#11
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Trailer hitches
In article ,
Frank Krygowski wrote: On Monday, March 3, 2014 12:02:31 AM UTC-5, Ralph Barone wrote: Any comments or insight into which of these methods would work best for a fairly heavy duty application? I think #3 is out for physics reasons and #4 is out for construction reasons. I suspect #1 is the easiest to build, but that #2 might be a little stronger. Then again, #2 might exert more torque on the bike frame. If you have real world experience you can share, that might be even better. Thanks. I have (significant) experience only with the left side rear axle hitch scheme, your #1. It seems to have become the most common for two wheel trailers. I haven't used any 200 pound, self-powered trailer, but I've ridden a few hundred miles with luggage towed behind a Bike Friday. I've had no significant problems. Neither has my good friend who used that scheme to haul his large dog for many, many hundreds of miles. Well, that's one good data point. I'm thinking of this as a way to introduce my wife to bike touring, so I don't want to be wrestling with the bike for hours on end. I recall when my daughter was still on her Trail-a-bike, I would come back from rides with sore arms from counteracting the torque from my daughter rocking back and forth on the seat. I don't think you'll have a problem due to the asymmetry of the hitch. Yes, in the top view, you'll see a counterclockwise torque when the trailer is being towed, and a clockwise one when the powered trailer is pushing the bike. But the moment arm is small, and the necessary resisting lateral force from the front tire should be very small. I certainly never noticed any instability when braking my bike+trailer on a steep downhill, and that situation is similar to your "powered trailer" mode. Asymmetry doesn't bother me a lot on #1 because you may as well offset the tongue anyway so the force is applied inline with the center line of the bike. My concerns with #1 are more that stresses are being applied to only one chainstay. I suppose if the rear QR is tight enough, some of the force should get transferred through the axle to the right-hand chainstay. Further thoughts on scheme #3, the seatpost mount: It requires a lot more metal for the tongue, and for the weights you're describing, might give an opportunity for some serious flexing. It will be a bigger trailer overall, perhaps complicating storing and transporting. There's a modified version of your #2 that's been used, essentially a stretched tetrahedron supporting a hitch point just behind the bottom of the rear fender. Picture an extra pair of stays, roughly parallel to the chainstays and extending from the rear dropouts to a dummy rear axle behind the fender. Now run a pair of stays from the seatpost or seat cluster down to that dummy rear axle, to keep it at the proper height. That's sketched in the "Cycling with Love" chapter of _Effective Cycling_, towing a kid's bike. With your trailer, the hitch could be a ball & socket. But I don't see any great advantage over the left-side axle hitch. I've got a design sketched up that uses an MTB front fork clamped into the rear QR, plus some aircraft cable going up over the seatpost to build your stretched tetrahedron. As long as the hitch point doesn't flip upwards, it should be stable. I've got a couple other books with trailer designs that I could describe. But I think you're well beyond due diligence in examining prior art. By this stage, the crusty old guy who taught me machine shop techniques would be yelling "Just do it!" (That was way before Nike said that, BTW. He should have copyrighted it.) I tend to be of the "Measure twice, cut once, f#$k it up anyway" school, so I try to design things a little more thoroughly before I start building. - Frank Krygowski |
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#12
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Trailer hitches
In article ,
James wrote: On 03/03/14 16:02, Ralph Barone wrote: I'm (still) working on the design for a "recumbent trailer trike", essentially a delta trike with no front wheel, but a hitch which will connect to my diamond frame bike. I've got a lot of the details worked out, but I'm still agonizing over the hitch design. The trailer will have brakes and a drive train, so it will be capable of both pushing and pulling, and by the time we add the weight of the trailer, rider and storage (this is for touring), we might be nearing 200 lbs being pulled by the hitch (tongue load should be substantially lower if I get the seat location right). As I see it, there are 4 options in terms of hitch location. 1) Asymmetrical rear axle mount. Like most of the Burley trailers. A small hitch is attached to the left side of the axle and the trailer mounts there. The advantage is that forces are applied low and somewhat forwards on the frame. The disadvantages are that force is only applied to one chainstay, and the trailer hitch has to have a substantial bend in it to prevent striking the rear tire during right hand turns. 2) Symmetrical rear axle mount. Like the Bob Yak. A subframe mounts to both sides of the rear axle and the trailer mounts to the subframe at a point in line with the center of the bike, but behind the rear tire. The advantage is that the force is applied equally to both chainstays. The disadvantage is that sideways force is applied behind the rear wheel, which gives more torque on the frame. You also have to worry about holding up the hitch point if the trailer needs to stay upright when the front bike leans (which the Yak doesn't need to do). 