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Downtube folding bike

Old 06-30-20, 08:11 PM
  #2326  
PacificSpray
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Downtube 11H electric FWD conversion

My wife has abandoned her MTB and now only rides the 11H. We mainly tour and utility cycle. Shopping is 25km away, with a strong headwind common. She wants to tame the headwind and use the car less for shopping and library visits. The 20" FWD Dillenger kit has crossed my radar.
I see comments about suspension/aluminium forks being 'unsuitable' due to dropouts failing. The Dillenger is only 250W and I would use a torque arm (or two). I could ask Yan to send me a rigid fork, but it is still aluminium.
What do you think?
TIA.
Walter
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Old 07-03-20, 09:54 AM
  #2327  
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Since Bromptom sells a front motor for their bikes, as does Citizen, a 250W motor on rigid, perhaps Cr-moly forks must not be a liability. Being a worry wart retired engineer, I went with rear motors when I motorized our Downtube Nova and 8FS in 2017, It would have been a shame to lose the front suspension on the 8FS.

There's a dearth of pre-packaged ebike rear drive kits for 20" bikes. I had some prior experience with conversions so I bought everything piecemeal (motor, rim, spokes, electrical parts, battery) and put it together. Not much space for batteries on a folder. I use smaller 36V 10AH pack, good for 30 miles at folding bike speeds. However, you probably can find an inexpensive electric folder for less than the parts for an electric kit, let alone the donor bike. Then you can spend the money you saved on upgrading the cheap parts on the inexpensive electric folder!

Here in the USA, I haven't seen any low cost e-folders I like (heavy), but the Qualisports models at around $1000 USD seem attractive with their lighter weight and low visibility seat tube batteries. My Nova is 36 pounds and the 8FS is 39 pounds after conversion. We rarely fold them.

When my wife had troubles getting on/off her 8FS, i looked for a step-thru folder. I really liked the CItizen Barcelona, and it has a steel fork, but I still prefer RWD, and that would nean chucking out it's 3 speed hub. I bought a low cost Schwinn Loop instead. Put on a rear motor. Replaced the seat, tires, pedals, crank, steerer tube and bars. So now we have three.
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Old 07-03-20, 04:08 PM
  #2328  
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Originally Posted by Doc_Wui
Since Bromptom sells a front motor for their bikes, as does Citizen, a 250W motor on rigid, perhaps Cr-moly forks must not be a liability. Being a worry wart retired engineer, I went with rear motors when I motorized our Downtube Nova and 8FS in 2017, It would have been a shame to lose the front suspension on the 8FS.

There's a dearth of pre-packaged ebike rear drive kits for 20" bikes. I had some prior experience with conversions so I bought everything piecemeal (motor, rim, spokes, electrical parts, battery) and put it together. Not much space for batteries on a folder. I use smaller 36V 10AH pack, good for 30 miles at folding bike speeds. However, you probably can find an inexpensive electric folder for less than the parts for an electric kit, let alone the donor bike. Then you can spend the money you saved on upgrading the cheap parts on the inexpensive electric folder!

Here in the USA, I haven't seen any low cost e-folders I like (heavy), but the Qualisports models at around $1000 USD seem attractive with their lighter weight and low visibility seat tube batteries. My Nova is 36 pounds and the 8FS is 39 pounds after conversion. We rarely fold them.

When my wife had troubles getting on/off her 8FS, i looked for a step-thru folder. I really liked the CItizen Barcelona, and it has a steel fork, but I still prefer RWD, and that would nean chucking out it's 3 speed hub. I bought a low cost Schwinn Loop instead. Put on a rear motor. Replaced the seat, tires, pedals, crank, steerer tube and bars. So now we have three.
.
Thank you for your considered response.
My post may be more suited to an eBike section; perhaps a mod will deal with it appropriately. I'm new at this, so I'll do the polite thing and introduce myself properly.
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Old 08-08-20, 09:50 AM
  #2329  
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All,

It is a sad day.

My 9FS just suffered a fatal injury.

This bike was purchased new in 2009 and was my ace number 1 foldup.

I took it on a grocery store run this morning. (I always look for a reason to ride this bike).

After I got home I noticed the seat post tube cracked, probably due to my 250lb weight, the leverage of the extra long seat post and the weight of items in rack.

I'm sure I stressed it beyond any design specification for 11 years. Yan, you make a good product that took my abuse for 11 years.

Not sure what to do. But for now am doing nothing.

Am in mourning, it got me home, so it died a hero. Good bye my friend, may your organs be recycled to the next generation.



2017

last month Annapolis, Maryland

Today, the last ride.

Fatal crack.

Last edited by mirfi; 08-08-20 at 11:19 AM.
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Old 08-08-20, 11:17 AM
  #2330  
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How much seatpost actually extended down into the frame tube? It seems odd the frame would break there unless there was a very minimal seatpost inserted.
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Old 08-08-20, 11:28 AM
  #2331  
mirfi
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Originally Posted by unikid
How much seatpost actually extended down into the frame tube? It seems odd the frame would break there unless there was a very minimal seatpost inserted.
Where the seat post is clamped is a smaller diameter than below. So there is some tiny "wiggle" room. Seat post is plenty long and probably extends 6 inches into the tube.


