Midrack - this is how it is done

[JonB]

Hi

I have made a midrack under the seat for my Cruzbike Freerider. Pictures will follow when tomorrow when it is daylight. I spent untold hours talking and thinking about how to make it. I made and mounted the first prototype in 4 hours and 15 minutes. I wasted at least 2 hours making stuff that didnt work in reality.

In the end what worked was a rear triangle made of 3 pieces attached to the tube clamp and a spacer piece between the 2 arms from the tube clamp. All 3 pieces form the rear triangle. 2 arms in front attached to the most forward seat bolt in each side.

The 2 front arms and 2 rear arms are wrapped arround a solid 10 mm round aluminium piece which is bent and shaped like a U. To keep the wrappings secure i have bolted them together with 2 cm extra wrap arround the round solid.

To make the 4 arms i used 2 cm wide, 2 mm thick 20 cm long aluminium which i wrapped arround the solid round 10 mm. The spacer piece is 16? cm of the same 2 cm wide 2 mm thick aluminium.

The luggage carrier part is a 100 cm long 10 mm thick round solid aluminium piece. I only made it 100 cm, bent arround the middle, about 10 cm used for the rounding, meaning 45 cm for each side for panniers. This piece could possibly be 10-15 cm longer on each side further extending the rack onto the sides of the rear wheel.

 

[JonB]

Today was my first real usage of the midrack, yesterday i was driving home with an empty pannier. Today it was LOADED. 2 17" laptops, 2 PSU's 1 extra mouse, 1 extra battery, some cables and thin rain clothes. In the beginning i was noticing that the bike had a strong tendensy to tip to the left, where the pannier was mounted, but after 20 minutes of riding i forgot it, and i would guess i relearned how to keep the balance.

I find the midrack very usefull and i hereby place my design under public domain so everyone is allowed to copy and do further development based on my design ideas. I especially hope John and Jim will make it an option to the official cruzbikes because i think it increases the usefullness of the bike.

I will now post the pictures, first some where it is loaded and then some where you can actually see the design.

 

[JonB]

Here are the pictures with a 17" Altura Urban Laptop pannier. It does look like the straps hit the ground, but there are plenty of space.

 

[JonB]

Now for pictures of the empty rack, so you can see the design.

 

[JonB]

And finally better pictures of the front holder attached to the seat.

 

[Mark B]

Nicely done!

Mark

 

[Peder Torgersen]

Did you use stainless steel? It looks very good and practical.

Peder

 

[JonB]

Peder Torgersen wrote: Did you use stainless steel? It looks very good and practical.

Only for the bolts, nuts and washers. All the other material is aluminium.

 

[Mark B]

Jon,

I have a question. How does your bag attach to the aluminum rod? Many panniers just have two hooks on top that hang on the rail, then have a hook on an elastic strap on the bottom. The hook and elastic strap arrrangement is to keep the pannier from jumping off the rack when you hit a bump. Therefore, most pannier racks are triangulated, to some degree, or have a hook of some sort on the bottom to attach your pannier to. So, unless your bag attaches firmly to the rod, I would caution you they can jump off pretty easily!

Maybe the nxt evolution of your design? The triangulation would be very easily done with your design; just another rod bent into a v and welded to the main rod. As long as you're welding, you just as well weld the strap and do away with some bolts.

Mark

 

[Gromit]

Supplementary questions Jon, following on from Mark's.
Does the bag move much on bends? Swing out to left?
Do you have another similar bag? Firstly to centralise the load and secondly so that you could tie the two bags together. The tie could also assist by helping to hold the bags down onto the midrack rails (Mark's point) by passing through the redundant bottom bracket tube in the Cruzbike's frame.

 

[JonB]

Mark B wrote: Jon,

I have a question. How does your bag attach to the aluminum rod? Many panniers just have two hooks on top that hang on the rail, then have a hook on an elastic strap on the bottom. The hook and elastic strap arrrangement is to keep the pannier from jumping off the rack when you hit a bump. Therefore, most pannier racks are triangulated, to some degree, or have a hook of some sort on the bottom to attach your pannier to. So, unless your bag attaches firmly to the rod, I would caution you they can jump off pretty easily!

I have attached a picture of the backside of my Altura Laptop Pannier. There are some small lock triangles that is operated by the big red button. This keeps the pannier locked to the midrack rod. I have ridden with it almost empty and FULLY loaded. I do not remember any flapping, jumping, swinging or anything, not even in turns. But i was also only driving on asphalt bike paths, and i was tired the day it was emptyish. Sure there was some minor road bumps, but i didnt notice any problems. The rear rack and/or basket was making more noises.

Mark B wrote: Maybe the nxt evolution of your design? The triangulation would be very easily done with your design; just another rod bent into a v and welded to the main rod. As long as you're welding, you just as well weld the strap and do away with some bolts.

Mark

I am not sure i understand what it is you want to do? Maybe it is the pannier, maybe it is the road, maybe it is the rack which is 3 cm out from the frame under the seat, but then the bag just hangs against the side of the frame in the bottom. I do not feel the need for something to hold the bottom of this pannier attached. Welding in aluminium is pretty toxic, and i cant even weld in iron. Or rather, i have never tried.

