Newbie looking for diy rear rack build ideas.

[wturber]

yes hollow not solid

solid would have been a better choice, but higher price.

I do have a bit smaller piece same shit just smaller, fits snuggly inside, telescopic I believe is what its called.

Epoxy (and/or rivet) a length of that into the end where you insert the bolt to reinforce it. I did something similar by inserting some wood into the main cantilevered beam of my seatpost mounted rack where I had drilled some holes for mounting two reinforcing struts that run to the seat stays. I was concerned that the thin sidewalls might deform over time with repeated stress. The wood will hopefully spread the load along the beam and take some stress off of the thin beam walls.

 

[amberwolf]

And in a hollow tube that's bolted thru a hole drilled in both walls, you want to fill the tube with something solid (wood, etc) at the hole point, so the bolt doesn't deform the tube and loosen the bolt/nut.

 

[alpharalpha]

I have had my eye on that Jandd Expedition for awhile as it's built well and is about the longest rack I've come across, but if I can find a decent steel rack instead I would be more comfortable with a steel rack. Googling weld strengths of steel vs aluminum I came across "aluminum welds are significantly weaker than a comparable weld in steel" enough that I believe it to be the case. That Axiom rack was ok but I need a rack with open loops on each end as that's how I strap the pack to the rack

 

[alpharalpha]

Thread merged into one diy rear rack build.

 

[dogman dan]

The load you are contemplating might need a more sturdy rack that that. But its steel, so it could be modified.

But if you are welding anyway, might as well make one from 1/2 inch square steel tube.

Id want to carry that much weight very low, in panniers or saddle bags.

 

[2old]

Expensive, but look at old man mountain.

 

[amberwolf]

What about the thread for racks you started back in February?

https://endless-sphere.com/forums/viewtopic.php?f=3&t=92885

 

[alpharalpha]

Thinking about it, the Minoura Gamoh would be too wide with my panniers. The other thread was specifically asking about chromoly, I thought that might exclude non-chromoly steel racks. The Minoura was an impulse, I should've thought about it for a few days before posting. I was looking for steel rear racks and it initially seemed good. Could someone link me to any posts (or explain what search parameters to enter) to research a diy rear rack build? Thanks.

 

[wturber]

I wasn't sure how much carrying capacity I'd need and was kinda figuring out my bike as it went. So my rack has been slowly improved over the last year a piece/mod at a time.

I started with a Schwinn seatpost rack and added two beefy supports that connected it to the seat stays at attachment points that look like they were intended for a rack. This was intended to reduce the strain on the seat post and reduce the length of the cantilever arm. At amberwolf's suggestion I reinforced my seat post by press-fitting and gluing a wooden dowel inside of it. I later did the same thing to the rack's cantilever boom using a length of plywood. I road with this configuration for about 1500 miles with batteries in a bag on top that weighed up to about 18 lbs.

This spring I increased my batteries to 20 lbs and mounted them in cases to the side of the rack. That freed the top of the rack up for other uses, so I decided to reinforce it more. I added two sets of struts made from 1/2" aluminum tubing from the hardware store. I attached them to the lower part of the seat stays using aluminum lighting accessory clamps sold for 4wd vehicles. I flattened the ends of the tubes to create flat sections that I could drill and then bolt to the rack's large cantilever beam. The plywood insert helps to spread the load of these bolts. This rack seems to be very solid. Since this was done piecemeal, images are posted throughout the thread that I have linked in my sig. But you can look at the final rack build by going here:

https://endless-sphere.com/forums/viewtopic.php?f=2&t=90369&start=100#p1393011

Scroll back a bit and you can see how I attached the battery cases.

 

[markz]

steel rear racks

Why dont you build your own?

 

[alpharalpha]

I've been wanting to add an extra bar to give my current rack some more support and while looking at racks found this one



It's $15 and has the supports in the lower bar that I wanted to add to my rack with the benefit of having built in connections to the rack platform. I know this isn't the best rack out there, but could I just place it over my existing rack to beef things up and give me a cheap temp' fix?