Don't know if you can see it, but the crack is where the tube diameter changes. Bigger below the crack.
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Old 08-09-20, 07:52 PM
  #2332  
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I see what you are talking about now. I cannot understand why anyone would design a frame that way . That seems like a failure waiting to happen.
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Old 08-09-20, 09:02 PM
  #2333  
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The owner of that bike company claims to be the designer, whatever that means, but clearly any engineer would have given that detail a hard “pass“.
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Old 08-09-20, 09:16 PM
  #2334  
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04, Old thread, it Break down Yet? I see that orange one is toast..
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Old 08-09-20, 11:07 PM
  #2335  
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How far is seat tube inserted?

How far in the frame did you insert your seat post? I extended my custom seat post to below the lower angle gusset so that the post had a length in which to couple out the bending force. If yours just engaged the short length of frame above the main frame rail, it's no wonder it broke.
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Old 08-10-20, 04:31 AM
  #2336  
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downtube
Yan will be along any minute....
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Old 08-10-20, 02:37 PM
  #2337  
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Originally Posted by flyboy2160
How far in the frame did you insert your seat post? I extended my custom seat post to below the lower angle gusset so that the post had a length in which to couple out the bending force. If yours just engaged the short length of frame above the main frame rail, it's no wonder it broke.
See mirfi's answer and pictures above - 6 inches. It is visible that the seat tube suddenly gets wider where all the welds happen. So the rest of the seatpost down below isn't touching anything. That explains the crack right above the welds.
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Old 09-10-20, 11:48 AM
  #2338  
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All,

When I made the post about the damage, Yan got in contact with me. He stands behind his product. Nonetheless, I felt I had to attempt to fix it. And if it doesn't fix, I'll look at a new one.

(But let's face it, I put 250+lbs, plus whatever is in my pack and basket on an extended seatpost/tube. And then put it on a bouncy bike. Something had to give eventually).

So, the son and I made a sleeve from a piece of fence top rail. It fit in the lower part of the seat tube from the bottom. The seat post also fit in this pipe. To get them all together we took a slice out of a 6inch 'sleeve' and wooden hammered all these parts together. We them welded the crack, (ugly). Wish we had taken pictures along the way. Note: we attempted numerous other fixes.

My fat ass took this bike on a hilly two mile ride to the grocery store about an hour ago. Seems to hold up. Note: we hope to never take this apart.



Fits in seat tube, seat post fits in it. Thickness is 16 gauge.

"Sleeve" goes down about an inch below here. Very solid.
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Old 09-10-20, 02:54 PM
  #2339  
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That looks like a creative solution! What is holding the sleeve in place? Friction? Loctite? Or did you somehow manage to get it welded in as well?
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Old 09-10-20, 05:18 PM
  #2340  
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Originally Posted by unikid
That looks like a creative solution! What is holding the sleeve in place? Friction? Loctite? Or did you somehow manage to get it welded in as well?
Friction. We had another long piece of pipe with the same O.D. (smaller I.D.) as the sleeve. So we used that pipe to push the sleeve up into place. And we kept it there as we pushed (kinda screwed) the seatpost down into the tube/sleeve. We did put a small bevel on the inside of the sleeve and on the outside of the seat post where they would meet.
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Old 09-11-20, 05:27 AM
  #2341  
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Originally Posted by unikid
I see what you are talking about now. I cannot understand why anyone would design a frame that way . That seems like a failure waiting to happen.
Mirfi have 120kg and uses a extended seatpost and a seatpost rack.

Its far beyond any bikes limits.

A bike for him need to be a diamond shape frame with extra reinforced joints and welds, witch is not the case of danotube cricket
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Old 12-02-20, 09:33 AM
  #2342  
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I've been gone for a while to deal with personal matters. Thankfully all seems good now.

I agree that the frame pictured was imperfect. There are a couple points:

1. The frame is over a decade old. I don't believe there was anything from that generation that was as tough. The user states. "I'm sure I stressed it beyond any design specification for 11 years. Yan, you make a good product that took my abuse for 11 years."
2. I tried to have the factory modify the seat tube area for years. I don't recall why it took so long for them for make the required mods....but it was much longer than expected. The current frames are much stronger.

Thanks,
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Old 02-17-21, 01:57 PM
  #2343  
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Hi I'm spent numerous hours thinking of my next bike purchase. Among other nonfolding otpions,
for the folding category, i'm between a downtube XFS and the 8H model (possibly zizzo liberte), but leaning towards the XFS because I think if I like it, I'd spring for the miniB to get the IGH and gates system and easy ability to fly with it.

My few remaining concerns about the FS and in general Downtube bikes:
1) I've never seen anyone push or trolley the bikes along, which means to me that it's a PITA to. I suppose it's not the biggest end of the world but I'm wondering why Yan hasn't implemented something like tern's rapid transit rack or the easy wheel presented here....It must not be really demanded.
wwwDOT******DOTcom/r/foldingbikes/comments/jqmksb/i_went_to_the_grocery_store_today_with_my_little/
(I don't think i can post links yet)

is there any aliexpress aftermarket rear racks that have these trolley wheels as seen in tern's rack?

