erileykc

My poor choice in buying a cheap Chinese Rad bike in a box has come back to bite me. The top of the seat tube cracked off at the frame welds. Rad bikes has no frames and no interest in having anything to do with an 18 month old bike with a bad frame.

Best suggestion I''ve had so far for a repair is to drop a new piece of aluminum tubing into the old seat tube, welding that on to the old tube along with the broken piece and installing a new, smaller diameter seat post that fits the new, smaller tube. I'm told that this requires 'tig' welding. Can anyone confirm that is the right type of welding for this job? Does anyone know of a shop in the DC area that can tig weld aluminum?

Thanks for any suggestions on welders or different approaches to making this bike rideable again. Moral of the story is support your Local Bike Shop.

Also, if you come across an ad for Rad Power bikes in your feed I recommend that you just scroll on past.

squirtdad

I would ask in the framebuilders forum, but my guess is that the response is the frame is toast. if the weld failed in a low stress area (unless you were using 1 inch of seat tube) what are the chances of other welds failing?

dsbrantjr

Bin it, I would never trust that frame. What makes you think that any of the other welds (or the tubing for that matter) on the frame are reliable? Besides, even if you had the frame repaired it would need heat-treating after welding. This is unlikely to be economical even if you cold find someone to do it.

freeranger

As dsbrantjr said, if one part of the frame cracked, other sections may follow. I'd be looking for a used frame on Craigslist, or wherever, to transfer parts to.

grizzly59

Aluminum frames are welded then heat treated. You need the proper heat treatment which a good tig welder can't do himself. Frame is scrap. New frame is far far cheaper than your medical bills when the frame discombobulates on a downhill curve going 30mph with oncoming traffic. Sorry for your loss.

alo

I suggest buying a new bike. One with a stronger frame. If you buy the same size bike, you have a full set of spares, of everything other than the frame.

Don't spend money on a frame which may fail somewhere else.

delbiker1 

Accept that you made a poor choice and trash the piece of junk. Learn from the mistake and it was not a total waste.

CliffordK

How did you manage to break the mast where you did?

Rider Weight?

How much post extends into the frame? Did you use the "minimum insertion" mark? Perhaps with a mast, one should have the minimum insertion point below the top of the top tube (or at least 2" into the frame).

Is the seat tube round below the seat stays?

What diameter of seatpost do you have?

If you had a quill post like the 27.2 posts from the 80's or 90's, then you could just clean up the top of your tube, stick in the quill... give the finger to those saying to trash the frame... and keep riding.



Unfortunately there are few options available. Most are short, and almost all are 27.2. However, in theory, you might be able to make a suitable quill.

dedhed

Toast.
Visit one of the DC area coops and buy a used frame compatible with your components and switch them over or pay the coop to do it.

https://www.google.com/search?q=wash...hrome&ie=UTF-8

3alarmer 

.
...I think a lot of the responses so far don't understand this is an electric bicycle, and looking for a new frame to swap components is a non-starter.

TIG and MIG welding are the accepted commonly available ways to join aluminum tubing, like this appears to be. There is an inert gas shielding that flows constantly around the area being welded with the bead of welding rod. The failure looks like the classic one you get from not having enough seat post down inside the seat tube. Only you know for certain if this was the cause.

I am entirely uncertain if your particular frame was heat treated as part of the construction process, but just looking at the thickness of the aluminum tubing walls in your photo, I would guess it probably was not. YOu could probably confirm that with the maker, which AFAIK is still in business. If that is, indeed, the case, It's a relatively simple job to re-weld that aluminum top piece back (sans the clamp) onto where it broke off (it won't look as pretty as it did new). A more professional repair would be to manufacture a new top piece from similar size and wall thickness tubing, grind off the remains of the old one at the break at an angle, and weld on the new piece using a fillet weld all around. (This is difficult to describe in words, but any experienced welder will know what I'm talking about.) Use some kind of internal tubing like an old scrap seat post or other pipe to make sure the thing goes on straight. It has to be slotted at the top, like the old piece, and the old post clamp needs to fit on it.

