QX100: upper seat broken: missing seat support? welding possible?

[veloc_h]

Hi there
Yesterday I've just bought a second hand QX100 and I love it! Today I realized that there are two cracks (green arrows) at the upper seat (very close to the two screws, which connect the upper and the lower part).
Just wonder if there is one support missing... There are five free wholes in the lower part of the upper seat (red arrows). Could it be, that one support is missing? Might be the reason for the two cracks: too much force onto the area around the two screws especially if the seat is a bit bended (the seller's sun had fallen off the QX100...).

Has anybody welded a cruzbike seat? Apart from the fact, that the welding of alloy is difficult, there is a gap around the cracks, so the seat should be pressed together before welding. And it might have to be reinforced at these places after welding (with the help of a bended slim rectangular alloy profile may be?).

Best regards
veloc_h

 

[veloc_h]

edit: just had a look at the youtube qx100 mounting video: obviously there is no second mounting bracket

 

[benphyr]

edit: just had a look at the youtube qx100 mounting video: obviously there is no second mounting bracket

Correct: there is only one mounting bracket on the seat post.

The two red arrows on the left rear of the seat back are for mounting a bottle cage (or similar) to the seat back and should not affect strength of the seat. I cannot tell what the other red arrows are pointing at from the picture but I think I have them for bottle cages on right and left and assume d the central one could be used for mounting something else to the seat back (bag, headrest, or ?)

Those cracks look pretty significant. I would suggest replacing the seat at your earliest convenience. (Mine has cracks that I noticed a thousand km ago see below for what they look like now. but I am light (61kg) and easy on equipment, and miserly and tend to be really good at telling the difference between damaged and can limp on vs. failing and avoid use.) But I cannot recommend myself. I’m a bad example.

 

[benphyr]

I see you have already posted in the marketplace to buy a replacement seat back. There are several who have upgraded their seats so there are probably some available. Some even tgat are brand new. If you get one of those you might want to get the seat bottom so you have a full one without wear. Not sure of any in your area though.

Alternatively, Thor seats is much closer to you than to us in North America. You would have to do some mount fabrication but it would be a significant upgrade by all reports.
http://www.thorseat.eu/en/thor-composite-recumbent-seats/

 

[DavidJL]

I had trouble with cracking at the screw holes where the two parts join. I ended up cutting off the bad parts and joining the seat together with aluminum strips. Pic shows T50, but it was the QX100 that had the seat cracks.

 

[veloc_h]

I ended up cutting off the bad parts and joining the seat together with aluminum strips.

Thanks for sharing your experience. It's a constructive weakness in my point of view: the weight of back and shoulders should be transfered directly by two support to the frame. The upper support is not sufficient. It's called tension crack (tension is caused allready by the manufacturing process of the alloy shells: deep drawing).
I wondered to insert an alloy strip close to the cracks from left to right, connected by pop rivets. Like that the cracks should be reducted. After that I would either hard solder the cracks (or glue the cracks or use metalic modeling clay, which I have seen some days ago at the Jumbo market) and to reduce the tension by attaching triangular small alloy-profile to fit my seat angle exactly. I would use the triangular alloy profile even with a plate, which might be offered by a nice forum collegue. Must talk to my mechanics friends (unfortunately they work in other areas like clock work repair).
What I do like a lot with this constuction: the possibility to adjust vertical angle and position of the lower "pan" independantly.

Thor seats is much closer to you

thanks a lot for your recommendations.
actually there is quite a lot of choice in Europe: the seats from e.g. azub.eu, hpvelotechnik.com (German), or recumbentparts.com (in the Netherlands) ICE and novosport.de are good ones as well. But customs and transport to Switzerland are expansive!
On my Bacchetta CA3 I have a carbon seat with ventisit, which I like (apart from sweating). Because of sweating I prefer grid-seats like the one of my Swiss Wolf&Wolf Alpentourer alpha FOS license, which is integrated to the frame (no possiblity to adjust seat position or angle!). But at the present I'm eager to drive the Cruzbike as soon as possible so I would prefer to postpone the installation of a 3rd party seat (tricky mounting...). I have also asked Cruzbike how much a new seat from the US would be and have sent emails to the European sellers if they have a seat on stock.
Apologizes for my bad English: I'm not a native speaker.

Those cracks look pretty significant. I would suggest replacing the seat at your earliest convenience.

I totally agree: one of the screws of the lower "pan" can not be unscrewed. Still waiting for the effect of the Swiss weapon oil "Neoval"... so that I can show the "pan" to my mechanics friend.

 

[benphyr]

Note also the top bracket in my photo above. Your has definitely taken a beating and is out of alignment/adjustment for sure; possibly bent.

Note: I take full responsibility for my seatback crack. I tried to cold bend it so I could get below 40 degrees seat back angle with my favourite seat bottom angle/location and rode it with loose attachment bolts and commute with my bag hooked over the top of the seat back. The first two almost certainly contributed to the cracks.

 

[Rampa]

If you trim off the folded ends with the screw holes, you could join the upper and lower parts with a short piano hinge. That would not only be strong, but articulate easily for adjustment.

 

[benphyr]

The fold should also give some structural strength. That is, before they cracked they should have.