2) how much extra maintenance is needed with the addition of the rear shock? Will I or my LBS easily able to replace it when it wears down?

3) how easy can a rear (nonseat) rack be attached?

thanks all
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Old 02-18-21, 01:52 AM
  #2344  
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If you are thinking of air travel, he does have the bicycle suitcase. He does mention that if you want to put a full suspension bike, you’ll need to deflate the tires. The other 20” and smaller bikes should fit w/o doing this

If you have questions, you should call Yan directly. I called him last year about buying a new bike to replace my 8H which had been stolen off a bus rack. (I didn’t know the gov’t was going to send everyone $1200 or I’d have purchased another 8H. I much prefer IGHs to derailers.) I was considering the minib but Yan said he only recommends that for lightweight riders, e.g., 120 lb. or so females. So I purchased a Nova, but I really prefer the 8H except that it’s heavier. Yan is generous with his time. I talked with him for about an hour.
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Old 02-18-21, 06:34 AM
  #2345  
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Lance,

I never had any issue rolling the 9FS around when folded, plus it had that super functional stand under the bottom bracket to keep the chainwheel off the ground.
But note, when I go shopping with it, I throw it in the cart (WallyWorld) or at the grocery store I leave it unfolded, just turn the handlebars 90 degrees, fold pedals and shop around until the basket is full.

As for
"2) how much extra maintenance is needed with the addition of the rear shock? Will I or my LBS easily able to replace it when it wears down?"

I've have over-stressed the design limitations for close to ten years (note my posts) and the shock itself is still good.
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Old 02-18-21, 04:58 PM
  #2346  
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Originally Posted by mirfi
Lance,

I never had any issue rolling the 9FS around when folded, plus it had that super functional stand under the bottom bracket to keep the chainwheel off the ground.
But note, when I go shopping with it, I throw it in the cart (WallyWorld) or at the grocery store I leave it unfolded, just turn the handlebars 90 degrees, fold pedals and shop around until the basket is full.

As for
"2) how much extra maintenance is needed with the addition of the rear shock? Will I or my LBS easily able to replace it when it wears down?"

I've have over-stressed the design limitations for close to ten years (note my posts) and the shock itself is still good.
thanks i'm only 120lbs and don't ride that often so that's good to know!
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Old 03-10-21, 11:48 PM
  #2347  
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So I just got a Downtube 8H and the bike feels really high quality (haven't ridden it yet - by the time I got home from work, adjusted the brakes, swapped the saddle, etc. it was too late to ride). The latches are great (although my front wheel quick release lever is a bit scuffed up from shipping damage I assume). There's a minor annoyance that the seat post quick release doesn't stay in place when trying to tighten it, it'll freely rotate around if I'm not careful, but that doesn't seem like a big problem.

However, I'm a little disappointed with the fold so I'm wondering if I'm doing something wrong. It's not the size of the fold, and I like the latch mechanisms as already mentioned... but the bike just doesn't stand vertically on its two wheels when folded. Or at least I haven't been able to find a way to make that work. I have to lay it flat on its side, which means it doesn't fit where I need to store it in my apartment. Am I doing something wrong? Any suggestions from other owners? I've got a Dahon and a Tern that both are able to stand vertically (unless their wheels are flat, but I already filled the tires on the Downtube).

Also, the lack of any type of latch other than a strap of velcro to keep the bike folded seems to make it difficult to carry without it trying to unfold itself. Not a problem for putting it in my car, but it might be a problem when trying to carry up and down the stairs to my apartment every day. Again, maybe I just haven't found the best way to carry it yet. My other two folding bikes have a magnetic latch though and I never thought I'd miss that so much.
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Old 03-11-21, 09:08 AM
  #2348  
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Originally Posted by jhoff80
. . . the lack of any type of latch other than a strap of velcro to keep the bike folded seems to make it difficult to carry without it trying to unfold itself.
I've got a different folder (Giant Halfway), but the same problem. I keep a short bungee cord wrapped around the seatpost. I used it to hold the bike together when folded. Problem solved. For me, at least.
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Old 03-11-21, 05:50 PM
  #2349  
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Okay, we had one nice day before it gets freezing again, so I had to take advantage of it. I'll say it was a really great ride, and after 15 miles of city biking, I really like it as a bike. And it wasn't quite as bad as I feared going up and down the stairs. But the fold / inability to stand it vertically without tipping over is still a little annoying.

I will say it's a little odd to me though. I've been using a 2-speed Automatix with a coaster brake for the past 5-6 years. So having control over my gears was a little weird, and just some of the things I've gotten used to (like leaning back on the cranks as I slow down) as well as the front suspension which is new to me definitely had me feeling slightly off balance.

Crazy though how a bike that's cheaper than my previous one really does feel more high end though. Definitely a better hub, and the belt drive feels great, and even just the handlebars feel nicer too.

Last edited by jhoff80; 03-12-21 at 08:12 PM.
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Old 03-20-21, 11:57 PM
  #2350  
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Thank you for sharing
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