June 13, 201114 yr I was called the local dahon dealer to find out the fork dropout and material of the D3 curve, to see if I can fit a motor on it... The smallest motor I could find was the 83mm cute motor...(thanks jerrysimon:)) I was not so happy to hear that D3 curve's fork was only 74mm wide, but thankfully I was informed that it was made of cromolly not alloy as I first thougt.. The dealer though, told me -as soon as I told him that I would spread the forks 9mm (possibly up to 11mm to fit the nuts and bolts needed)- that it will not be safe to do this as it will affect the welds and therefore risk a crack!! So I am asking, what do you think is the case? 1) does dahon welds and materials so inferior to bromptons that will indeed be a problem? (I am saying this because Jerrysimon already did this succesfully on his brompton which has a 75mm fork) 2) Is cromolly tougher to spread than steel, so that is the problem? 3) Dealers ignorance and/or repulsion for electric bikes (that are not the dahon boost they sale at a ridiculusly high price) was the reason for discourage me from that project... I want to believe that the right answer is number 3, but I need to know... I am running out of time here, tommorow I sould decide whether to buy the D3 or not and I dont want to buy a bike I will not be able to convert to electric... As he stated all 16/20in dahons has 74mm forks and I think I have seen a lot of front mount dahon conversions in the past... Is there somewere a smaller motor or the did it the same way as I plan? Edited June 13, 201114 yr by Tsakis
June 13, 201114 yr That's a big spread on a short fork. From what I read some car racing doesn't allow cromolly roll cages as poor quality welding makes it brittle, maybe he is trying to tell you something.
June 13, 201114 yr Hi I convert bikes for a living and I would not attempt to convert this bike Look at the Raleigh folder uses the Dahon folding technology under license £349 Raleigh Boardwalk Folding Bike - Boadwalk I would recommend a rear wheel conversion using a rack mounted battery and Kit from BMS china Q100 350W Rear Driving E-Bike Kit - BMSBATTERY 36V10Ah Li-Ion Alloy Shell EBike Battery Pack - BMSBATTERY Allow 6 weeks for delivery and pay by paypal so your payment is safe Frank
June 13, 201114 yr Author Hi I convert bikes for a living and I would not attempt to convert this bike Look at the Raleigh folder uses the Dahon folding technology under license £349 Raleigh Boardwalk Folding Bike - Boadwalk I would recommend a rear wheel conversion using a rack mounted battery and Kit from BMS china Q100 350W Rear Driving E-Bike Kit - BMSBATTERY 36V10Ah Li-Ion Alloy Shell EBike Battery Pack - BMSBATTERY Allow 6 weeks for delivery and pay by paypal so your payment is safe Frank Frank you are always helpful and I know that a rear conversion on a 20in bike is the safe way to go.. The problem is though that my girlfriend is 48 kg and not so strong so weight is a determining factor for this one.. Plus she is in love with that bike, check the pic to see why: http://1.1.1.1/bmi/a2.xe.gr/20110603/193529_112769_x.jpg 16 wheeled bikes with hub gears are hefty indeed for a conversion but again, all bromptons are this way and I ve seen a bunch on the net... I really can't see where the melds are on this fork ( see the photos).... Edited June 13, 201114 yr by Tsakis
June 13, 201114 yr Hi If you want to covert the Dahon Be prepared to cut and add metal and re weld the forks They are so short you wont be able to splay them out I would Buy a spare set off forks and modified them and keep the old front end Frank
June 13, 201114 yr Frank you are always helpful and I know that a rear conversion on a 20in bike is the safe way to go.. The problem is though that my girlfriend is 48 kg and not so strong so weight is a determining factor for this one.. Plus she is in love with that bike, check the pic to see why: http://1.1.1.1/bmi/a2.xe.gr/20110603/193529_112769_x.jpg 16 wheeled bikes with hub gears are hefty indeed for a conversion but again, all bromptons are this way and I ve seen a bunch on the net... I really can't see where the melds are on this fork ( see the photos).... If I was you I'd go for a chain drive or crank drive solution and the pay the extra.