 

[veloc_h]

The seller's son fell to the right (scratches on the luggage carrier).
Cold bending is no good with alloy (says one of my professional mechanics friends). Allways with heat (hot dryer). Otherwise you get hair cracks. And even then it's tricky with alloy.
Actually the top bracket doesn't look that bad in my point of view. But you are right in advising to be careful: I should show the bracket to my mechanics friend. Is there a more recent and more solid bracket available? I haven't seen a listing of cruzbike spare-parts nor a shop.
Regarding the Qx100/Q45/T50 seat: it's deep cold pressed: causes a lot of tensions which should be released by heat after the pressing process. Otherwise a smal crack (caused by falling or corrosion) gets big instantly.
Plus the force flow to the upper seat and then to the frame by two thin screws... Force of the body towards the ground must be spread as even as possible. @Rampa: I do like the idea of the piano hinge, thanks. May be a stronger version like this one: https://www.hornbach.ch/shop/Scharn...MI5Le5u6iC8QIVTZ_VCh21fgV1EAQYBSABEgKDRfD_BwEI have been offered a wooden seat by a friend, unfortunately no longer produced by Velomo: http://www.velomo.eu/bikeparts/hibone. In combination with a ventisit mat, it's a a sweating free and light solution. The seating angle might be too flat. I'm going to test it today.

 

[benphyr]

Have you contacted @Robert Holler or support@cruzbike.com? There are only accessories for current models on the website but they sometimes have parts for older models or repair parts that are not listed available.

 

[veloc_h]

Yes, I did and they reacted instantly and were very helpful (it takes some time to calculate customs, vat (?) and transport to Europe), but I'm surprised, that there is no pdf with spare-parts and their material numbers. I have also contacted the French distributors (I live in Switzerland, but there is no distributor in Switzerland and in Germany) whether or not they have a QX100 seat on stock.

 

[veloc_h]

A friend of mine told me yesterday, that he doesn't need his Velomo wooden seat any longer.
The photos show a simulation (brackets are missing, so I must wait until tomorrow) with this seat, size Large. Because my back isn't that long, I could use the most upper part as a headrest). Weight of the seat is 1kg. Much more reclined than the original Cruzbike seat (the angle of the Velomo seat is about 38 degrees). I would have to cut the upper steering tube because the view would go to the handle bars.
Does the QX100 demand a steeper seat or does it mean only, that the beginning is more difficult? I might be able to change the angle a very little bit, may be 3-5 degrees. The seat is used, that's why the colour is gone partially. The beech sticks are impregnated, As a result the black colour didn't stick. The cheeks are made of pine tree.
I wonder whether or not I should try to get size M (M and L are the two available sizes), but I have doubts that my head would bang against the upper part of the seat (at the present it's ok with the helmet on). This wooden seat is not available in the Thor seat easy mode... it seems that the line of the Velomo seat corresponds more to the Thor sports version. I might use a Ventisit mat on it (must check, whether the old mat, I have got, would fit...).

 

[veloc_h]

sorry abut the triple post, but I can't edit any longer...
Did the test now with a bicycle helmet, different positions and different angles: because the seat is quite big for the size of my back, the last three upper sticks push my cervical spine; with an angle of 25 degrees it works. But can I ride the QX100 with this angle? Don't want to drill too many wholes into the wood...

 

[benphyr]

My QX100 is at about 37 degrees.

 

[veloc_h]

Thanks a lot, @benphyr! I really appreciate your help. Just had a look at the Q50 seat doc (https://cdn.shopify.com/s/files/1/0...ly-T50-Seat-Assembly.pdf?13834520716469322793) plus the Q45 video:

. Totally different from my mounting system.
By the way: I'm not the only one whose seat is broken:
https://forum.cruzbike.com/threads/quest-bike-seat-broke-this-morning-replacement.4257/
https://forum.cruzbike.com/threads/did-you-cut-your-quest-seat-pan.8772/
https://forum.cruzbike.com/threads/cracked-seat-back-on-early-quest.11756/
Yes, these tension cracks are a typical material science problem (and how to avoid it: for example by avoiding wholes or sharp edges at the places of high tension during the construction process; or by spreading the force (a set of washers, as shown on the Thor side helps)

 

[veloc_h]

These is my "bracket" for the seat-pan: apart from the supports it's the only bracket. More recent frames do have two quick-release brackets.

 

[veloc_h]

Is the bracket system typical for the QX100 (two screws plus two supports for the lower part)?

 

[jond]

@veloc_h if you look up on Facebook the group ozhpv recumbent for sale swap there is a seat of the right colour for $50 at Coffs Harbour. Unfortunately that’s Australia but they may post. Listed couple days only.

 

[benphyr]

Yes, it came with thumb screws for easy, tool-free disassembly for travel / fit in vehicle. This is how mine is assembled in sequence from top down pan head hex screw, seat pan, washer locknut, support slot, washer, thumb screw nut / wing nut. It is likely incorrect and could be the cause of my seat cracks. The seat pan flops around a fair bit. Someone once advised me that their Quest did too through many long tours so I didn’t think anything of it. @Robert Holler can probably advise the correct sequence.