I do not think i want to do more with the rack, as i believe it works fine. But hey, let me test it for a few weeks and with some other bags, which i have yet to buy, but i plan to, since i might be bicycling to my parents this thursday since it is a holiday, so i take an extended weekend. If i wanted to hold the bags together i would probably go for a elastomer with a hook in both ends, to avoid the extra weight when i am not using it. ( i'm turning into a weight weenie )

I used 4 hours and 15 minutes to make and mount what you see. I was at least wasting 2 hours creating things i would not use anyway. Or things that broke. Or was too small. The material cost was something like $15. I believe that you can copy my design and mount it in 1 hour.

 

[Gromit]

Rixen & Kaul Klickfix Pannier Rails. I have those on my Altura panniers too. I find them very secure.

 

[JonB]

Gromit wrote: Rixen & Kaul Klickfix Pannier Rails. I have those on my Altura panniers too. I find them very secure.

My pannier came with the mount you see on the pannier picture seen above. But i must say it looks almost like what you found, i dont have the handle bar. I did move it from a 45 degree angle to horizontal and centralized.



I have now thought of one further development i may do, but i am unsure how well it will hold up. The development is to split all the 5 arms into 2 pieces which are bolted together. Possibly with finger bolts. The reason is that this could make it much easier to adjust the length of the arm and thus the height of the midrack rod.

Imagine long rectangles. Drill holes into them with a common distance. Then you can put bolts through at least 2 of these holes and attach the 2 pieces into one piece. Naturally the holes should come with a common distance, so you can in one piece use holes 1 and 3, and in the other you can use hole 2 and 4, or 1 and 3, or 3 and 5, or ...

But i dont need this, because i made the distance to fit my Altura laptop pannier, so it could fit under the seat. Other panniers where the hooks sit higher at the top of the pannier may want to move the midrack rod upwards so they can fit their panniers.



Another possibility i have thought of is a hollow cube made of 3x3 cm aluminium 1 cm wide. One side has 3 holes, top, mid and bottom to adjust the height. This is attached to one of the frame holes under the seat. On the opposite cube side the midrack rod is attached using something like U with wings. Or one can use an eye bolt instead of the 3x3 cm cube and stick the midrack rod through the eye.

But, the force is downwards, which would put strain on the frame or the cube. With my existing design the arm hangs down vertically. Sure the arm is bent at the top to be able to use the seat bolt, but that doesnt matter, because this will mean that what breaks is the midrack arm, not the frame.

 

[Gromit]

Just remembered seeing this carrier system on an HP Velotechnik Streetmachine.

Does the above give you any inspiration Jon?

 

[Mark B]

Gromit wrote: Just remembered seeing this carrier system on an HP Velotechnik Streetmachine.

[attachment]smgte_frei_links_total_oran.jpg[/IMG]
Does the above give you any inspiration Jon?

Jon,

The picture above is more or less what I'm talking about.... It does appear that the attachment on your particular pannier is sufficient, possibly no need for the lower attachment.

Mark

 

[JonB]

I see what you mean. I think part of the reason why they need something in the bottom is because their rack is so small. Mine is much wider, and mine is made such that if the pannier moves forward or backward it will not fall off because of the U which is closed with a spacer arm in the other end.

I also think that the bottom arms on the rack over the rear wheel is to prevent the pannier from hitting the wheel. Mine will never hit the wheel because there are no wheel where i hang it.

 

[JonB]

Updated experiences from using it.

I have once had the pannier slide forward, so long forward that it hit the wheel making turns impossible. Will make some stop thing.

I have bought an Ortlieb Back Roller Plus Panniers, and they fit my midrack just fine. They dont hit the ground. I also tried mounting 2 front panniers from Ortlieb, but the rod that the panniers hang on was not long enough. They hit the front wheel. So, if you copy my design and want the possibility of 2 front panniers, then you need to use a 120 cm rod and not just 100 cm like me. This will extend both sides with 10 cm which should be enough. To mount 2 rear panniers, you probably need arround 10 cm too, maybe 15. I dont know, and i no longer have a pair of back rollers since i sold one of the pair i bought (why is it they force you to buy a pair?)

 

[JonB]

Here is a report from my first touring test of the midrack. It still works fine and i see no need for having arms extended down from the carrier rod. It works fine just having them to rest against the frame of the bike. This may be because i only drove on Asphalt roads and bike paths.

 

[JonB]

It is a little tricky to put my Altura pannier on my midrack, but putting my Ortlieb backroller plus on is very easy. The tricky part is getting the hooks onto the midrack horizontal rod. It would probably be easier if the rod was further out from the frame, lower from the seat or both.

When i drive with my panniers on the midrack, even when somewhat loaded i do not feel that they are on the bike. It feels like it handles like the usual Cruzbike. I no longer notice if i have only the altura pannier with 1 laptop in the left side, and the right side empty. I often catch myself feeling if the panniers are still there, but so far i havent lost them, and i feel no swinging from side to side, even when i turn sharply in speed.

 

[JonB]

My pannier got a little dirty after riding on hard soil after it had rained. There was also some the day before, but alot less since i had been riding on asphalt. It appears like it is the front wheel that makes it dirty, even though my mudguards extend pretty long down.

 

[JonB]

Someone emailed me and asked for heights, so here are they:

My seat pan is 60 cm above the ground.
My midrack is 50 cm above the ground.

Both are measured with no weight on the bike.