A Minor Hitch......

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#1
..... or at least a lighter hitch :D

The very strong, and very heavy rack I build for the back of my Mixer 8 to tow my trailer has worked well, really, it has been a good performer, but, man it makes the bike heavy :( I could live with that, but I'm finding that having the hitching point over the center of the back wheel is not so good, if I turn and the trailer is loaded, it kind of makes the bike want to stand up, instead of lean into a corner, if I hit the brakes in a corner, it is even worse. Before with the Cannondale I had the hitch point much closer to the seat post, and I did not feel this "Push" like I do now.

I'll ditch the rear rack and shave off a bunch of weight.

My plan is to make a hitch that clamps onto the seatpost and the seat tube.

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver2_two_clamps_a.jpg&hash=4e9674fd1bbc8c91f2631a465ba698ec


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver2_two_clamps_b.jpg&hash=958c57d94fd533a32a5690998aa80e13

Here you can see the two clamps that I made, they fit rather well, the clamps sill need a bit of cleaning up, but there is welding etc to do yet, so I'll not bother until later.

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver2_1st_mock-up.jpg&hash=a27eb400af34ba8b84ceb92ca0a658ec

That is the basic mock-up I have rattling around inside my brain right now :rolleyes:

I'll gusset the joints so that they are stronger and make very sure that the pieces fit together well before I weld them, I want to make sure that this is light, but strong.

So, what do you guys think?

The top piece, the horizontal one will be made from 21mm square tubing the piece that goes from the lower clamp will be made from 16mm square tubing.

The inside of the clamps have been sanded smooth, so they fit very well, I don't plan on putting anything between the clamps and the seat tube or seat post, except a thin coat of paint to stop rust.

The way I see it,force is applied to the hitch and through it the bicycle in three directions;
1) front to back
2) up and down
3) side to side

I think with the two clamps spaced as they are the up and down and the back to back forces should not be a worry, the only thing I see that could be a potential problem is the side to side, specifically a push to the side. Pulling should not present much side to side stress, as it should straighten out as it pulls, but stopping might present some side to side moment. I think the clamps on the tubes should resist that side to side moment, but I guess I'll find out:eek: Maybe I could put spacer on the side of the lower tube of the hitch where it passes through the seat stays, so it could not twist the hitch...?

I always get such great feedback and ideas here I really do want your thoughts and suggestions.
 

GSAstuto

Maximum Pace
Oct 11, 2009
945
242
103
tokyo
www.roadfixie.com
#3
I hope that seat tube is not double butted ... By the way, my daughter's '3rd wheel' bike uses a nice seatpost clamp with ball joint. Why don't you just order something like that and splice it in? You are gettiing very close to that concept anyway.

http://www.trail-a-bike.com/products/parts/

And not certain why you need the lower mount unless you are trying to lower the torque angle?? from an engineering perspective your effective torque vector will be roughly halfway between the 2 points. Is that really a tangible difference than just the upper point?

I can see the advantage of getting the tongue weight more under , or slightly forward of your center of mass, and as low as possible on the seattube to reduce the torque steering effects. Perhaps you could use this as a test bed to find the optimum mounting location. I guess my concern (echoing my above statement) , is that if you have DB tubing you are skating on the thinest part of the pond. So, alternativly - you may look at a much broader clamping surface and / or making sure you have an extra long seatpost fitted so that the lower clamp is surrounding not only seattube, but also the seatpost extension.

Lastly - I think you could make these parts out of alloy (6061) with no structual issues.
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#5
I hope that seat tube is not double butted ... By the way, my daughter's '3rd wheel' bike uses a nice seatpost clamp with ball joint. Why don't you just order something like that and splice it in? You are gettiing very close to that concept anyway.

http://www.trail-a-bike.com/products/parts/

And not certain why you need the lower mount unless you are trying to lower the torque angle?? from an engineering perspective your effective torque vector will be roughly halfway between the 2 points. Is that really a tangible difference than just the upper point?

