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Home Forums Sidecars Sidecar Builds R75/6 sidecar subframe

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  • #5723

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    The rear frame on these bikes are bolt on and very light so they need to be strengthened when a sidecar is fitted.

    This site is not allowing me to attach images. I have followed your instructions. after I choose the file, and add attachment, I can see it is uploading to server, but then it disappears, and the button does not change to give me the option of remove or insert to post.
    I was able to achieve this on my one successfull post , but maybe now you have changed my status so I can’t post a photo:huh:

    #5821

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    Hi Coriman.

    Are you using a PC or Mac and what web browser are you using?

    Also what is the filesize of the pictures you are trying to load?

    Eddie

    #5823

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    Picture of the Rear bolt on frame, which is very weak for a sidecar and not recommended without additional strengthening.
    OLYMPUS DIGITAL CAMERA

    I fabricated an under seat sub frame to stiffen the top of the rear suspension units. You lose the tool tray but gain a sidecar.
    OLYMPUS DIGITAL CAMERA

    The frame was cut from 50×50 angle and fully welded but do not weld to frame use high tensile bolts. Cap screws are the strongest.
    OLYMPUS DIGITAL CAMERA

    The top suspension bolts are substituted with long cap screw which pass through the units and right trough the fabricated box section, which have internal side wall bracing tubes, so you can fully torque the fastenings without crushing the box section.
    OLYMPUS DIGITAL CAMERA

    The bolts in the picture are low grade just for temp jigging the job. I will post more info later.
    [hr]
    To continue, as this was prototype work minor fitting mods happen during the build but here is the first stage in place. It does not impact the seat, and is above the battery box, which needs to be installed prior to the rear mudguard .
    OLYMPUS DIGITAL CAMERA

    The lower engine mounted sub frame is cut from 10mm plate, and held in place by the engine mounting bolts. Cutouts are made for the gear lever and frame tubes. This plate goes behind the exhaust so this can be moved out at the rear clamp by 10mm for clearance.
    OLYMPUS DIGITAL CAMERA

    The bottom plate carries both front and rear sidecar mounts, and the tail is extended up behind the muffler at an angle, then another fabricated plate is welded to that , which mimics the passenger footrest plate on the bike.
    OLYMPUS DIGITAL CAMERA

    The front of the plate is fabricated into an open box section for strength. and the sidecar mounting bosses are bolted on front and rear.There is and addition diagonal under brace which attaches the rear of the lower plate to the opposite side lower bike frame member.
    OLYMPUS DIGITAL CAMERA

    On the last picture on this page you can see the lower plate fitted with the rear lower side car attachment boss which take the standard sidecar threaded fittings. Also note how the plate wraps around behind the muffler and the strengthens the passenger footrest plate. The foot rest then locates both.
    OLYMPUS DIGITAL CAMERA

    I have added another frame tube outside and parallell to the original, which is bolted to the top of frame and suspension unit , and again bolted with high strength cap screw to the bottom plate to give torsional rigidity, since the original frame pate is the thickness of your little finger. Ok for solo just , but no good for side car forces.
    I will tell more on another post. Note Do not weld onto the bike frame itself.

    #5824

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    Build continues here are some photos of the fixing points and set up.

    The idea is to get the front and rear mounts as far apart as you can, and the top and bottom mounts as far apart as practical.

    Sidecar wheel lead is important for handling and stability I set mine at 300mm in front of the rear centre to centre. with 35mm toe in measured at the front wheel spindle

    Lean out of the bike away from the chair varies but I set mine at10mm at the top of the wheel rim. This varies with the suspension set up and weigh of the rider etc.

    The chair frame should be sitting parallel to the ground

    The object of the exercise is to be able to modify and fit whatever you need for set up with out upsetting the bike or cutting body panels

    Once its all together you hardly notice the sub frame.
    I will post more on this later.

    #5825

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    Tuning up the rig is important for good performance.
    Suspension sag, spring rate, head stock bearing pre-load, wheel bearings , fork bushes, handle bars, lean out, wheel lead , toe-in, all need to be set correctly, and while there is a rule of thumb for everything the well tried system of set test adjust feel and re test adjust, has to be done.

    These picture show my rig with the original BMW bars which wer only 650mm wide. (BMW bars are 22mm diameter not 7/8 inch) which are more popular and cheaper to buy.

    I converted mine to 7/8 which allowed me to use a 900mm wide ventura touring bar Ah La Triumph. They are 9 thou bigger in diameter so the controls need to be opened out to accept the new bar diameter, and the switch cables cut and lengthened.

    The left hand control is positioned in the picture above in the original bar width , whereas the right control is in the new position having been rewired. BMW high bar throttle and brake and clutch cables work well, so I just replaced then with new .

    The picture above shows the new wider bars. I am able to ride this rig thru town and take my hands off the bars and she will track perfectly straight, also I do not need a steering damper as I have no low speed wobble. If I hit a bump in the road it can induce a small wobble but as soon as i just rest my hands on the bars it stops. Low speed handling is brilliant, but I need to reduce steering effort in the 80-100km/hr corners. So that’s just another continuation of this project that I am going to sort out with front wheel steering geometry.

    Trail needs to be reduced, and I will reduce this by moving the wheel forward in relation to the projected steering angle, and this can be done in several different ways. So right now I am researching the most cost effective way to achieve this. To be continued.

    #5865

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    After a lot of research I have decided that the most cost effective way for me to reduce trail is to rake the forks, so I have made a 3 degree top yoke.
    BMW Top Yoke 3 Degree mod

    The wheelbase is increased reducing trail from stock 90mm to 48mm.

    This shows the new fork rake at 3 degrees from steering head angle.