If you do go this route, in the future, make certain you have a few inches of seat post down in past the seat tube junction, to prevent a recurrence. This is probably especially important on an electrik moped styled bike, where the rider has a tendency to ride over bumps and potholes with most of your body weight on the saddle.

If you do find out the frame is heat treated aluminum, don't waste any more money on it. Consider this a life lesson on seat post insertion depth.

Bill Kapaun

Seeing how "cleanly" it broke near the toe of the weld (on the upper side) I'd consider this to be a lack of needed heat treatment after welding.

Maybe you'd have at least a taste of revenge by reporting an unsafe product to-
https://www.cpsc.gov/

Crankycrank

I'd like to hear a little more info such as how far the seatpost was inserted and how much does the OP weigh before trashing the mfr. Not taking any sides, manufacturing farts happen. Where I live I see plenty of RAD E bikes and have never heard of any frame failures and thinking of getting one for a relative so I want to know if this frame is likely to break or possibly user error.

3alarmer 

...I've seen a number of similar failures on homeless bikes here, where someone is riding with little or no seat post below the top tube intersection.
Not all aluminum frames get heat treated, and Rad power is not going for a lightweight frame. They're more putting out 50-60 pound fatter tyre e-bikes on the moped model.

I only know this because the guys across the street from me bought two of them last year. So far they seem to like them.

erileykc

The seat post was about three inches short of the limit mark screened on to the post. I'm 6'3 and weigh weigh 200 lbs. Whats significant to me is that I've owned eight bikes in the last forty years, still own four them and all were fitted to my size and weight. The bikes range from a 1979 Raleigh Tourist to a cheap Chinese Citizen folder. None of those bikes has had their seat tube fail. Without having a background in strength of materials engineering that's my basis for thinking that this is a problem with the Rad bike frame. I'm sure I'm an outlier on their product failures but I'm also sure that their saying tough luck to someone with an 18 month old bike with 1600 miles on it with a catastrophic failure ending the usability of the bike is not confidence inspiring customer service.

WizardOfBoz

As youve read above:

1) Aluminum frames must be made of good quality alloy and be properly welded and heat treated to be strong and useful.
2) The fact that your frame broke indicates that it either not quality allow, not properly welded, and/or not properly heat treated.
3) You could weld the frame, but if the alloy is poor, it will break again.
4) You could weld the frame, but you'd have to heat treat it and this would require refinishing it.

There are no safe, low cost options for repair. Saw the top tube with a hacksaw (to prevent the great unwashed from trying to fix it and creating an unsafe situation) and buy a new frame.

alo

Good idea.

If you want to keep using the bike, and are creative, make up something like this, but longer. Just grind off the jagged edges where the frame is broken, but don't bother welding to it.

Koyote

This is terrible advice. The OP states that he had the seatpost inserted plenty far enough and did not otherwise abuse the bike, and it still failed catastrophically. The frame is not safe.

CliffordK

Is this the bike, or similar?
https://www.radpowerbikes.com/produc...-commuter-bike

18 months, 1600 miles is well outside of what one would expect for failures. There are quite a few road bikes that are still on the road at 50K to 100K miles, or perhaps even more.

Weight sounds fine... but 6'3" on a "one-size-fits-all" bike with an 18.5" frame? Their website lists:But, to me, that is optimistic.
It also lists:Did you install a longer post? You must be awfully close to the 35cm length.

27.2 is standard for yesteryear, but I would expect 31.8 to 35mm, especially with the one-size-fits-all and sloping top tube.

Is it possible your seatpost is undersized? 27.0? Putting undue stress on the mast as well as not fitting the seat tube well?

erileykc

This is the current version yes. I don't have documentation of the geometry for my 2018 bike. When I bought Rad offered a small and large frame and mine is the large version. I have no idea how that relates to what is now, as you say, a one size fits all bike.

Andrew R Stewart 

If we could see an edge on photo of both parts, showing the fracture face we might be able to give stronger opinion as to the failure mode. This whole situation, from the less then ideal sizing/fit, the broken frame and the lack of any support from the seller/manufacturer seems like a series of choices, all less then stellar in hindsight. Andy

CliffordK

Personally I would try butt-welding it. I struggle with aluminum welding, but a good welding shop should be able to do it for you. I'd ask about local machine shops that do aluminum, and not necessarily bike specific shops.