I can see the advantage of getting the tongue weight more under , or slightly forward of your center of mass, and as low as possible on the seattube to reduce the torque steering effects. Perhaps you could use this as a test bed to find the optimum mounting location. I guess my concern (echoing my above statement) , is that if you have DB tubing you are skating on the thinest part of the pond. So, alternativly - you may look at a much broader clamping surface and / or making sure you have an extra long seatpost fitted so that the lower clamp is surrounding not only seattube, but also the seatpost extension.

Lastly - I think you could make these parts out of alloy (6061) with no structual issues.
Tim, I do think that getting the tongue weight more under me will greatly improve handling, but I too worry about the tube and that this could wreak the frame.
The frame is Tange Prestige Double Butted tubing.

The longer seat post is a good idea, as well as a broader clamping surface.

I'd love to make it out of 6061 but my aluminum welding set up sucks, so steel is the way to go!

Still mashing ideas around, so keep them coming! :D
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#6
OK, I had some time this morning, and I did some more mocking up.

Some pics....

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_1.jpg&hash=3079feec8bfdd50f2c76f9ffb3f50a1d


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_2.jpg&hash=c9f443a2ac282a6c0c86fc19a0f0fd4f


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_3.jpg&hash=704e45384664c678787dc632f1794159


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_4.jpg&hash=1ea4116e3d2f48af0acc2c3f586471c1


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_5.jpg&hash=c3dd5b1435ec657602926a082d94eee9


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_6.jpg&hash=6ea7bb6abbcec345e97f3074b582de64


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_7.jpg&hash=1928ac4a9dfbc426f44d9fcd434b9745


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_9.jpg&hash=c93744149609a7aabdf8538f2cd43b00

Just to show that the clamps fit very well on the tubes

Compared to the first mock up, in this one I moved the bottom clamp up the seat post a lot higher. I did this to get the clamp on the part of the tubing that is not butted, as in the thicker part of the tubing. With the seatpost out I could look down into the tube and you can see where the grease from the seatpost is not smooth, this is the area, I assume that the butting starts as the tube inside diameter increases and the seat post no longer touches the inside of the tube.

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fhitch_ver3_10.jpg&hash=57a514aff6d2a546cfade6d30b60eeaf


If you look at the above pic, I've marked a few things out.

In red is the height of the trailer's tongue, I want the hitch slightly below this height so I can adjust it upwards to get the trailer level with washers. In the picture it looks well below that level, but is is not, that is just the camera angle.

In green is where the internal tube butting starts. I put the clamp above this level by a bit, just to be safe.

In Yellow is where the seat post ends. I was surprised at how long the seat post is, but there you go.

I think that by doubling the thickness of the clamps, and by using this design, it should work very well, be compact and out of the way and a LOT lighter than what I have on there now.

Comments, suggestions, questions etc all welcome!

Cheers!
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#7
I doubled up the size of the clamps......

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Fnew_clamps.jpg&hash=afa6a9f12c112a23a036440037490c7d


They are quite a bit thicker now and heavier :rolleyes: But they should do the job.

Tomorrow Sunday I have some stuff on the "Honey to do" list that I have to get round to, but I hope to get most of my afternoon in working on the hitch, I think I can get it done, as there is not that much to do really, this is a very simple hitch compared to the rack I built before.

Wish me luck!
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#8
I got it done today!

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_2.jpg&hash=e5d46b752d00196c29cd44f3efdecb86


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_1.jpg&hash=566d4ceb31629972789767f506e3f2b1


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_3.jpg&hash=6ee52bfcda3b230126cfb1993e1aa0e2


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_4.jpg&hash=12cfc59308d07c85293ffd57fcb7bd95


Still needs some touching up and some paint, but it is good and solid, I'll know better how it works on the next heavy load.

For riding around the trailer feels much better, seems to feel like it follows the bike better and does not have the tenancy to push the bike sideways when I turn, even very sharply.

The old massive rack/hitch weighed almost exactly 4 kg, the new set up is 1.25 Kg.

