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Converting a 2009 Dahon MU SL to 18 speeds?

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Converting a 2009 Dahon MU SL to 18 speeds?

Old 07-09-14, 12:52 PM
  #26  
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For anyone that has done this kind of conversion using a braze on adapter; how did you do the cable stop? I see reference above to an under BB cable stop but no details?
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Old 09-20-15, 10:47 PM
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don't know if this is still active, but the derailleur mount has a cable stop built into it's bottom side (ie. inferior side). It is really quite simple, you just have a lot of cable/cable housing going all the way under the bottom of the bottom bracket housing. Thor says to use zip ties, which worked great for me. not perfect, but great.

don
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Old 03-13-18, 04:11 PM
  #28  
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I just got a Litepro P adapter for 41mm seat tube, but the braze on part is badly designed and FD's won't fit it in, because the slot on the braze on is too short, and the bottom of the slot slot ends with a solid lump that hits the FD mechanics. Also the braze on is too far back.

Anyone have the same problem?

I'm looking at the photos of the K adapter version, and the braze on for that one is much longer and the slot is cut all the way down to the clamp. It's also much further forward, and would have probably worked if I had that one instead, switched with the 41mm clamp.

With the P adapter, I measured the braze on center is 28.3mm from the center of the seat tube. Shimano guide says it should be 24.5-25.5mm, so that's a difference of around 3mm of clearance to the inner chainring, which is supposed to be at around 39mm. If I hold the FD directly against the seat tube, the center of the mounting screw would be at 26.5-27mm, which is 1-1.5mm further out than the Shimano guide recommends, and it just barely fits without the chain rubbing against it.

I'm going to try printing out the braze on part in plastic to see if I can get it to work with the litepro clamp.



Image linked from Hands On Bike
Hands On Bike: Journey of the Boardwalk: Part 16 - Front Derailleur for the Dahon Boardwalk TT

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Old 03-20-18, 08:14 AM
  #29  
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So here is the problem with the P type adapter. The slot is too short and I can't get the FD into it. Also the solid block below the slot, and the fact that it's angled backwards hits the FD mechanics. The same problem might happen with the K type adapter for the FD4700 and FDCX70 because both have the mechanics further forward, but some photos of the K type adapter seem to show it working with the FD5700 which has the mechanics further back. The K type also doesn't have this solid block angled backwards.



The other problem is that the P type is angled too far back. I measured 24 degrees back from the seat tube. I think the K type appears angled further forward but I don't have one so I can't measure it. The seat tube/chainstay angle is around 82-83 degrees. This means the P type is 83-24 = 59 degrees. This is angled too far back and the chain is rubbing on the top of the FD cage when on the big-big combination.

FD4700 spec 61-66 for 52T shorter cage
FDCX70 spec 61-66 for 52T shorter cage
FD5700 spec 63-66 for 56T longer cage

Also, the P type position is very far back. The K type is further forward with the attachment slots flipped to the opposite side.






I decided to make my own braze-on to attach to the Litepro 41mm diameter seat tube clamp. It took me (too much) time, 4 days straight to 3D print and test several prototypes with ABS FDM. I tried a few different angles but settled for 66 degrees, which is 17 degrees angled back from the seat tube. My theory is that the further forward I can get the FD, the less problems I will get with the short chainstay and sharper sideways chain angles rubbing on the sides of the FD cage, but I can't confirm this. Also having the FD angle more parallel to the seat tube makes the cable pull angle more parallel to the FD pull arm. The angle of the cable will affect the length of the pull, and the direction of the stress on the braze-on adapter.

Also, Shimano documentation shows braze-ons 8mm forward of the seat tube center line, when the seat tube is directly on top of the BB shell. The Litepro P type is much further back. The K type might be in the right place.

Additionally I decided to place the clamp above the FD because when it was below there was some contact with the sides of the cage. This means I can't use the built in cable stop on the Litepro clamp. I would need a different cable stop.

The plastic is too weak and will bend so I can't test how well the shift is performing because the cable pull keeps changing. I ordered outsourced prints of nylon SLS which should arrive later this week, which is much stronger and less brittle. I also ordered prints in steel bronze/infused which will take 2 weeks to arrive. I'm not sure about how strong the metal is so I oversized the thicknesses, although it might pass 150g in weight. The steel bronze/infused is like steel powder glued together, with the glue later replaced by bronze infusion, but there is a chance that the bronze doesn't pass through uniformly and weak spots develop.

