Large capacity aerodynamic tailboxes.

[Karl42]

Build it so you can mount it to the seat

As @Henri has found, a large box that is just attached to the seat is likely to be wobbly and unstable.
I think it would be good to have some support struts that rest on the lower frame or the rear axle, something like this rack from Tailfin:


Of course, if you are building something from scratch specifically for the V20, it could directly sit on the lower frame.

 

[Henri]

As I have a different seat mounted for it and the box is still mounted to the seat only top and middle, not in the lower part, I still have not judged that finally. I still have not taken it apart and looked at what was manufactured for me as a way to mount the seat to the frame and I have not looked into the source of the wobbling / wagging the tail. Might be that a stiffer mount of the seat and connection between box and seat would help and possible that the wobble partly comes from a loose headset or soft rear frame. Even my wheels could be a bit flexy in the sideways direction, I can not judge that. I had heard that certain FWD recumbents have very soft rears and it normally doesn't matter, but with much weight so far back it might matter; also compounding with all the other possible factors I listed. And if the rear fram is soft, supporting a box from it might bring it's own problems in that it further twists the box, seat and mounting hardware.

Also I said before, that with just a little getting-used-to I was able to ride without noticable wagging. It's probably a matter of resonance, so maybe I was just unlucky to create a noticable wobble at all. - I hope in the coming months I can finish personalizing my new-to-me home, get parking and maintenance in order and find time and energy to ride again and to inspect and tinker. - And to write a report and show off my very special build. XD

 

[vosadrian]

I would not connect anything that is directly connected to the headrest to anything on the lower frame. I tried to enclose that area on mine with some carbon sheet and had nothing but issue as the head rest flexes a lot relative to the lower frame as part of a suspension system that makes the bike more comfortable. The carbon sheet made lots of noise over bumps and flexed enough that it hit the wheel and ripped. I gave up and only enclosed the triangle.

 

[Frito Bandito]

Good points Adrian. My mock up was only connected to the bottom of the seat and some sections of the frame and stays, which was pretty much done to avoid it being a hassle to install or remove without having to deal with the head rest, not because of flexing, which is a "whew" moment for me. Somewhat intentional, I knew that if other V20 riders wanted to do something similar to what I eventually get around to, that it would be possible for them to do so regardless of which head rest bars they are using.

Now is as good a time as any to start on it I suppose.

 

[Henri]

There should still be limited potential to get some support from down there, but it would need to be designed in a way, that can flex with the frame as much as needed. To just carry some if the weight, that should be quite possible and make for a bit of suspension for the cargo.

I really prefer the thought of mounting the box to the seat over mounting to the head rest, when some weight will be carried. I think most available boxes I am aware of, are designed for that and run the length from the shoulders to the waist for that reason. Possibilities I see for that:
- Put them under the stock seat, but fill the gap, because these boxes are made for a different shape of seat. (Oh, I have a cruzbike seat and a less-aero Toxy box laying around, I should put then next to each other and make fotos for you lot?)
- Change the seat. (In Europe I can think of Thor, Novosport/Proceda/Toxy and maybe M5? USA does not seem to have much, if I mostly read of Thor in this Forum?)
- Build an own box fitting the Cruzbike seat.
- Build a way to attach the box to the frame; one that sits between frame and seat?
- Build own box and own seat, maybe as a unit. Could be some kind of split design, to rest firmly on the frame like the cruzbike seat and go around to enclose the cargo space. My mind is currently boiling with different ways to split it. I wish I had the time, patience, skills to build that. I really have to sleep now, if you are interested, ask me to try to remember and explain my ideas.

 

[LarryOz]

- Build own box and own seat, maybe as a unit. Could be some kind of split design, to rest firmly on the frame like the cruzbike seat and go around to enclose the cargo space.

This is what I meant by attaching any tailbox you get to the seat. Just put a couple bolts thru the seat on each side into the box - and it should be enough to hold it. If it is really big and heavy - sure you can put some rods from the rear-dropout back up the box.

 

[GetBent]

Neither sexy nor elegant, but functional. Good for light bulky items. Currently have a bladder in it. I use a long tube that goes to the right front of the underside of the seat, where the valve is held by a key retractor.

 

[Frito Bandito]

Looks nice GetBent. I saw 1 of those at my LBS (without the mounting bracket) and considered it for a really long time because not only is it a decent shape aerodynamically, but it is spacious (4L), the aluminum bar looked sturdy enough to handle a bit of weight (5kg) and the zippers seemed liked they wouldn't fail in a month like every other Topeak bag I've had.

That light you have looks pretty spiffy too.

 

[roadhog]

Hello,
I have made several tailboxes over the years. This is the fastest. It is made from expanded foam(neopolen) It is integrated with the seat mat and only supported by the seat. The top of the seat mat folds forward for access to luggage. Not the prettiest but really fast especially in sidewind

 

[Randyc3]

I use the performance adjustable headrest on my V20 so that big gap would likely be beneficial fit wise. How to connect the tailbox would be my concern though. By itself the tailbox weight is likely fine, but I'd be very careful about how much weight I put inside. Not so much for speed or balancing except on big crosswind days, but more so for the frame's weight limit and having the connectors fail. Just with the weight of my head, and I am sure the weight of all of my various tail bags or hydration attempts contributed to this also, but the weld on the top of the small backplate on my V20 failed. This is the one that has the holes for the head rest bars to pass through. It simply separated from the flat plate the seat connects to. This is why I feel hesitant to put a hydration bag or anything else heavy in my tail bag.

Hi, I’m curious. Can you post or send me a picture of the weld failure at your convenience? Was just imagineering how to make an M5 Tailbox for V20c if there is interest. Thanks.