3) Seatpost mount. Like most trail-a-bikes. A clamp goes onto the seat tube. The seat tube should be fairly strong and is in line with the center of the bike, but the attachment point is too high and excessive force applied during braking could push the rear end off the ground. 4) Bottom bracket mount. Only ever seen on the defunct Chariot Sidecarrier. From a pure physics point of view, this might be the best, as external forces are applied quite low and in the center of the frame. Unfortunately, the practical aspects of trying to connect that hitch to a trailer are pure hell and it really only works when the trailer is beside the bike (as in the Sidecarrier). Any comments or insight into which of these methods would work best for a fairly heavy duty application? I think #3 is out for physics reasons and #4 is out for construction reasons. I suspect #1 is the easiest to build, but that #2 might be a little stronger. Then again, #2 might exert more torque on the bike frame. If you have real world experience you can share, that might be even better. Thanks. I have no real world experience, only gut feel after some thought. I would like to build a single wheel trailer, like a Bob design. My gut feel tells me this is the best approach. I have yet to construct or test anything though. I think a slightly longer draw bar might be beneficial, to put more weight over the trailer wheel and less on the tow point. Interested in how you go. If you want more weight on the wheel without a long draw bar, consider something like this http://www.extrawheel.com/ |
#14
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Trailer hitches
On Monday, March 3, 2014 10:24:54 PM UTC-5, Ralph Barone wrote:
I'm thinking of this as a way to introduce my wife to bike touring... Maybe you've already explained this, but: Is there a reason you don't just use a tandem? - Frank Krygowski |
#15
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Trailer hitches
Frank Krygowski wrote:
On Monday, March 3, 2014 10:24:54 PM UTC-5, Ralph Barone wrote: I'm thinking of this as a way to introduce my wife to bike touring... Maybe you've already explained this, but: Is there a reason you don't just use a tandem? - Frank Krygowski Pigheadedness, mostly. Plus, I think she would be more comfortable on a bent (and I'm not ready to shell out the cash for a Hase Pino). |
#16
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Trailer hitches
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#17
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Trailer hitches
On Mon, 03 Mar 2014 19:24:54 -0800, Ralph Barone
wrote: In article , Frank Krygowski wrote: On Monday, March 3, 2014 12:02:31 AM UTC-5, Ralph Barone wrote: Any comments or insight into which of these methods would work best for a fairly heavy duty application? I think #3 is out for physics reasons and #4 is out for construction reasons. I suspect #1 is the easiest to build, but that #2 might be a little stronger. Then again, #2 might exert more torque on the bike frame. If you have real world experience you can share, that might be even better. Thanks. I have (significant) experience only with the left side rear axle hitch scheme, your #1. It seems to have become the most common for two wheel trailers. I haven't used any 200 pound, self-powered trailer, but I've ridden a few hundred miles with luggage towed behind a Bike Friday. I've had no significant problems. Neither has my good friend who used that scheme to haul his large dog for many, many hundreds of miles. Well, that's one good data point. I'm thinking of this as a way to introduce my wife to bike touring, so I don't want to be wrestling with the bike for hours on end. I recall when my daughter was still on her Trail-a-bike, I would come back from rides with sore arms from counteracting the torque from my daughter rocking back and forth on the seat. I don't think you'll have a problem due to the asymmetry of the hitch. Yes, in the top view, you'll see a counterclockwise torque when the trailer is being towed, and a clockwise one when the powered trailer is pushing the bike. But the moment arm is small, and the necessary resisting lateral force from the front tire should be very small. I certainly never noticed any instability when braking my bike+trailer on a steep downhill, and that situation is similar to your "powered trailer" mode. Asymmetry doesn't bother me a lot on #1 because you may as well offset the tongue anyway so the force is applied inline with the center line of the bike. My concerns with #1 are more that stresses are being applied to only one chainstay. I suppose if the rear QR is tight enough, some of the force should get transferred through the axle to the right-hand chainstay. Further thoughts on scheme #3, the seatpost mount: It requires a lot more metal for the tongue, and for the weights you're describing, might give an opportunity for some serious flexing. It will be a bigger trailer overall, perhaps complicating storing and transporting. There's a modified version of your #2 that's been used, essentially a stretched tetrahedron supporting a hitch point just behind the bottom of the rear fender. Picture an extra pair of stays, roughly parallel to the chainstays and extending from the rear dropouts to a dummy rear axle behind the fender. Now run a pair of stays from the seatpost or seat cluster down to that dummy rear axle, to keep it at the proper height. That's sketched in the "Cycling with Love" chapter of _Effective Cycling_, towing a kid's bike. With your trailer, the hitch could be a ball & socket. But I don't see any great advantage over the left-side axle hitch. I've got a design sketched up that uses an MTB front fork clamped into the rear QR, plus some aircraft cable going up over the seatpost to build your stretched tetrahedron. As long as the hitch point doesn't flip upwards, it should be stable. I've got a couple other books with trailer designs that I could describe. But I think you're well beyond due diligence in examining prior art. By this stage, the crusty old guy who taught me machine shop techniques would be yelling "Just do it!" (That was way before Nike said that, BTW. He should have copyrighted it.) I tend to be of the "Measure twice, cut once, f#$k it up anyway" school, so I try to design things a little more thoroughly before I start building. - Frank Krygowski I made a hitch using quick-connect air connector. The male end is on a "universal joint" at the rear axle and the socket is on the trailer hitch. I pull a converted Burley kid hauler with an aluminum box and 3 12 volt batteries behind my e-bike for long range. |
