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Lightweight sidecar for 125cc bike
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c64club
Posted 7/6/2011 6:20 AM (#58871)
Subject: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
My bike is Romet K125, it's a Honda CG125 frame and engine exact copy with details like tank, seat etc. from Suzuki gs125. Kind of chinese "license megamix". It has also muuuuch better brakes than original Honda and produces 10HP.

I have "tested" it with 80lb 2-wheeled trailer with Sputnik sidecar (another 200lb) on the trailer and Romet pulled such rig properly, 300 miles from Sputnik's previous owner to my home. To be precise - properly for me, which means 35MPH with some RPM reserve and without torturing the engine.
But few frame mods later, when I added subframe and attached Sputnik as a sidecar (veeery temporary construction ) it wasn't comfortable because sidecar's weight and there were no possibility to carry anything in sidecar. Unmounting Sputnik's body gave 85lb sidecar and it's acceptable weight, I could carry about 60-70lb load. Sputnik went to other guy who has Intruder 1400.

I decided to build my own sidecar with goal to not exceed 85 lb. And it should have a drum brake launched together with rear brake. Such construction would also benefit with smaller size than Sputnik and it will better fit my bike's size. There are many such constructions in Asia, they even act as taxi, so I think it's really possible to make.
My first thoughts are:
-"copy" of some bigger sidecar's frame but 70% in size
-16" alluminuim alloy wheel (there are few ones in my local junkyard)
-body made of thin plywood or 2mm fiberglass-compound boards, I have few square meters of it laying around

Some dude gave me an idea to make "semi flex" sidecar with rigid axle but with struts replaced by rear dmapers from some small motorcycle - some between flex and suspended classic. But I think it couldn't be comfortable for dog.

Do you have any suggestions for building such lightweight sidecar? Thinner-wall pipes, some lightweight patent for suspension?


Before You ask me to change my bike to some 500cc or so :D :
-I like it, especially due its great MPG (85 with heavy trailer/load to 105 solo)
-it's silent, cheap, has simple construction, is equipped with kickstarter and generally looks like motorbike, not like 2-wheeled USS Enterprise
-I don't drive above 45 MPH, typically about 35-40 solo
-I can afford to use it with my $600/month salary and gas prices around $7 per gallon

Edited by c64club 7/13/2011 6:56 AM
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SwampFox
Posted 7/6/2011 7:20 AM (#58873 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 1312
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Location: Summer Grove, LA USA
Maybe you can pattern after the Enduro sidecars common to the Northwest USA region, such as found here:

http://www.dmcsidecars.com/Sidecars/dualsportsidecars.htm

Sorry, I'm do not have sufficient technical knowledge to advise as to materials and assembly.
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c64club
Posted 7/6/2011 7:39 AM (#58874 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Is this suspended?
Looks gerat, simple, lightweight and should be simple to add dog-wagon(kennel?) body.
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SwampFox
Posted 7/6/2011 7:59 AM (#58875 - in reply to #58874)
Subject: Re: Lightweight sidecar for 125cc bike



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Location: Summer Grove, LA USA
c64club - 7/6/2011 7:39 AM

Is this suspended?
Looks great, simple, lightweight and should be simple to add dog-wagon(kennel?) body.


I've seen a photo with a fellow traveling with his dog in a kennel on a similar sidecar with the seat removed.

I defer the Lonnie, Jay and others as to the technical aspects.
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c64club
Posted 7/6/2011 8:05 AM (#58876 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Thanks.

Even if this isn't suspended, I can always mount the kennel on some soft/springing/suspending "patents"

Edited by c64club 7/6/2011 8:06 AM
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Hack'n
Posted 7/6/2011 1:01 PM (#58880 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Location: Boise, Idaho
Here's a torsional suspension leading link chassis that is fairly easy to fabricate with .120" wall square tubing. It uses a 1" timken bearing axle that supports a disc brake if desired.

Lonnie



(Dual Sport sidecar 008 (Large).jpg)



Attachments
----------------
Attachments Dual Sport sidecar 008 (Large).jpg (92KB - 9 downloads)
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c64club
Posted 7/7/2011 4:38 AM (#58896 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Thanks for photo, Lonnie.
Unfortunately i can't use disc brake nor hydraulic system because of law restrictions. Sidecar is treated as each other trailer. And a "lightweight trailer" must not have "active braking system". Otherwise it needs homologation, that costs more than my month salary. But Police and "Land Transport Supervision" officers don't treat drum brake with cable as active.

This morning i took ride to junkyard and returned home with "treasure" on my trailer:
1. a frame from old couch in warehouse condidtion. Made of 3mm wall rectangular tubing :) Black powder painted :D Perfect base for the project. After removing backrest I will have some spare tubes.
2. some rectangular and round tubes with different walling. Freshly cut 20-40" ones thrown out to junkyard from handrail-maker.
3. struts with ball rod-ends and double twists and nuts for both twists (steering mechanism from some truck).
4. Two dampers from hatchback door.
5. Also got a front wheel fwom WSK125 motorcycle with drum brake, axle, bearings and tire in good condition, only the rim is slightly rusted. It was much cheaper and lighter than aluminium ones (they are from heavy motorcycles)

Overall "kit" weight is about 60 lb. Cost 10$. Love this junkyard. They always have what I need.
Only things they didn't have are rear swingarm and shock absorber(s). But as WSK has both wheels 18" with identical width and axle diameter, this will be easy to find. Local auction/announcement portal is loaded with WSK parts for very few bucks.