Ream the over-penetration and ride. Make sure the the seat post is reasonably tight, and long enough.

It does look like the front side of the mast may be damaged slightly, so perhaps clean the lower portion, then weld on an all-new upper portion of the mast. That would also allow you to slot it independent of the new weld.

According to the specs:That is one of the most common types of structural aluminum, and should be easy to replace, and easy to weld (for a good welder).

A lot of people don't like welding onto an existing bead, although it was the tube and not the weld bead that failed.

CliffordK

Do you have a photo of the bike configured like you were riding it?

Measure the seat tube from the middle of the bottom bracket to... I like to measure to the top of the top tube. But, some might measure to the top of the mast.

Like I said, start hunting for a good local welding shop that does aluminum. But, you could end up paying a couple hundred bucks for the repair, and it won't necessarily blend the paint perfectly. But, it could get you back on the road.

I can't say if it would be stronger or weaker than the original, or if other faults would eventually show up. With a long enough seat post, the mast failing like it did should be uncomfortable, but shouldn't cause a crash.

Obviously other failures like a dual headtube failure could be far more dangerous.

3alarmer 

Quote:

The best support in the industry.

...this is right off their web page.

I went there looking for any information about their frames and the construction of them.
All I could find was some references to 6061 aluminum as the current frame material. That seems to be the case for all the different models I checked.

The stuff gets used for a lot of different applications (as you can see if you read the link), and it's not always heat treated for additional strength, because with a thick enough wall size and some time at rest, it regains quite a bit of the strength lost in welding from the heat. In your case, there was obviously a lot of heat at the point of failure during construction, but I still don't get why it would break off right there with a properly sized seat post fitted in there, and inserted at least three or four inches below the bottom of the top tube/seat tube interface. So I don't have any real good answer, and i know it must have set you back maybe $1500.

They (Rad Power) advertise like there's no tomorrow (around here in NorCal anyway). So If I were you I think I'd try one more time to contact them, mention the Consumer Product Safety Commission report I intended to file requesting their product be recalled, and see what happens. As you have already stated, 18 months, 1600 miles is not much usage.

But I have to warn you that when they look at your frame, they're gonna say you didn't have the seat post inserted in far enough, and blame that as the reason for failure. That's what I thought, just looking at it, and I think most people who have seen similar failures will concur. But maybe they'll do something on your behalf just to shut you up if you go all CPSC recall on them.

CliffordK

How was the "Minimum Insertion" developed? It is obvious why one has it... but, is there any science behind it.



For the vintage steel, I'd insert the post to an inch or two below the top tube.

Likewise, on the "Rad" bike above right, I'd still insert it to an inch or two below the top tube. But, with the 1" to 2" high mast, that would put the insertion point an inch or two lower.

Plus, of course, using different frame materials.

The other thing that happened since companies started specifying a minimum insertion point is that seatposts have grown much longer. So, standards for an 8 to 10" seatpost may not apply to a 12 to 20" seatpost.

I realize the reason for using the mast is to simplify the locking mechanism and use the band clamp. But, it may also necessarily change how the frame reacts to the seatpost.

cpach

With your (not exceptional or crazy) height and weight and the higher average speeds of an eBike I could not in good conscience recommend any repair to that frame. It is a death trap.

Welding of that frame will not be as strong as it should be because aluminum frames are supposed to be heat treated post weld, and pretty much noone is going to sign up to completely dismantle that bike, tig weld the seat tube together, throw it an oven for a couple hours at 800-1000F, repaint the frame, and reassemble the bike for less than the cost of a not-terrible ebike new.

If I had a death wish and too much time I'd probably file down the broken seat tube, sand the inside of the seat tube clean, JB weld a 27.2 post in with a ID of <22.2mm, ream it to 22.2mm, and use a 22.2mm post.

As it's a hub drive ebike, I think the only real ebike specific feature of the frame is the mounts for the battery. You could probably install the eBike components on another bike frame if you fabricated a battery mount onto a sturdy rear rack.