problem. I'd bet you could easily add an rv vent to your design if you discover you have an issue with condensation. If not, open up a small hole or two in the wall and put a curved cover over them so they're only open to the air from below. Something like this.

elpatu

Thanks alan s and gorshkov for your explanations about aerodynamics. I'm not a specialist but I know from the Twike Project (TWIKE - Home) and from the Go One Evolution (velomobile that I drive) that the rear part is more important than the front part. And it's good to know that - although the design of El Patu is not optimal - it was a good decision to tear it from the front (and not the other way around).

For the lights: yes, the taillight of the Stromer is useless (since coverd by the caravan/camper), so it is mandatory to install electric lights at the back of the caravan if you want to travel by night (during the day, the reflectors I installed are sufficient). Of course, I'm going to install electric lights (just didn't have time untill now ... and for the moment I'm only going to travel during the day;-))

elpatu

Thanks, mtnbud, for your ideas about condensation / humidity. The "strategies" you mention to overcome this problems are good:
- open windows (that's why i installed the top window, which you can leave slightly open)
- active ventilation (I was thinking about that - and if humidity turns out to be a problem I will not hesitate to install one)

For me, the best way to prevent condensation is actually the wood because it can absorb a lot of humidity (that's one of the two reasons - a part from the aesthetical aspect (wood is nice;-)) - why I accepted the additional weight). In my opinion wood is one of the best regulators for humidity and effectively prevents condensation. But, we will see if it really fulfills those expectations in the practical test (I will tell you more about that as soon as I know more - now, in autumn / fall it's the best time to find out ... ;-)

elpatu

Hi there,
In the meantime, I made my first trip with the caravan. You can find the details on my page (El patu - bike caravan - Home, click on "diary"). It was a nice trip of two days to a lake nearby (at 27-28km, so I made 55 km in total - without charging the bike during the trip). There where also some climbings and I could make my first experiences with humidity also ... ;-)
For me, everything worked fine except the coupling system (which got lose twice and it also moves a lot and doesn't seem solid enough to me ...). So if anybody has an idea about how to improve that you're welcome. Of course, it'll also be a pleasure to answer your questions if you want to know more about certain things.
Greetings from Switzerland,
Marcel

BigAura

Interesting. I still see weight of your building materials as a huge stumbling block. I think you need to weigh each component and see if there is a lighter-weight option. Keep all your weights in a spreadsheet so you can play with options, such as how much weight would I save if used plastic hatch hinges instead of metal.

You might what to look at this Surly trailer hitch as an option or for inspiration: