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That sounds really, really cool. I guess you know that with kids, you might want fail-safe mechanisms that you wouldn't necessarily bother with if you were hauling 150 lbs of groceries. Getting something that you would feel confident going down, say, Pocussett Drive Trail, wouldf be something. You have a background in engineering? I saw a guy on the GAP with a DIY triplet in front with a tandem trail-a-bike in the back. Him and 4 kids.

I'm a fake engineer, a computer one ;) Hoping the cool factor inspires some folks who really have their own priorities to think about it... I like to think I have reasonably good thinking skills to fall back on once I see things fail, but at the start I'm going to get EVERYTHING wrong because I've never built anything (well, outdoor structures out of pressure treated lumber, but that's it). Pocusset trail drive is obviously be a nice connector for me in my current situation if that can stay open, see other threads. But I'm hoping the passive breaking is good/reliable enough to use generally (won't be taking it to Negley, but being confident enough going down Murray is an absolute must, and confident enough going down Greenfield avenue is a colossal plus).

My experience with a tandem trail a bike was bad. Bad enough to never want to use on again. How old are your kids? For the money it would cost to build a motorized trailer with seating for three, you might better off with something like a Madsen that you convert to an e-bike. http://www.madsencycles.com/ Sounds like an awesome project!

I have to say I don't think the throttle/brake coupler is well-thought-through. Think about what happens when you go over a bump, or the trailer does, and it starts braking/accelerating. Or when you go around a corner and the trailer decides it has to speed up as the bike pulls the trailer around. The trailer would push the bike sideways. To replace a car, the most successful option seems to be something like a bakfiets. Kids in front, where you can keep an eye on them, and I guess the handling works out. But still, it's your project, and good luck with it. (Also: if there are two wheels on the trailer you either have to power them both or just one. If you power both you need a differential -- which is heavy and complicated -- otherwise it won't want to do anything but go straight. If you power one I think you're always getting pushed to the other side.)

The trailer is the primary need, the tandem the (very) nice to have. I've looked at the madsen (I've looked at a LOT of things LOL). Am hoping for something I'd get more years out of with the kids (which also probably rules out the surly big dummy with a hooptie, otherwise a strong contender) and be able to carry more irregular and heavier things with.

The behavior around accelerating/decelerating esp around corners matters a lot obviously. My general feeling is that very quick feedback and action on that minimizes forces which in turn minimizes potential safety issues, esp if the braking is very responsive (the trailer should never be pushing the bike except for such tiny fractions of a second that it doesn't matter much). I'm much less concerned with efficiency issues around bumps or making the throttle as responsive acceleration-wise because a jack-rabbiting accelerate/brake cycle would make this thing a non-starter. A single connected system would still be preferred most of the time when I'm primarily just transporting people (yet another reason for the tandem), but the need to be able to haul is the primary one at first since it can encapsulate both and potentially covers more weather conditions and the trailer lets you vary the bike independently and couple and decouple at will, which is not a small plus.

I am not an engineer, so YMMV.. The brakes that are readily available and that could quite possible work for the trailer application that you described are called "surge brakes". I think that you could also fab up something that would work in the opposite direction to apply pressure to a throttle controller of some sort as well. But... mechanical failure in the case of surge brakes on a trailer being towed by a bicycle would be.... bad. I recently towed a few junk cars using a tow dolly that utilizes surge brakes. The brakes failed, unloading the weight from the tongue during braking (it actually levered the rear end of the truck off of the ground. This caused my truck to be pivoted on the front axle. An adventure for sure. The design of the tow dolly requires brakes, so I know that the situation would be different with your trailer, but you know what I mean... The trailer providing propulsion might prove to have the same limitations... pushing your back wheel off the ground under power. Im sure that there are ways around this, I'm just not sure how difficult/expensive/reliable the whole thing would be. Again, I am no sort of engineer. Good luck, let us know how it goes!

What about something like this electric assist bakefiets? http://bakfiets.nl/eng/accessoires/cargobike/long/elektrisch/ Wondering if you could retrofit an electric assist system to a similar bike more readily available in the U.S. I know thick bikes had a cargo bike that looked kind of similar-ish.

I have a 10 and 8 year old in a Madsen, and if they ever finish up the weather cover, this thing will be pretty sweet for winter use. You can score a DIY e-bike conversion for a Madsen around a grand, which puts you around $3k for the whole thing. You'll spend a lot more than that building that trailer.