#18
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Trailer hitches
I made a hitch using quick-connect air connector. The male end is on
a "universal joint" at the rear axle and the socket is on the trailer hitch. I pull a converted Burley kid hauler with an aluminum box and 3 12 volt batteries behind my e-bike for long range.~~~~~~~~~~~~~~~~~ photo ? |
#19
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Trailer hitches
wrote:
On Mon, 03 Mar 2014 19:24:54 -0800, Ralph Barone wrote: In article , Frank Krygowski wrote: On Monday, March 3, 2014 12:02:31 AM UTC-5, Ralph Barone wrote: Any comments or insight into which of these methods would work best for a fairly heavy duty application? I think #3 is out for physics reasons and #4 is out for construction reasons. I suspect #1 is the easiest to build, but that #2 might be a little stronger. Then again, #2 might exert more torque on the bike frame. If you have real world experience you can share, that might be even better. Thanks. I have (significant) experience only with the left side rear axle hitch scheme, your #1. It seems to have become the most common for two wheel trailers. I haven't used any 200 pound, self-powered trailer, but I've ridden a few hundred miles with luggage towed behind a Bike Friday. I've had no significant problems. Neither has my good friend who used that scheme to haul his large dog for many, many hundreds of miles. Well, that's one good data point. I'm thinking of this as a way to introduce my wife to bike touring, so I don't want to be wrestling with the bike for hours on end. I recall when my daughter was still on her Trail-a-bike, I would come back from rides with sore arms from counteracting the torque from my daughter rocking back and forth on the seat. I don't think you'll have a problem due to the asymmetry of the hitch. Yes, in the top view, you'll see a counterclockwise torque when the trailer is being towed, and a clockwise one when the powered trailer is pushing the bike. But the moment arm is small, and the necessary resisting lateral force from the front tire should be very small. I certainly never noticed any instability when braking my bike+trailer on a steep downhill, and that situation is similar to your "powered trailer" mode. Asymmetry doesn't bother me a lot on #1 because you may as well offset the tongue anyway so the force is applied inline with the center line of the bike. My concerns with #1 are more that stresses are being applied to only one chainstay. I suppose if the rear QR is tight enough, some of the force should get transferred through the axle to the right-hand chainstay. Further thoughts on scheme #3, the seatpost mount: It requires a lot more metal for the tongue, and for the weights you're describing, might give an opportunity for some serious flexing. It will be a bigger trailer overall, perhaps complicating storing and transporting. There's a modified version of your #2 that's been used, essentially a stretched tetrahedron supporting a hitch point just behind the bottom of the rear fender. Picture an extra pair of stays, roughly parallel to the chainstays and extending from the rear dropouts to a dummy rear axle behind the fender. Now run a pair of stays from the seatpost or seat cluster down to that dummy rear axle, to keep it at the proper height. That's sketched in the "Cycling with Love" chapter of _Effective Cycling_, towing a kid's bike. With your trailer, the hitch could be a ball & socket. But I don't see any great advantage over the left-side axle hitch. I've got a design sketched up that uses an MTB front fork clamped into the rear QR, plus some aircraft cable going up over the seatpost to build your stretched tetrahedron. As long as the hitch point doesn't flip upwards, it should be stable. I've got a couple other books with trailer designs that I could describe. But I think you're well beyond due diligence in examining prior art. By this stage, the crusty old guy who taught me machine shop techniques would be yelling "Just do it!" (That was way before Nike said that, BTW. He should have copyrighted it.) I tend to be of the "Measure twice, cut once, f#$k it up anyway" school, so I try to design things a little more thoroughly before I start building. - Frank Krygowski I made a hitch using quick-connect air connector. The male end is on a "universal joint" at the rear axle and the socket is on the trailer hitch. I pull a converted Burley kid hauler with an aluminum box and 3 12 volt batteries behind my e-bike for long range. I've avoided considering those connectors because I wasn't sure that I could find any engineering data for pullout strength. I'd be willing to accept losing a trailer full of luggage, but not one holding my wife. |
#20
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Trailer hitches
wrote:
Mrs Barone ride this ? http://i211.photobucket.com/albums/b...DBRONCOvs3.jpg Too much macho. Not enough comfy. :-) |
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