 

[markz]

https://www.metalsupermarkets.com/

https://www.metalsupermarkets.com/metals/
Hot roller is cheaper then cold rolled.

0.750 X 0.750 X 0.065 ST CREW TUBE SQUARE**
10' $42cdn

Locations
https://www.metalsupermarkets.com/store-finder/
they can cut it for you

Value-Added Services

Bending and Press Brake
Delivery
Flame Cutting
Hole Punching
Laser Cutting
Miter Cutting
Notching
Plasma Cutting
Production Cutting
Shearing
Sourcing Hard-to-Find Products
Water Jet Cutting

 

[wturber]

Also Aircraft Spruce and Wicks Aircraft can be good sources of tubing and other structural metals.

That said, I've found the aluminum at the hardware store to be plenty adequate so far. I'm sure it isn't as strong as T6 and similar tempered aluminum, but I just err toward using slightly larger pieces.

 

[alpharalpha]

There is a Metal Supermarkets in my area. I'd like something similar to this (but without the twisted bars.)

 

[markz]

twisted bars

Style Points


Flat steel would be perfect.

I did my alum rear rake in square tubing and mine fit into each other snugly telescopically, Be sure to to fill the voids with strong epoxy and strong filler.

 

[Chalo]

There is a Metal Supermarkets in my area. I'd like something similar to this (but without the twisted bars.)

Rear_Rack.JPG

That rack looks to be lacking in lateral rigidity and would probably be shaky. Putting a heavy load on a flexible rear rack makes the whole bike tend to shimmy.

 

[wturber]

Flat steel would be perfect.

Really? My armchair engineering would have me thinking that tubing is stronger for a given weight than flat bar and that round tubing would generally be better than the square tubing and should provide more of the lateral rigidity that Chalo mentioned. There's a reason you don't see often see bikes made from flat bar.

That said, I might be inclined to make the top/flat portion of a rack out of square tubing for ease of creating attachment points and or use flat bars for pieces that might fit better with thinner members - like where the rack connects to the seat stays. Speaking of which, I'd consider triangulating the seat stay attachments to increase lateral rigidity some.

 

[markz]

Flat steel would be perfect.

Really? My armchair engineering would have me thinking that tubing is stronger for a given weight than flat bar and that round tubing would generally be better than the square tubing and should provide more of the lateral rigidity that Chalo mentioned. There's a reason you don't see often see bikes made from flat bar.

That said, I might be inclined to make the top/flat portion of a rack out of square tubing for ease of creating attachment points and or use flat bars for pieces that might fit better with thinner members - like where the rack connects to the seat stays. Speaking of which, I'd consider triangulating the seat stay attachments to increase lateral rigidity some.

I dont know much neither, but you are most likely right because thinking about flexing flat bar vs square, flat bar flexes more. Round bar is ideal, but how do you bolt together. Thats why I went with alum square tubing. My thinking when posting flat bar was you could add extra supports. One support down to rear dropout, second support to seat post, and a third to say the rack mounting hardware on seat downtube. You can also buy seat post clamps with rack mounts, but most bicycles have frame mounts for rack. It might be the case that flat bar is cheaper. Maybe a combination of flat bar and square tube.

Maybe incorperate this and add to it.
https://www.amazon.ca/Ibera-IB-RA1-Bicycle-Commuter-Carrier/dp/B002T5GHNI?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duc12-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B002T5GHNI

 

[wturber]

I dont know much neither, but you are most likely right because thinking about flexing flat bar vs square, flat bar flexes more. Round bar is ideal, but how do you bolt together. Thats why I went with alum square tubing. My thinking when posting flat bar was you could add extra supports. One support down to rear dropout, second support to seat post, and a third to say the rack mounting hardware on seat downtube. You can also buy seat post clamps with rack mounts, but most bicycles have frame mounts for rack. It might be the case that flat bar is cheaper. Maybe a combination of flat bar and square tube.