So I can't wait for all parts. Cut, drill, grind, weld, paint, GO! Yummy!
Going to do something similar to http://advrider.com/forums/showthread.php?t=680239
Interesting construction. Only one lower mounting. Whole rig is rigid tkanks to four struts. Looks perfect for my bike, as Romet doesn't have full tubing below motor.

Edited by c64club 7/7/2011 7:33 AM
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SwampFox
Posted 7/7/2011 8:23 AM (#58900 - in reply to #58896)
Subject: Re: Lightweight sidecar for 125cc bike



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Location: Summer Grove, LA USA
c64club - 7/7/2011 4:38 AM

... I can't wait for all parts. Cut, drill, grind, weld, paint, GO!....


Please keep us up-to-date. And post pics if you can.
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c64club
Posted 7/7/2011 9:02 AM (#58901 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
I will post pics and descriptions on my site - both polish and english version, and give a link (and maybe some hotlinked pics) here.
Now the wheel is cleaned off rust and coated with mineral rust-protecting paint. I'm searching for cheap swingarm and absorbers somewhere close to my home.
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c64club
Posted 7/13/2011 6:53 AM (#59017 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
I spent last weekend on making additional roof for my workshop (over the parkplace) - parking my rig will be safer and more comfortable.

Wheel is completely painted, brake pads and brake drum matched, tire is weight-balanced.
I've bought swingarm and two shock absorbers in good condition, swingarm is waiting for paint. Cost 10$.
Also bought used upper-arm bolts from some veteran bikes. Cost 4$

Overall cost at this moment - 26$ (incl. painting). There is big chance that it will not exceed 50$ incl. body, lights etc, cause I own many old parts and materials.

Next weekend should be spent in workshop, making my sidecar.


Edited by c64club 7/13/2011 6:54 AM
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Peter Pan
Posted 7/13/2011 8:52 PM (#59029 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Masseltov Igor,
good luck, that MZ did reminded mi to my MZ with superelastic s/c from 86 to 89.
Excellent in winter, but a pain in electrics, thirty like a swedish sailor and every few thousand km you had to bend the frame into shape again.
My 350 Jawa back home in Germany or Poland would be a good rig for back roads, (here its hopeless too weak)
125ccm sounds very week to me, and for a rig allways watercooled is preferable. - think about it

Just stay safe with your construction, Its Your life you risk if you start to build flimsy.
Remind that the Jawa uses excellent tough materials and industrial tubingor chineese bikes are not at all comparable.
May I suggest that before paint you present fotos here and to somebody with experience. Isch, Dneprs and Ural are very heavy, but can serve as reference for where to reenforce.
Best wishes
"Piotr"
Sven Peter


Edited by Peter Pan 7/13/2011 8:55 PM
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c64club
Posted 7/14/2011 3:42 AM (#59034 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
10025
Location: Katowice, Silesia, Poland
I have consulted some things with two guys who ride their rigs frequently. There is one conclusion, also from your post. Bike must be reinforced in few places and the SC frame must be done with redundant thickness in some elements. I can afford to do some parts heavier becaise i don't care about v-max.
I know that 10HP high-rpm 125cc OHV isn't the best motor for pulling a rig, but that's i have. There are two 18HP 250cc OHC motors available for my bike. The same mounting points etc, bigger bore and heavier crankshaft. But their cost can kill. About 600$ for aircooled and about 900$ for liquid cooled. But even if i could afford both them, I will prefer aircooled. Less parts that can be dmaged.
Generally I will try to "copy" that MZ three-points mounted rig.
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c64club
Posted 7/25/2011 5:19 PM (#59212 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Did almost whole sidecar. But now i have problem with bike's frame. It's too elastic. This could bear some test rides but if I'd like to do a rig for regular use i must make my frame way more rigid, especially its rear part.