3K in is a lot right now, actually anything more than about 1500$ is. So that makes just about all the ready to go options a tight squeeze or impossible. But if you don't mind if I test ride the Madsen, preferably with the kids, it'd be good to get some actual data points rather than just flying off on this thought experiment. High level I'm guessing I could haul the three kids to school because it's flat-ish, but just about anything else involves a bigger hill and would involve unloading them before the climb. In terms of concerns about up/down pitching depending on centering of the load and acceleration/deceleration... I don't know if it's feasible, but I prefer designs that are stable without the bike to simplify loading/unloading. Most preferred of these would be three-wheeled design with fixed forward freewheels in back and a front wheel able to turn laterally in the direction of motion (which relies on the assist not being too aggressive obviously), and pulling the trailer directly that way. Bonus is that if you can do this then the hitch arm becomes a "point this way" steerer and you have a very, very crude low speed electric vehicle if the bike breaks down... theoretically and subject to a bunch of caveats about dimensions, having a place to sit or squat, and having something more secure to hold onto. Right, so I want it all, for nothing, and that's not realistic. But what are the real trade-offs and why?

I should dig up the picture of the bike my great grandfather Charlie of welded together, mentioned in the Bike History thread. I do have an old 2-person trailer in the back of the garage somewhere. It was pretty beat up by the time I (or rather my kids) finished with it though. I have no sense that automated boost or brakes would be a good idea -- my experience when we switched to a ride behind was that from time to time I would have to yell "stop pedaling" when I needed to stop going up hill or Innes would jackknife us, and that was with a relatively high-gain feedback loop between a human being and a (sometimes daydreaming) other human being. I suppose you could pull the tandem trailer behind a ride behind, but I really don't want to think about that. In all honesty, I think that really low gearing is the way to go.

Really low gears on a cargo trike is probably one of the saner things I've thought about. In pair or not in-pair with electric assist (probably front wheel hub motor). The trouble is finding something with enough cargo capacity (not so much weight, but room for three kids to not kill each other is tough). Once I need another trailer anyway, I kinda fail to see the point. And width is also a major concern if I'm going to try and be rigging together something that CAN be used on a Costco run, though that sidewalk is just so narrow maybe I need to ride the bridge in lane (aghhh)... but, perhaps foolishly, holding out hope with small wheels and battery weight below wheel axles....)

Dude, just get this: or this: and modify the gearing. You can add electric-assist if you want. Job done. (http://www.mcmaster.com/#bicycles/=u5fy84)

Oh, I'll do one better: I mean, I'm seriously tempted here, but between new gearing and brakes a some kind of seating/enclosure and mounting that truly securely it's still quite a project. It just seems to me like the auto-brake, auto-throttle trailer is such a compelling idea... was hoping to find someone else who thought the same way I did.

Also, handling. Once you get to front loaders, I don't really know how suitable a road going vehicle you can say you have anymore.

Schwinn meridian adult trike might be able to be modded somewhat. They run $250 at wally world. Some folks even sell a pre-modded version: http://www.savannahebikes.com/schwinn-electric-powered-3-wheel-adult-tricycle.html

My wife had Iron City Bikes put an e-hub on her bike in 2009 and it works well. It can give her something >300W assist (of course it is heavy). It seems to me that getting the drive assist on the main drive wheel of your bike makes sense. It might be possible to do that near your price point these days -- I'm not totally sure.

You will spend over $1500 on the trailer project. Easily. Not to mention time. The Madsen can sit 4 kids, but things are mighty slow after that. Two is OK, but I'm glad I don't have a lot of hills on my typical routes. There is a chance I'll be moving up a hill soon, might think about an e-assist myself if that happens.

Well, the passive braking mechanism, which I consider the lynchpin of the big trailer thing generally doesn't have to be expensive: http://appropriatetechnology.wikispaces.com/Bicycle+Trailer+Hitch+Braking+System In terms of attachment to the bicycle I don't much like what they have, and would want to see if something is buildable without two much complexity that can be secured to the rear of bikes both down at stays/rear axle level and at seatpost level. Simplest thing I can think of probably relies on the eyelets and then bolts to secure around the seatpost as well. Would probably wind up looking something like a rear fender built for the apocalypse. But anyways, right, after the braking, attachment to the bike and framing version 0 of a trailer, I can tinker with overall design parameters much more freely and would plan to do so for a while till things felt right before building in things like kids seats... maybe. If I can even get started.