Alternatively, aluminum SLM printing is much stronger where the aluminum powder is directly melted together with the laser, but costs twice as much.








I also used the Avid Rollamajig to change the FD cable angle by 90 degrees and route it from the left side. There is a solid plate welded between the chainstays that prevents the cable from going under the BB shell.



I'm using 46/28T chainrings, and since the typical compact is 50/34T or normal 53/39T, this may be why the litepro adapter is angled further back, because the 50T ring is 8mm higher than the 46T, and 53T is an additional 6mm higher. At this height, the FD might hit the seatstay when it's too height. Also, if you are using larger than 46T, the Shiimano FD4700 probably will not fit because it has a really long pull arm. I only have 3-4mm clearance between the pull arm and the seatstay on the Vigor D9.

Last edited by tomtomtom123; 03-20-18 at 08:47 AM.
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Old 04-03-18, 01:32 PM
  #30  
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The steel prints arrived but they're heavy. The pair weighs 140g. I could have used a thinner model and made it 90g but I was worried about it being brittle, so I oversized. Aluminum print would be 40g but costs twice as much. Maybe next time. I also got the angles a little bit wrong. The cable is 5-10 more degrees further than where I modeled my cable stop. It just means that the plastic nipple on the Avid Rollamajig might wear out sooner. Also, the FD came out as 66 degrees but the chain sometimes rubs on the tail. It may have been better at 64 degrees.

SLS nylon is also surprisingly strong. It might actually be strong enough, but it flexes around 0.5mm.













The amount I've bent my FD cage.



Bigger image of the Litepro P type fit problem. The braze-on slot is too short so the FD won't fit in it, and the front of the coil spring mechanics hits the angled back part of the P type adapter. It probably won't work with any of the Shimano FDs. Maybe with a SRAM FD.



I had to shave off a corner of the Litepro clamp that I used for the cable stop and reverse the direction of the screw by drilling out the threads and changing from M4 to M5 screw and adding a nut, so that it would fit.



I tested a 46/26T double and it seems to work fine from gears 1, 2, 3. On 4, I have to press the shift lever past the index until the upshift is complete. Above 4, it will not shift because the bent I put in the cage makes it too far away to press the chain against the larger chainring when shifting from small cogs.

The long pulley arm of the FD-4700 just barely fits under the seatstay of the Vigor with 46T. It probably cannot fit a larger chainring. The Speed type frames have a higher seatstay. You could use a short pulley arm like on the 5700 or FX70, or SRAM FDs, and probably go up to 53T. I think it cannot go lower than 44T or else the tail of the cage will hit the chainstay.

I have read that the SRAM Rival and Force 22 FDs have a yaw feature that twist the cage between the 2 index positions. I might try it next time if the one I have now fails. This might solve the cage angle issues that I have, however the trigger for these FD's have no trim positions and I don't know how much clearance they give at the front of the cage. Also, the frame specifications manual states that it needs a clear space of up to 16mm from frame center for the spring coil to swing, which seems really wide. I'm not sure if this will create problems since the 41mm seat tube is 20.5mm from frame center.

With the bent cage, I can get the inner chainring to 40-40.5mm from frame center. Normally it is at 39-39.5mm for a double. The FD is mounted +3mm further out from the frame center than normal (seat tube is also +3mm wider [41-35]/2=3mm), so if you want to use the normal FD angle without having to bend the cage wider, you'd have to space out your cranks +3mm, but this increases your Q-factor and is probably too much distance to space out if you use an integrated spindle crank like a Hollowtech II.

Most likely a triple FD won't work because it needs much more clearance for the spring coil to swing, which the seat tube interferes with, unless you push out both the braze-on mount and chainline further out.

Last edited by tomtomtom123; 04-03-18 at 01:39 PM.
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Old 04-03-18, 03:16 PM
  #31  
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Re 25th post, BB Shell threaded to Asian/British standard..



As the seat post tube telescopes past the BB, behind it , the way a FD fits is also Different than a Braze on to a conventional bike ..

I got a clamp on bracket to do similar for my Brompton, for Italian style Braze on FD to fit a double chainset.
its fabricated, brazed together, then black gloss powder-coated..

Then Got a 2 speed internally geared crankset instead.. with my 3 speed..
The Shifting Both at the same time , works well better in fact, as the big reduction geared crank has a double shift
between high in low range and low in high range ..3rd to 4th of 6.

If your DaHon has a rear derailleur, then the front derailleur should be OK.. both have to be spinning to shift..






....

Last edited by fietsbob; 04-03-18 at 03:25 PM.
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