What idea is better:
1. mount some pipes along with existing ones, or
2. make a sub-frame that combines trhee functions:
-adds rigidity to whole frame
-acts as crashbars (in solo)
-acts as frame for trunks.
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Peter Pan
Posted 7/27/2011 11:23 AM (#59248 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Helo Igor,
Subframe, and perhaps a self made heavy duty back swing.
You should have seen my MZ how often I had to bend everything back into position. (Erich was using the softest boiler plate iron you can imagine)
Sven
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Peter Pan
Posted 8/9/2011 9:54 PM (#59539 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Igor, how is the summer,
bussy swimming or welding?
I was bussy planting trees these days with the help of my Jawa rig.
I look forward for the coming weekend close to the beach (sadly in 4 wheels.)
Sven
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c64club
Posted 8/10/2011 3:16 PM (#59550 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Hey. Few weeks spent on repairing my house and trekking in mountains.
And today - I have just finished mounting other rig. Intruder 1400 with Sputnik sidecar. About a hour ago I was finishing last measurements and adjustments.
Yesterday I did some frame tunning to have it muuuch more rigid. Now the frame doesn't "bounce and flex" in turns or with fully loaded trailer. Doesn't do shimmy with heavy load. Because I earned some extra money, recently I have bought 2-piston Brembo brake with brake pump and cable from crashed Yamaha Skyline. Now my front brake really works and is suitable for sidecar.
Whole rear part of frame is now a kind of "cage", so now rear shoch absorbers don't bend frame in turns.
Back swingarm will be reinforced, but even now it's really oversized.

I will post some pix as soon as i find my card reader.

Edited by c64club 8/10/2011 3:19 PM
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Peter Pan
Posted 8/10/2011 4:49 PM (#59555 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Hello Igor,
enjoy it soon Altweibersommer will come.
It must be a strange feeling working on a 1400ccm and go home to work on 125ccm.But never get impressed. You will be able to pass through the snow where the 1400ccm will not even leave the garage...
Sven
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c64club
Posted 8/10/2011 5:12 PM (#59556 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
10025
Location: Katowice, Silesia, Poland
Working on 1400cc and then returning to my 125cc isn't depressing for me. I like small machines. This work was didactic.
My 125cc will be snow machine. With 3 pcs of Heidenau K41 tires and good gear everything is possible.
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Peter Pan
Posted 8/10/2011 5:53 PM (#59559 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Haidenau is for me CNC equipment.
My first vacation with my MZ rig was new year in Bergen, Norway.
Skol
Nasdarovje
You will enjoy it and I cannot even imagine how the dogs will enjoy it.
Spikes are fabulous!!!!
Make yourself some snow/mud chains!
Sven

Edited by Peter Pan 8/10/2011 5:53 PM
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c64club
Posted 8/11/2011 1:09 PM (#59584 - in reply to #59559)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
Peter Pan - 8/9/2011 11:53 PM
Spikes are fabulous!!!!
Can you explain?

Frame reinforcing is finished. Now I must make new rear brake pedal. Then paint and mount the bike back.
Some small subframe on sidecar, and will be mounted between passenger's and driver's peg holes. Photos should explain whole idea. (grrr. where is my card reader?)
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Peter Pan
Posted 8/11/2011 3:10 PM (#59588 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Spikes = small hardened pines shot into the tire knobs look like stubby nail heads. Forbidden in Germany:
How I know.
05.01.1987 Kiel harbour's custoums officer:
"with spikes you will not enter into Germany!"
Try to find bike tires on first working day in January...

I got a wrong size back tire but none for the front. so I had to pull out each spike from the front tire at -5°C with an unisolated plier from the MZ's stock tool box.

The card reader will apear when you bought a new one....Murphey's law
Good luck
Sven
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c64club
Posted 8/11/2011 5:05 PM (#59589 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Veteran

Posts: 140
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Location: Katowice, Silesia, Poland
Oh, that spikes. In Poland spiked tires are forbidden too. I wonder if it's possible to modify car tire-chains.
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Peter Pan
Posted 8/12/2011 9:56 AM (#59601 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
just search in the achives here. there is an excellent description for how to make fast assembly chain.
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c64club
Posted 8/18/2011 5:38 AM (#59814 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



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Posts: 140
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Location: Katowice, Silesia, Poland
UPDATE. Frame reinforcing almost ready:
http://grzegorski.net/wiki/doku.php?id=en:moto:k125-rama

Edited by c64club 8/18/2011 5:41 AM
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Peter Pan
Posted 8/18/2011 11:02 AM (#59818 - in reply to #58871)
Subject: Re: Lightweight sidecar for 125cc bike



Expert

Posts: 1427
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Location: San Isidro de Heredia, Costa Rica
Hello Igor,
allthough I am not a friend of welding onto a bike's frame. I admit you had a very good idea in closing the frame by a lower detachable double loop.
My experience with the MZ and Jawa acourding to the breaks is following. Mixing systems or styles is a pain.
Mixing hydraulic and mechanic drum breaks in the MZ was including dangerous.
Mixing bar pull and cable pull will result in differences in force and differences in travel gap.
So I am very happy with the Jawa design where both brakes ar drums and both are governed by cable. that way both have simmular gap and force transmition.
In one ocasion this simple and neat design saved my bones.
I was able in a hard lefty t crossing in upcoming trafic and with lifted backwheel to govern the brakes that well that I could circle myself through a "mouse hole" into a side street. (Mainstreet traffic comming, side street traffic waiting and ditch with a deep broken road edge made by the rain)

So my proposal is to make both back brakes with flexible cable.

Take care the day you try to enter Germany, you might meet a custoums or traffic police officer with such bad humor, as I met the day I came back from Norway.
Best wishes
Sven


Edited by Peter Pan 8/18/2011 11:06 AM
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