I was riding the GAP trail once, carrying sleeping bags and a tent on a single-wheel trailer attached to my rear hub. Things were OK until I came down around the Pinkerton trail detour and couldn't control the thing coming downhill and around a curve back onto the trail. I think you're going to experience something much worse every time you go downhill and around a curve. On the plus side, you have this homemade surge braking system. On the down side, you're planning to attach the trailer at your seatpost, giving it much more leverage than my trailer had at the hub, you're probably going faster than I was on the trail detour, and you're carrying a much heavier and more precious cargo. Every time you go around a corner the trailer is going to want to keep going the direction it was going, and it's going to have a lot of sway (literally) over the direction of your combined system.

They make kits for motorcycles to allow using a trailer via a car-like ball hitch I would like to see something similar made for bicycles, only lighter duty. I think this would be superior to the attachment schemes of most bike trailers since it would attach to the strongest part of the bike (the frame), and it would keep the trailer "centered", not off to one side like some mechanisms. It would keep your center of gravity low, and the ball & socket has the necessary range of motion and locking mechanism too. It might weigh a little more, but you are pulling a trailer... whats two more pounds?

I've thought about this and while I could write out my thoughts in detail, I think this is the bottom line: 1) Attaching a trailer of any real weight at the seat post is a bad idea for exactly the reasons Jon stated in his last comment. 2) A functional self-propelled trailer would be extremely difficult to cobble together, and in any case would be problematic for the reasons many have noted. That such a thing is not known to the automotive world should tell you something. 3) While in theory you could engineer a hydraulic surge brake setup for a bike trailer, it would be a massive challenge to build it, and a second massive challenge to make it actually function as intended. 4) If you wanted to haul kids on a bike trailer, it would be relatively easy to add a brake system to a custom-fabricated trailer and give them their own brake pedal. As long as they are as trainable as a good beagle, they can press on their very own brake pedal at your command. 5) The easiest way to accomplish what you want is probably to buy a bike that (a) can be converted to an electric assist rear wheel; (b) will allow massive downhill MTB brakes to be bolted on; and (c) has a steel frame to allow for easy welding of a trailer hitch connection near the rear axle. I would forget about self-propulsion and passive braking and just build a bike that goes and stops with authority. (6) A modern, no-suspension, steel-frame mountain bike with disc brake mounts and potential for aftermarket e-assist seems like the best choice. Then couple a trailer to it with what is called a "high misalignment" rod end. You can find them and the accompanying weld-in tube ends over in race car world. 7) I would be happy to fabricate a heavy duty bike trailer for profit. A 2' x 4' or 3' x 5' deck would be pretty easy to build, and adding two 20" wheels from a BMX bike would be easy enough. I haven't given much thought to pricing, but it would not exactly be cheap. Think more than $500, but not more than $1,000, depending on what you want and how much of the material you can scrounge up yourself. You can build most of it from an old steel bed frame; surely someone has one in their attic that they can give up for the good of the cause. 8) Here is a 3' x 5' bike carrier I recently built; just imagine this with 2 wheels and a wooden or diamond plate aluminum deck.

Was never thinking of seatpost as the primary load bearing element, the design I have in mind would put the majority of the stresses on the eyelets near the rear axle. More just to provide a little more up/down stability than anything. Thoughts about braking system on the bike appreciated. The photo reminds me... one of the thoughts started with a car cargo hitch carrier as the basis for the main frame. Good is the accessorization for cargo is certainly easy, and it's sturdy not too expensive. But getting the wheels and trailer arm figured out on something already powder coated, and the arm that goes in the hitch itself... dunno. Anyways, much silliness, but it's fun to kick around.

Not sure how successful this was (looks like they are "redesigning" and don't actually have a product right now), but it is not a completely alien idea: http://www.ridekick.com/

OK, so here's the latest in the thought process. I'm giving up on (this) winter. Just not happening in time. In the spring, when the weather requires less convincing and my oldest is a touch taller, I'm going to see if she's big enough to be a stoker on a tandem (she's 4'3" now, guessing 4'4" or 4'5" in spring... is that tall enough (barely) for a regular tandem, or still in "childback" only mode?), and once my two younger ones are big enough that I can't do the trailer anymore (which may also be spring, we'll see), I plunk down the cash for a weehoo igo two (two little ones ride low, front to back, single rear freewheel that the front of the two can crank against). Downsides: Long front to back considering it's not esp cargo friendly No occupant protection from elements (except optional for rear-most occupant) Not real cheap (the trailer itself is money, but in total it's not worse than most of the other options, depending on the tandem of course). Upsides: (Almost) everyone works/has fun cranking. Reasonably low center of gravity Very adaptable (can remove one of the two seats and accomodate a bigger kid in back when my oldest has more experience as a road rider, freeing a seat on the tandem), and can easily attach/detach trailer to single bike if oldest is "doing her own thing" that evening. Actually based on products that might work from the get-go and be easier to maintain. The cargo thing will probably be limited to panniers and the current double trailer for the foreseeable future. Giant eagle yes, Costco no.

