Newbie looking for diy rear rack build ideas.

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wturber   1 MW

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Re: Looking for a chromoly rear rack, any suggestions?

Post by wturber » Mar 10 2018 10:54pm

markz wrote:
Mar 10 2018 8:40pm
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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
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viewtopic.php?f=2&t=90369

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Re: Looking for a chromoly rear rack, any suggestions?

Post by amberwolf » Mar 11 2018 2:52am

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.

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Re: Looking for a chromoly rear rack, any suggestions?

Post by alpharalpha » Mar 22 2018 11:38am

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
IMG_0285bikefromrear.JPG
IMG_0285bikefromrear.JPG (81.55 KiB) Viewed 924 times
IMG_0294a.JPG
IMG_0294a.JPG (103.7 KiB) Viewed 924 times

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alpharalpha   100 W

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Looking to build first time diy rear rack

Post by alpharalpha » Jul 06 2018 6:16am

Thread merged into one diy rear rack build.
Last edited by alpharalpha on Jul 15 2018 2:53pm, edited 2 times in total.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by dogman dan » Jul 06 2018 8:22am

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.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by 2old » Jul 06 2018 9:13am

Expensive, but look at old man mountain.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by amberwolf » Jul 06 2018 5:49pm

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

viewtopic.php?f=3&t=92885

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by alpharalpha » Jul 07 2018 5:35am

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.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by wturber » Jul 07 2018 11:08am

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:

viewtopic.php?f=2&t=90369&start=100#p1393011

Scroll back a bit and you can see how I attached the battery cases.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by markz » Jul 07 2018 12:05pm

alpharalpha wrote:
Jul 07 2018 5:35am
steel rear racks
Why dont you build your own?

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by alpharalpha » Jul 09 2018 8:25am

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
1rack.jpg
1rack.jpg (78.8 KiB) Viewed 965 times
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?

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by markz » Jul 09 2018 9:45pm

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
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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by wturber » Jul 10 2018 2:47am

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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by alpharalpha » Jul 10 2018 10:46am

There is a Metal Supermarkets in my area. I'd like something similar to this (but without the twisted bars.)
Rear_Rack.JPG
Rear_Rack.JPG (23.26 KiB) Viewed 928 times

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by markz » Jul 10 2018 1:11pm

alpharalpha wrote:
Jul 10 2018 10:46am
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.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by Chalo » Jul 10 2018 1:16pm

alpharalpha wrote:
Jul 10 2018 10:46am
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.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by wturber » Jul 10 2018 7:12pm

markz wrote:
Jul 10 2018 1:11pm

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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by markz » Jul 10 2018 7:21pm

wturber wrote:
Jul 10 2018 7:12pm
markz wrote:
Jul 10 2018 1:11pm

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-Bicy ... B002T5GHNI

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by wturber » Jul 10 2018 11:10pm

markz wrote:
Jul 10 2018 7:21pm


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-Bicy ... 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.
fullyTriangulated_SM.jpg
fullyTriangulated_SM.jpg (156.52 KiB) Viewed 888 times
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by alpharalpha » Jul 11 2018 11:02am

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.
IMG_0094.JPG
IMG_0094.JPG (62.74 KiB) Viewed 874 times
IMG_0096.JPG
IMG_0096.JPG (47.71 KiB) Viewed 874 times
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.)

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by wturber » Jul 11 2018 12:32pm

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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for steel rear rack, is the Minoura Gamoh good?

Post by alpharalpha » Jul 15 2018 2:17pm

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:
rack design pic 4.jpg
rack design pic 4.jpg (111.24 KiB) Viewed 826 times
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?

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Re: Newbie looking for diy rear rack build ideas.

Post by wturber » Jul 15 2018 5:42pm

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.
"Commuter - DC Booster"
Iron Horse 3.0 hardtail - 48V / 1000W / 470rpm generic Chinese DD Hub motor (ebay)
8 x 36v 4.3ah 10s 2P battery packs - 1500W 30A DC Boost Converter delivers 54v and about 1000 watts peak
53T/42T Sakae Road cranks - 30mph+ on flats
viewtopic.php?f=2&t=90369

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Re: Looking for a chromoly rear rack, any suggestions?

Post by alpharalpha » Jul 18 2018 2:54pm

amberwolf wrote:
Feb 19 2018 7:50pm
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:
bike rack mod.JPG
bike rack mod.JPG (79.3 KiB) Viewed 786 times
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?

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Re: Newbie looking for diy rear rack build ideas.

Post by alpharalpha » Jan 31 2019 9:54am

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.

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