Maybe incorperate this and add to it.
https://www.amazon.ca/Ibera-IB-RA1-Bicycle-Commuter-Carrier/dp/B002T5GHNI?SubscriptionId=AKIAILSHYYTFIVPWUY6Q&tag=duc12-20&linkCode=xm2&camp=2025&creative=165953&creativeASIN=B002T5GHNI

I attached round bar by flattening the ends in a vise. I used leather in the vise jaws to ensure a smooth transition from flat to round without sharp creases that might cause stress riser. I basically did what you suggested. I reinforced a seatpost based rack.

 

[alpharalpha]

If I had the space for a seatpost rack I'd do it but I don't and I use my panniers so my pack has to sit on top of the rack.


I don't know if that rack has lateral sway, it's made of 1" x 1/8" '316' stainless-steel bar stock and the guy seems to have some experience in touring,http://www.bicyclinglife.com/HowTo/HeavyDutyRacks.htm
The turns in the bar stock aren't for style, they're to stiffen up the bars. I like the simplicity of the design, though I wouldn't use stainless, corrosion isn't an issue for me and I wouldn't need to go 1" either. It'll be interesting to see what the cost is to have something like this made. I'm completely open to suggestions. (I also want to remove the welded on kickstand mount so I can put a 700x38 tire on the rear like in front, these trek hybrids are set up for 700x32 so I've got all this weight on that narrow rear tire, be great to have the 38 back there as it'll really increase my handling. Does anyone have any ideas on how to remove that mount? You can see it in the first pic.)

 

[wturber]

Yeah. I figured the twisted bars were for adding stiffness. The thing you might want to ask is whether your needs are similar to his. His needs seem fairly extreme.

I used 1 x 1/4" aluminum bars for the first braces I added to my rack. It is pretty stiff and strong stuff. My bet is that if his rack had been made from aluminum bar of the same size, it would have been plenty robust for him as well. I'm pretty sure that none of the aluminum racks he had that failed were made from thick aluminum bar like that.

 

[alpharalpha]

I'm sure the aluminum would work fine, but it can fatigue/crack so why chance it and not just go with steel, weights not an issue. It's looking like I may have to do a diy to get the rack the way I want it. I found some more info from an instructable that's similar to the one I showed before:

starting to give me some idea of how to go about this. Thinking if I'm going to be going the diy route maybe I should start a new thread?

 

[wturber]

Anything can fatigue crack. It all comes down to design and execution. Make sure you remove burrs and finish all drilled holes and cuts if you are concerned about fatigue failures - though given the degree to which your are "over-engineering" this rack, that may not be necessary.

I think you should make sure you have a support that goes from the end of the rack down to the dropout mount if you want the rack to be rigid. That said, the weak point with this rack will probably be the frame mounts that you attach it to the frame with.

 

[alpharalpha]

That's some good mounting hardware they've got there, as listed/described/pictured on the linked page. YOu could probably make a way to use that hardware with a lesser rack and have a rack that's stronger than the cheapie but not as good as the Tubus...

I have thought about using the Tubus hardware to reinforce a rear rack like this:



It would actually go behind the existing rack and panniers, just using available pic.

If I did that would regular hi-ten steel be ok, or should I go for the cro-mo?

Something to get by until I can upgrade the rear rack properly. Any ideas?

 

[alpharalpha]

I don't know if I mentioned it, but my 30ah prismatic cells are 2.7 lbs ea; 36v pack'll be about 33 lbs, so that's what'd be on top of the rack. We do have a metal supermarkets around here; they won't do the bending, but I know someone who does fabricating and am going to send him the pics of that design, have a feeling it's going to be expensive. The Jandd Expedition rack while aluminum has a large platform and I have some trust in the company--I've read they use aluminum rod not tubing if that makes much of a difference I don't know--at $100 it's a compromise, not steel but probably ok and large enough; the tubus and surly are both on the small size, well the surly nice rack is a little larger.