I'm glad you're doing something that sounds more reasonable.

Have you thought about buying a flatbed utility trailer? http://www.bikesatwork.com/store/product/64a-bicycle-trailer You could bolt on a few child seats (with seatbelts) of the appropriate size/type for the kids and even change them out as they get older. The trailer is designed to haul 300lbs and it's center of gravity is probably lower than the weehoo and should be more stable. You would then have a useful trailer after the kids are grown up and on their own bikes - the weehoo not so much.

The utility trailer part of my idea was never the lynchpin... those are out there as real products and even not too forbidding looking DIY. But a tad expensive in the former case, and the DIY for that has the same problem as the surge braking... I probably can't jump on solo with no expertise and no tools and expect that I'll find a way to get it done. Speaking of the surge brake, that's basically the thing I feel is necessary to make this safe enough for family transport. And it's basically unavailable in a bike scale product (totally unavailable in at the slightly larger scale that would meet my needs) so you're forced to diy. It doesn't necessarily look that hard. and frankly I'm a little peeved, but I have no realistic hope of getting it done without someone who knows what they're doing donating equipment, expertise, and time. Anyways, as proposed, tandem + weehoo, if the oldest/heaviest isn't in a trailer but on the bike, I have at least somewhat less in the way of fishtailing concerns. Not that we'll be approaching any turns aggressively but somewhat less concerned a mellow ride would be likely to suddenly very scary. I like the fact that the weehoo is a single wheel trailer and built with at least a little nimbleness as a priority, and I like the idea that my oldest would have to pedal and the middle one would at least have the option. Also like that both the youngest two could plausibly sack out on a longer ride... this setup seems as bike touring friendly (as long as the includes motels) as any other. I expect the weehoo would have a second life after the oldest had migrated off the tandem. Middle child could move to the tandem when she's ready and the youngest could take her spot, at first leaving the rear seat as a second class but fudgeble cargo area (tarps and bungees can do anything), and then eventually as she gets bigger the front seat could be taken out to accommodate her longer legs. The tandem could also be dual purpose if my oldest can ride on a full-size one come spring and we're not stuck on a child-back model.

I've followed this off and on and am wondering why you feel you need a surge brake. I have a triple (3-seater) that I've used to tow a 2-child trailer, so was riding with myself, my wife, and my 3 kids, for a total weight of over 500 lbs. and the V-brakes plus drum brake were more than enough to keep our speed in check. We have ridden this setup around town and also on some longer rides and have never had a braking problem. For 3 kids, as long as you aren't doing super long descents normal brakes should be sufficient. I think I showed ours to you last year, but I would suggest you keep a look out for a used Bike Friday Family Triple or Triple XL. I bit whippy, but works fine and super adjustable. The XL is supposed to be stiffer and a better ride than the Family Triple. PM me if you'd like to take it out for a test drive.

Test drive opportunity appreciated. Will PM you and also Eric about the Madsen, try and arrange test rides to get a feel or things. Those long tandems are crazy expensive that I've seen is my concern (unless you're looking to part with something ;)). Presumably because it's a niche item so few builders, and shipping a long tandem frame is an ordeal. This seemed kind of brilliant (if it's sturdy enough) http://www.pedouins.org/quint-5-4-3-2.html but doesn't look like it's being sold as a product necessarily. Will update if I hear back from them. Surge break obsession is owing to fishtailing concerns from having momentum that's not directly braked going to the outside of corners. But it's significantly less of a concern if the oldest takes her momentum from the trailer and instead adds her weight in front of and on top of, the rear bicycle tire. The weehoo is a good concept. I'm not at all confident, mind you, that the middle daughter would be big enough to be on a tandem normally before she and her younger sister combined would be pushing the limits of the igo 2 (wish that thing were longer and rated for 130 pounds, not 100). So we may have an awkard transition year where we need to chain a crank up to her level or just install footrests but I think that makes more sense than having a childback tandem that tops out at a an age/size short of what I need for my oldest before she's more ready to handle these hills and traffic.