June 13, 201114 yr Author If I was you I'd go for a chain drive or crank drive solution and the pay the extra. any links?
June 13, 201114 yr Author Endless-sphere.com • View topic - Help a DIY newbie - is it safe to spread the forks? Guys at ES seem more confident about this...
June 13, 201114 yr I have a Dahon Broadwalk (steel) and a higher spec Helios as well (aluminium) if you are interested in either PM me
June 13, 201114 yr You mean one guy seems more confident The only way you are going to find out is to try it, nobody is going to give a guarantee though...
June 13, 201114 yr I was called the local dahon dealer to find out the fork dropout and material of the D3 curve, to see if I can fit a motor on it... The smallest motor I could find was the 83mm cute motor...(thanks jerrysimon:)) I was not so happy to hear that D3 curve's fork was only 74mm wide, but thankfully I was informed that it was made of cromolly not alloy as I first thougt.. The dealer though, told me -as soon as I told him that I would spread the forks 9mm (possibly up to 11mm to fit the nuts and bolts needed)- that it will not be safe to do this as it will affect the welds and therefore risk a crack!! So I am asking, what do you think is the case? 1) does dahon welds and materials so inferior to bromptons that will indeed be a problem? (I am saying this because Jerrysimon already did this succesfully on his brompton which has a 75mm fork) 2) Is cromolly tougher to spread than steel, so that is the problem? 3) Dealers ignorance and/or repulsion for electric bikes (that are not the dahon boost they sale at a ridiculusly high price) was the reason for discourage me from that project... I want to believe that the right answer is number 3, but I need to know... I am running out of time here, tommorow I sould decide whether to buy the D3 or not and I dont want to buy a bike I will not be able to convert to electric... As he stated all 16/20in dahons has 74mm forks and I think I have seen a lot of front mount dahon conversions in the past... Is there somewere a smaller motor or the did it the same way as I plan? Hi, I don't think dealer tried in any way to put you off from this project. I agree with a dealer here that 11mm is a wide spread tough cro-moly unlike alloys is a lot more flexible. From the dealer point of you he has to be professional and I'm not surprised he said he wouldn't do that. What would happen if he told go for it and then the welds crack and someone gets injured. I'm sure you wouldn't be very pleased. In this case I'll back up the dealer and I think he gave you right advice and don't think he had any intentions in putting you off doing this project. All the best Andrew
June 13, 201114 yr Author Well I dont mind cracking the welds while I am doing the spreading... I dont wont to risk my girlfriend from the unpleasant situation of a cracked weld while riding... If I manage to spread it with no cracks it will be a problem afterwards?
June 13, 201114 yr I worried about this when I did my Brompton forks. Initially I spread them further nearer 100mm (before I was able to get my motor down to 80mm), widened the dropouts and made the holes for the safety washers bigger. As I did it I was shaking. It is all in my DIY conversion post step by step. I did however read up a lot about it and knew it had been done safely by many before me. If you read some suppliers of Brompton conversions they talk about supplying professionally modified forks. NRG is right, in the end you either go ahead and try it based on a valid assesment of what you have read and experience out there of it being done safely or not. In your case for this bike, I am not so sure there is as much evidence that it will work safely as there is for the Brompton. In the endless sphere post some seem to be advising that you can source different forks that may be better. I doubt anyone here, or on endless sphere, will give you the guarantee that you may be seeking. In the end it is YOUR own decision and YOU must therefore take responsibilty for it. This is probably made harder for you, as you say, in the fact that you are doing this for someone else. Regards Jerry Edited June 13, 201114 yr by jerrysimon
June 13, 201114 yr Here is another option, though with a heavy weight compromise, that would not require any fork spreading. Crystalyte Europe :: Motors :: 209 Front wheel brushless motor 16"-20" rim Also I noticed it aint cheap! Regards Jerry
June 14, 201114 yr Author Not chap at all.. On the other hand I might be able to find a tongxin nano and gain 3mm..
