United Trifold: Frame and Hub Issues

While building the United Trifold in the previous posts, I keep writing about how the frame is not straight. For example, the rear triangle itself is a bit twisted, as the left and right side chain stays are not parallel. The axis of the bottom bracket and the axis of the rear axle are also not parallel, which I found when installing the crankset and aligning the chain line.

Those are not so obvious, and can probably be spotted only because removed the components from the frame. That said, I can't feel any issue when riding the bike, despite having these misalignments.

Other than those, there are also other areas where there are frame misalignments, as you can see below.

Handlepost is not parallel to seat post.

These two "posts" should be parallel, which is a basic requirement.

Unfortunately, this difference is quite obvious, and can be felt when riding. This is similar to the problem that I faced when building the Fnhon DB11 folding bike.

It seems that the problem is from the United Trifold frame, not the handlepost, as the tilting is still present after I swapped to the new Fnhon handlepost. The head tube is not parallel to the seat tube, which is another problem with the manufacturing of the frame. There is also no proper QC which will detect all these issues.

Front fork is also not straight. Wheel is tilted and offset to one side.

There is also an issue with the front fork, where the front wheel is not nicely centered within the dropouts. It seems that the fork legs are not aligned, causing the wheel to tilt to one side. However, this problem cannot be felt when cycling.

I am not sure if I got a lemon frame, or are the QC of all the United Trifold frame like that. You can check your own to see how it is.

When I modified the drivetrain to become a single speed drivetrain, it is with a normal freehub rear wheel. For normal riding there is no issue, but when I am pedaling up slopes, and I stand up to pedal, there is sometimes a loud cracking sound coming from the rear hub area. This only happens when I apply high torque to the pedals.

There are a few possibilities for this to happen, which I checked thoroughly.

1) Chain slips over the sprocket teeth, due to insufficient engagement. This is not the case, as the sprocket teeth are tall and prevent the chain from skipping.

2) Sprocket splines skips over the freehub body splines. Upon checking, this also did not happen. There would be very obvious marks on the aluminium freehub body if it did happen.

3) Pawl slips from the ratchet, at the pawl and ratchet mechanism inside the freehub body. I opened up the rear hub to see if I could spot anything.

Freehub body removed from the rear hub. This structure is somewhat similar to the Wheelsport rear wheel.

There are 3 pawls instead of 6, which means more chance of skipping. However, I did not spot any damage at the tip of the pawls.

Also no damage on the ratchet, all the teeth look perfectly fine.

In the end I could not find the source of the cracking during high load, but I was also glad that no damage was done. If there are slopes I just have to make sure that I do not apply too much torque.

If I had paid a premium price for the United Trifold, I would be really unhappy with the frame problems that I found. However, since I got the bike at a good deal, I can accept the defects. I wonder if the Brompton clones such as the 3Sixty or the Pikes have similar problems or not.