@byogman: In my experience hauling kids-n-cargo, fishtailing or jackknifing isn't really an issue until you have two flex points in the mix, e.g. bike->trail-a-bike->trailer. One flex point seems to result in perfectly fine handling, including sudden braking at some speed (15 mph-ish) downhill. However, I haven't tested that hypothesis with power being applied from the rear while braking from the front, such as pedaling from the wego (or power from a hypothetical assist trailer) whilst the tandem is braking. *Maybe* that could lead to fishtailing?

@reddan, well, if you're careful going downhill I think you're right. Downhill, it's easy to get going too fast and lose control around a turn.

People with kids: I just found out my niece is too big for the cargo trailer now. (7 going on, 8) Does anybody have experience riding with kids that age? I think the tag-alongs were discouraged earlier in this thread. What's the alternative? The MADSEN looks cool, but $1875 is a steep price and I think the thing probably weighs as much as my sister who would be using it and she lives on a second floor apartment

I'm discovering the 8-12 ages are hard to deal with. I still cargo bike both mine around (8 and 10), but that is getting harder and harder. And they are still too small to get anywhere quickly riding separate bikes, not to mention having to deal with 3 bikes, vs a single cargo bike. If we are talking about one kid, a 24" wheeled trail-a-bike would be a good option, the 20" ones get too small around age 8.

@Pierce: you can probably find an inexpensive tandem to accommodate a kid of that age. That's the route I went when my son(now almost 10) got a bit big for the trail-a-bike. Now I have the annoying wait until his legs are long enough that I can attach the trail-a-bike to his seatpost, so his sister(almost 6) can pedal too.

Tandem bakfeits

Getting a tandem or cargobike into a 2nd floor apartment with no elevator is going to be a mess.

The age range, say 7-11,8-12 years are a difficult problem, to an extent speed but mainly the appropriateness to the environment. And what's messed up there is the environment. BIG TIME. Kids at that age WANT to be riding. The idea that my oldest can't just go, safely is what makes ALL of this so damn complicated. It's so stupid. I don't have the problem with stairs, however I do have a very steep driveway. So, that similarly brings weight into question and also brings different questions into play... low speed stability how much speed any of these solutions can/should take coming into the very sharp transition from sidewalk to the initial 25-30% gradient. Also, every little bit of extra power helps. Reddan, where (other than wally world) do you find a tandem that's inexpensive?

@byogman They pop up on Craigslist pretty often. I bet there might be a few in the basement of Thick too. Since I only have one kid to contend with, I'll have to check out FreeRide and see if they have any 24" tag alongs.

@byogman: I got mine at Thick...a nice fantastic deal on a dust-covered Fuji that had been hanging from the ceiling for a few years. Ambridge Bike Shop used to carry a lot of tandems, IIRC. I don't know what their current inventory looks like, though.

Maybe a topic for another thread, but at what age did any of you start riding solo? My parents did not ride bikes, but with 4 kids, 1 car, and dad took it to work, I suspect I started riding around on my own when I was somewhere in the 8 to 10 year old range. Certainly before I could get on a bike with large wheels. It was a quiet area traffic wise with wide streets though.

I started riding around the neighborhood when I was pretty young. I recall rollerblading to school in 5th grade. Rode a bike to school a couple of times in 8th grade. Then started riding regularly to school either freshman summer school or tenth grade. But I pretty much only rode to school and work, neither of which was particularly hairy.

I got a 5 speed Schwinn Stingray when I was 10 and that was my transportation everywhere in my small town, public pool, library, woods, dirt lots, no parental supervision.

...also, no helmets. The only helmets were the kind racers wore, leather straps to hold everything together so cleanup was easier after a crash. I remember getting my sister's hand-me-down bike when I was too young for school. I loved that red bike. But I think I wasn't allowed to ride outside of the alley behind my house, at the time.

I was riding on the road at age 6. I was taking unsupervised 8-mile-each-way trips on Saturday mornings by 10. High school, unicycled four miles to school because it was faster than the school bus. My father was a road-riding motorcyclist long before it was cool, so I was merely following his lead.

Any non-intuitive tips to teaching a kid how to ride a bike? Going to try and teach my niece tomorrow