Time will tell I guess!
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#9
I know you are all out there enjoying the fine weather and getting in epic rides, but I'm still working away delivering beer :D

proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_5.jpg&hash=085481145c8ce08e7e52374445456df8


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_6.jpg&hash=cf356988830494c32340a1a21da9d129


proxy.php?image=http%3A%2F%2Fi295.photobucket.com%2Falbums%2Fmm155%2FStuInTokyo%2Fcycling%2FTrailer_Hitch_ver_2%2Ftrailer_hitch_ver_2_7.jpg&hash=de322466a415dbdc7a3cbd1dc8a1392c

That is how it all looks in use, I know it still needs sanding and some painting, but I'm going to try it out like this for a while. I might buy a light weight aluminum rack for it, or I might not, haven't decided yet.

Today I had a medium heavy load of about 70Kg including the trailer and I have to say the new hitch preformed very well indeed! When I turn, I do not feel that the trailer is pushing the bike over sideways. The biggest difference is when I get out of the saddle and kick, before the bike would want to stay leaned over, it was hard to kick moving the bike side to side, using your upper body, not very good at all, and felt very unstable. Now I can get up and kick, moving the bike side to side with little problem at all. When I turn in a tight circle it feels much better, the trailer is not trying to push the bike over all the time.

I guess time will tell it this works or not, I'm optimistic that this will work out. The only fear I have is that the bottom clamp will somehow comprimise the seat tube, but, the clamping surface is large, and the seat post goes well past the point where the clamp is attached, so the seat post is acting as kind of a back up for the seat tube....... I hope......

I guess we shall see, but so far, so good!
 

jdd

Maximum Pace
Hardest Crash
Jul 26, 2008
2,497
628
133
Kanazawa
#10
Maybe I've been too long out of Tokyo, but do you really need the lock there on the hitch?

Is it the bike you're protecting by locking it to the trailer, or, heaven forbid, is it the trailer that you think someone might sneak off with?

John D.
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#11
Maybe I've been too long out of Tokyo, but do you really need the lock there on the hitch?

Is it the bike you're protecting by locking it to the trailer, or, heaven forbid, is it the trailer that you think someone might sneak off with?

John D.
All of the above! :rolleyes: :D

The bike locked to the trailer keeps the bike from being easily stolen, the trailer has a Mamachari lock thing on it.

The thing is the lock acts as the pin that holds the trailer to the hitch.

If you look at this video......

http://www.youtube.com/watch?v=178znt79aW8

..... you will see how my hitch works, this is where I got the idea from :D
 
Dec 4, 2008
169
3
38
Tokyo
#17
Very impressive!

Do I want a trailer? I have decided that I can carry various bits of camera paraphernalia on board. The weight is not so much the issue, more the strange shapes ie stands and supports maybe 5' long. Perhaps an all-up load of 25kg.

I had visions of a heavy-duty rack, equipped with vertical-mount stand holders either side, and the main load on the rack, but the c.o.g aspect is worrying. Perhaps splitting the main load between 2 panniers, and the stands (which weigh relatively little on their own) sprouting up from the rack. And perhaps able to support a pennant;)

Your trailer has no issues with c.o.g I assume ( unless cornering hard?)
 
Sep 2, 2009
5
0
0
#18
Good stuff!

Always a big fan of a nice build.

Have you contacted Charge about this, to see what they have to say about the stresses this is putting on the frame / post?
 

StuInTokyo

Maximum Pace
Dec 3, 2010
1,662
62
78
#19
Very impressive!

Do I want a trailer? I have decided that I can carry various bits of camera paraphernalia on board. The weight is not so much the issue, more the strange shapes ie stands and supports maybe 5' long. Perhaps an all-up load of 25kg.

I had visions of a heavy-duty rack, equipped with vertical-mount stand holders either side, and the main load on the rack, but the c.o.g aspect is worrying. Perhaps splitting the main load between 2 panniers, and the stands (which weigh relatively little on their own) sprouting up from the rack. And perhaps able to support a pennant;)

Your trailer has no issues with c.o.g I assume ( unless cornering hard?)
Thanks!

If you do go the trailer route, I think you would only need a single wheel trailer, these are much better for the kind of load you are looking at and they really work well for that kind of thing.