 

[Frito Bandito]

You can't really see it from this angle, I'd have to remove the seat for that, but the hairline crack is right at the spot where the frame and CF seat comes together between the headrest bars. When I had my seat off I tried to squeeze it from several angles to see if it would widen with a bit of pressure, but the crack didn't widen at all.

 

[Randyc3]

You can't really see it from this angle, I'd have to remove the seat for that, but the hairline crack is right at the spot where the frame and CF seat comes together between the headrest bars. When I had my seat off I tried to squeeze it from several angles to see if it would widen with a bit of pressure, but the crack didn't widen at all.
View attachment 16737

Thanks!!

 

[BentAxel004]

Thanks!!

I have used the Cruzbike rear case, two of which failed. I am not an engineer, from what I experienced the cantilevered design, is the problem. When the rear wheel hits bumps, the case bounces and after a while the mounting fails. Any design must be cantilevered to mount to the head rest tubes. I’m considering rebuilding my aero case with an “L” bracket supporting the case. In essence the case would sit on the “L” bracket. The bracket would connect to the head rest tubes in the default manner. After two cases failed, it is clear that the lever weighted with what ever is in the case is flexing and the is what caused the failure. I don’t know what 2 water bottles weigh, but after the first failure I made sure I only used the holder closest to the bike. Still failed. The forces acting on these cases is not accounted for in the old design. I generally just ride on asphalt surfaces but these can be very bumpy.
I am wondering if any of the Cruzbike Aero box owner have come up with a time tested fix?

 

[Mathew Fy]

I shared this experience with Cruzbike's second version of their Race Case:

New race case?

Cruzbike just released a new video about attaching lights and mirrors to a v20... Shows a new design race case. Looks a little boxy, Matt black, more robust bidon holders, flag and light attachments.... But it's not up on the website....

forum.cruzbike.com

Prior to the revision to the one with the screws and stronger mounting plate, I had used a stronger attachment with a part of the "Headrest Cage Mount Kit".

One other thing that helped was a strip of handlebar tape between the case and the headrest bars, to smooth vibrations. I still had trouble with water bottles launching out of the holders when hitting a bump at speed. Very frustrating. Some people claimed wrapping some tape around the bottles provided enough restraint to prevent that, but I eventually abandoned the case.

As for the welded on cover of the hydro-formed frame, I think of it more of a dust cover. The real support for the headrest tubes comes from being held up by the clamps (scissor style vs. Perez style.) The Scissor clamps were a bit of a pain to use, but were very strong. The Cruzbike version of Jason's clamp work well, but have some potential to fail. Check that for potential loosening.

The photo below shows how the clamp is supported by a slim area of aluminum. That's a big ask.

 

[Randyc3]

I have used the Cruzbike rear case, two of which failed. I am not an engineer, from what I experienced the cantilevered design, is the problem. When the rear wheel hits bumps, the case bounces and after a while the mounting fails. Any design must be cantilevered to mount to the head rest tubes. I’m considering rebuilding my aero case with an “L” bracket supporting the case. In essence the case would sit on the “L” bracket. The bracket would connect to the head rest tubes in the default manner. After two cases failed, it is clear that the lever weighted with what ever is in the case is flexing and the is what caused the failure. I don’t know what 2 water bottles weigh, but after the first failure I made sure I only used the holder closest to the bike. Still failed. The forces acting on these cases is not accounted for in the old design. I generally just ride on asphalt surfaces but these can be very bumpy.
I am wondering if any of the Cruzbike Aero box owner have come up with a time tested fix?

Hi, what… bumpy roads? Previous to designing a tailbox I had tried the headrest mounted water bottle holder which always slipped no matter what fix i tried. My conclusion was clamping force cannot stop slippage due do riding on bumpy roads(only road type in my area).
The design approach:
-holder to match headrest tubes
-bracket or some type of structure from top of headrest tube to prevent slipping of Tailbox down tubes.
Design-
Made a 3d printed bracket matching the tubes. Use 1 cross bracket(white piece-prototype)to hold the tailbox to the headrest . Currently using a small SS cable wrapped around top of head rest tube and connected this via 200lb D link to prevent slippage. Not aesthetically pleasing but is working so far. Haven’t noticed any slipping.
Fyi- density of water is 8.3lb/gal for your water bottle question.
Comment- I do share FritoBandito’s concern about adding alot of weight/carrying capacity.
Other ideas:
-cut headrest tubes and weld flat plate as a mounting bracket for a tailbox(only good for V20c with new seat)
-replace headrest tubes with composite tubes and integrate with composite tailbox(same as previous unless you make headrest provisions needed for old V20c seat). Hope this helps or may give you some ideas.

 

[vosadrian]

I have some photos of my mount here: https://forum.cruzbike.com/threads/adrians-v20-tail-box.14393/

It has been very strong and durable. I did it this way to support the weight of the box from underneath it to prevent bolts in carbon from cracking and failing.

Just reposting the above. If you follow the link above, you will see my tailbox mounting system. It uses some 19mm hose seperator clamps to clamp very close to the bottom of the headrest tubes. It then has some horizontal aluminium tubes that go from that to support the tail box from underneath. It has worked well so far with about 7-8000kms use on bumpy roads etc. Never moves and no failures.

 

[Randyc3]

Hi, have a few more weeks of work on TB prototype #3. Surface is bit smoother, but still needs some improvement(prototype #4?). Added 3d printed NACA 0010 airfoils for high speed descent stabilization and make the box “aero” so I could post.

 

[Henri]

Those wings look like some Animé space ship.

 

[Randyc3]

Idea came from the Beechcraft Bonanza and V tail sailplanes. Now thinking I will move these to the top of the TB and adjust them to be more vertical.

 

[Flying Dutchman]

Now the Vendettas can compete with the latest MotoGP bikes