    Steering effort is much reduced, but I am still keen to increase rake further and there are a few clearance issues to consider around the headlight and steering head, as the fork tops are moved back.

    #5866

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    Thanks Coriman, I’ve lots of questions now

    The stock yokes are designed to line up for the forks to pass through both yokes in a straight line.
    If the holes in the top yoke are moved does that mean the fork staunchion is passing through the lower yoke on a slight angle?

    If so how does that effect the clamping of the staunchions, can it cause any damage or slip?

    With the aftermarket top yoke on my bike, Do you know if there are any parts I’d be missing if I was to a change to a factory or Coriman 3 degree offset top yoke?

    Are you able to make a 2nd yoke with the 3 degree or whatever offset? I’d be keen on one. but I’d need it in the next 2 weeks to make Cold Kiwi on the bike.

    #5867

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    The stauntions do not pass throught the top yoke.
    The top plate has to bend at the stem nut by 3 degrees. This is a progressive twist though the plate so you can’t see it, but all three nuts have to clamp flush.
    The bottom yoke is the fulcrum point of the fork. The top is movers 15mm which moves the wheel spindle 42mm at test with about a 3 to 1 Ratio. The Alloy bottom yoke is 26mm thick at the clamp, so in theory it has to accept a 3 degree fork rake over 13mm each way.
    The distance between yokes is 180mm so the required rake at the lower clamp equals 1.08mm each way. Since the alloy yoke is malleable it can tolerate the change in rake when the clamps are tightened. The rubber grommets at each end of the ears confirm this as they still fit perfectly.
    Re parts, I am not sure whether on your bike you have a rubber mounted instrument bracket that fits to the front riser studs.
    Also the type of fork nut changes on the R80 before of after 1985 I believe. The stock top plate on /6 etc has a 33mm stem nut locating hole and a 30mm stauntion fork nut hole. You should be able to check dimentions against may scanned A4 images and scale up or down. I could make you one in time, but they are hand made and it takes quite a few hours so I would have to charge you NZ$125. Let me know what you want to do.:idea:

    #5868

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    Thanks for that.

    The instrument bracket is rubber mounted and does mount via the front riser studs. I’ll have to google/physically check the stem nut and fork nut dimensions. My sidecar is at the brother in laws place about 20km away so I’ll see when I can get over there and measure up but I’m very interested.

    #5872

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    I did a bit of measuring last night, there’s some new pics in my thread.

    Long story short the Steering Stem hole is 33mm, the thread at the top of the fork staunchions is 26mm but I didn’t have anything on me large enough to remove the fork nuts to measure the staunchion hole.

    If 3 degree rake allows your offset top yoke to be mounted without requiring modifications to the surrounding fittings then I’d like to get one of those off you. As soon as I have a bank account number I can deposit the money.

    #5873

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    I have to make some assumptions here, which can be dangerous.
    The stem nut hole is 33mm, that”s good the hex nut is 36mm AF.
    My nut is domed and so I had to cut the op off it to clear the underside of the handlebars. (Depends on riser height).
    Riser stud holes are at 32mm centres. Are you risers though bolts or studs from the top. The nuts are a tight fit around the steering head, but can be done with an open ender. I intend to make new risers later for mine with a pull back and cap screw fastened, so I don’t have to turn the nuts under the yoke (easier and stronger).
    Stauntion hole centres are 182mm but the critical missing dimention is hole size. The securing nuts have to be a nice running fit in the yoke, so we have to be sure of the top yoke hole size, ie. the yoke bearing surface under the hex and above the thread. If it’s 30mm we are in business. We need to do some research to see if your model stock yoke is the same as my model stock yoke. I will check out your pics.
    Cheers
    [hr]
    http://www.motorworks.co.uk/vlive/Shop/Parts.php?T=3&NU=10&M=20&Ct=KA

    These guys show secondhand parts for different models you can see the changes in fork nuts and top yokes
    Check it out which is your model?

    #5874

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    I don’t have the original top clamp but looking at the motorworks site it should have been this one

    Used – Top yoke plate | STR52135
    Fits R65 Mono, R65RT Mono, R80 Mono, R80RT Mono, R100RS Mono, R100RT Mono
    t.gif

    My Steering stem nut is also domed and fits under my handlebars which have 50mm risers, though it only just fits when fully unthreaded.
    The risers use bolts that pass all the way through with separate nuts on the underside. I use an open ender underneath as I can’t get a socket on the nut, and I tighten from the top.

    I’ll have to find something big enough to take that top nut off the staunchion and check out the hole size etc, but I might not be able to get over there again till Saturday afternoon.

    #5875

    Coriman
    Participant
    • Location:
    • Bike:
    • Rank: 125cc Rider

    That’s all good, basically the handlebars end up more over the top of the nut because the stem is 15mm further forward.
    Iv’e just bought some new fork gaiters from motorworks 10 pounds each . They are $136 dollars each in NZ they are excellent to deal with. They would have second hand indicator brackets etc if you need them.
    Contact me when you know whats what , as those fork nuts are critical.
    Cheers Phil

    #5876

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    Which gaiters did you get? I want some and I’ve seen many differing opinions on whether the 11 or 13 rib ones are more suitable.

    How long did it take from ordering to receiving them and what was shipping like?

    I contacted Kane at RTwin in Palmy and he quoted $35 each for gaiters and $30 for an indicator mount with $8 postage.

    #5878

    Eddieb
    Keymaster
    • Location:
    • Bike: Suzuki DR650 ADV
    • Rank: 1200cc Rider

    The Staunchion holes are 38mm

    Pics etc here: http://www.flyingthechair.co.nz/showthread.php?tid=5&pid=229#pid229

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