June 14, 201114 yr Author http://www.flickr.com/photos/icomunete/872320858/sizes/z/in/photostream/ All sizes | dahon_fork | Flickr - Photo Sharing! Dahon Folding Bicycle Forums > Front Hubs This guy here spredded his broadwalk fork (also 74mm, also cromoly) to 100mm(!).. A shop named Harris Cyclery did the job... I understand that a fork made for 20in wheels is longer than a fork made for 16in but here we are talking about a whooping 26mm!!!! Maybe I should find a proffesional here is Greece...
June 14, 201114 yr http://www.flickr.com/photos/icomunete/872320858/sizes/z/in/photostream/ All sizes | dahon_fork | Flickr - Photo Sharing! Dahon Folding Bicycle Forums > Front Hubs This guy here spredded his broadwalk fork (also 74mm, also cromoly) to 100mm(!).. A shop named Harris Cyclery did the job... I understand that a fork made for 20in wheels is longer than a fork made for 16in but here we are talking about a whooping 26mm!!!! Maybe I should find a proffesional here is Greece... Heating the forks may make it better but then you need to be careful they are cooled at the right rate to keep the strength required. A bike shop may not be the professionals you need, I don't know about companies but I'd probably start by finding a metalwork teacher to ask.
June 14, 201114 yr Author Heating the forks may make it better but then you need to be careful they are cooled at the right rate to keep the strength required. A bike shop may not be the professionals you need, I don't know about companies but I'd probably start by finding a metalwork teacher to ask. I don't have access now but I found it yesterday while searching, some expert guy stessed that you must do this kind of procedure without heating in order to success.. I will try it, but I will do more research in case there are pro tools for this..
June 14, 201114 yr I don't have access now but I found it yesterday while searching, some expert guy stessed that you must do this kind of procedure without heating in order to success.. I will try it, but I will do more research in case there are pro tools for this.. Could you not clamp the forks near the top and spread them along the length of the tube thereby taking the stress away from the welds? Of course that introduces the risk of collapsing or kinking the tube but it doesn't sound like you need to bend them very far so I would be surprised if that happened, particularly if you spread them slowly with a threaded rod. The other problem is having to support the tubes and that would require some sort of jig.
June 14, 201114 yr I am an engineer and work extensively with different metals. My advice would be to modify your existing fork by heating both legs of it near the crown using a blowtorch until they are starting to glow red a little. When the fork legs are hot bend them outwards a little and you will have no risk of cracking the welds. You would have to repaint the fork afterwards, that is the only disadvantage of the method I am suggesting. Also, if you use this method. when you have heated the forks and bent them allow them to cool down slowly. Do not quench the heat from them quickly (for example by dipping them in water) or you could make the metal go brittle.
June 14, 201114 yr I am an engineer and work extensively with different metals. My advice would be to modify your existing fork by heating both legs of it near the crown using a blowtorch until they are starting to glow red a little. When the fork legs are hot bend them outwards a little and you will have no risk of cracking the welds. You would have to repaint the fork afterwards, that is the only disadvantage of the method I am suggesting. Also, if you use this method. when you have heated the forks and bent them allow them to cool down slowly. Do not quench the heat from them quickly (for example by dipping them in water) or you could make the metal go brittle. +1 (random ahdfarhe)
June 15, 201114 yr I am an engineer and work extensively with different metals. My advice would be to modify your existing fork by heating both legs of it near the crown using a blowtorch until they are starting to glow red a little. When the fork legs are hot bend them outwards a little and you will have no risk of cracking the welds. You would have to repaint the fork afterwards, that is the only disadvantage of the method I am suggesting. Also, if you use this method. when you have heated the forks and bent them allow them to cool down slowly. Do not quench the heat from them quickly (for example by dipping them in water) or you could make the metal go brittle. Does heating for short periods of time adversely affect the strength/properties of cold drawn chromolly? (Assuming the tubing is cold drawn) I understood the annealing or normalisation process involves keeping chromolly at high temperatures for 15 minutes and then letting it cool down in air.
June 15, 201114 yr As it stands the grain structure in the metal is an annealed state, assuming they have heat treated the forks after welding them in the first place. Heating the metal and then cooling it slowly should not cause a significant change to the grain structure or strength of the metal.
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