Sumo Roller

A fun project conceived at the beginning of this year has just dropped its fruit. A fat tire bike designed by and made for myself, the Sumo Roller.

Fat-tired mountain bikes are in, with tire widths ranging around four to five inches. I see people around me hopping on the train too. I heard my inner jealousy whisper to me, “Go bigger or go home,” so I went for tire width of 12″, approximately 305mm. The outer diameter is also decently large at 25″.

The following picture shows a different angle view, assembled with some different, makeshift parts because this was the very first day that this bike rolled on the terra.

Components include those of bicycles, motorcycles, ATV buggies, etc., which are put together by adding some twist i.e. grinding and welding. There was no guarantee for this project that the concept would actually turn out functional at all, so there was some focus on avoiding costly processes and ensuring that most parts can be taken apart and reused if this whole thing didn’t work. But somehow, it worked.

So I hopped on it, and the impression was like, wow, this is absolutely and startlingly different from anything and everything… not. It’s large, heavy, good on snow, and can’t go fast. Just as it seems. Then is it fun, you may ask? Absolutely yes. It doesn’t take any special skill to ride it around, but there is no denying that the experience comes with unprecedented sights to see and unparalleled feeling to be had.

It’s been about 10 days since the launch, during which time I’ve done some 80 km in distance. I had to readjust the drive train to counter the initial stretching of the chain, but otherwise there has been no troubles, somewhat to my surprise. There actually are many parts I thought could break down anytime, partly due to the restrictions in the structural design.

Though there are some points to be fine tuned, it came out with a better potential than expected for the very first prototype. Also I managed to make it in time before the snow was gone, which made the project a great success overall. As is always the case, DIY is THE answer when you want to ride something fun and unique.

Anodizing extravaganza

My new prototype frame has come. I haven’t been able to build it for some reasons yet, but I’m collecting enough parts needed for it. Some parts like head set and bottom bracket are in different standards from the current model, so I’d just need some even if I were to just switch the frame.

I’ve already got the head set and BB, but didn’t like the logos and shapes. So I reshaped some, and re-anodized all of them.

Anodizing is a surface treatment method for aluminum. Roughly, it’s what plating is for steel. It prevents corrosion, can add color, and also improve hardness and slipperiness. Since it is a surface treatment of the metal, it doesn’t flake off like paint would. Also unlike painting, it causes little dimensional problem as the surface layer is only as thick as about 0.01-0.02mm.

Bicycle parts are being required by the market to come in more colors than ever. Thus there are a lot of aluminum parts that are painted not anodized. From industrial point of view, however, it concerns me due to the overlooked functionality. Painting should cause dimensional change due to compression or flaking of paint at points under pressure when the bike is built and used, like spoke holes of hubs, spacers above head set, and handlebars. I know it’s just theoretical, but there is a possibility that things get loose at these points while in use.

White is one of the colors anodizing cannot achieve. Nor neon and other bright colors, that would require white undercoating when you paint. Problem is white and all these light colors are popular too. So what happens is some fake-sport bikes marketed on fashion-first basis come with all parts painted white. On the other hand, there are reasons serious real bike makers don’t offer that option.

All in all anodizing is a good solution for small aluminum parts. There also are DIY anodizing kits sold out there. It’s fun, and you can mix your own color as well. So I did it for the first time in a while.

The stem is nothing special, but I just started to use it again recently and it worked fine. I rounded all sharp edges, and wanted to anodize it so it looks better than the original plain silver. The matte finish is due to chemical washing, and I like it a lot this way.

I chose Sputnik seat clamp and head set. I wanted dark blue but it turned out a bit too dark, looking almost black under dim light. Color control is a tough subject in anodizing. Even large manufacturers show some deviance batch by batch. Factors like processing time, temperature and material composition have a lot of effect.

The sputnik clamp was cast aluminum and full of burrs. So I filed down sharp edges and changed the hole shapes a little. The original color didn’t come off in the chemical washing process, and to my surprise it had been painted black. The head set is made with fair effort, but I had to file down the top surface that contacts the stem or spacer because it was a bit small in diameter and didn’t make sense to me. I filed it down by hand, to make it about 0.5mm thinner. I know this is one of the “worst DIY ideas” kind of thing, but I’m more precise than that… The highest and lowest points don’t differ much more than 0.01mm in height, so it should be fine. Besides, there are stems with the contact surface crooked by 10 times that figure in dimension.

The ahead spacers are just random ones I had. Too much deviation, but the three on the left were successful. Probably these are made of different materials, like 2017 and 6061 maybe.

The top cap on the right was hopeless. There was too much smut while being chemical washed, which looked rather due to contamination in the alloy than alloy materials. I tried anodizing in different setups a few times in no avail. Well, not very surprising for a piece of metal that I can’t even be sure about the material of, with a sketchy paint job on it, the sort that comes as part of complete bikes while costing only single digit yen probably. This poor baby may never have imagined it’d be anodized in its time, sorry if you weren’t ready yet.

On the bottom left are the BB spacer from Demolition. Despite some retries, couldn’t get the right color. I had to give up because retries would shave off the surface of the chunk each time I chemical wash them, and there was so little I could do with the treatment setup while not knowing what the material was. Oh and now, as I take a closer look there are weird cracks on the larger piece. I used to love Demolition for the riders, but maybe not now.

As a whole it was a success, and I was glad. It was better than the previous time when I got spots.

I made this pressing tool for bikes using M16 chromoly bolt. The bolt is much stronger than typical press tools from bike tool makers, and you can find replacements easily if it’s broken or you are working on much longer or shorter applications. You’ll need various adapters with 16mm holes, so I made some and bought some. Among them is the Chris King adapter I made on a lathe. The color was meant to be the same as the stem this time but didn’t turn out great. I really don’t mind though, as long as it’s only appearance. The cool thing about this tool is the thrust bearing unit (thin plates are visible). I made the adapter for this out of aluminum, so next time I anodize things I shouldn’t forget this one.

Back to the stem, I’m just going to throw away the crappy original bolts and get cap screws with strength class 12.9. Problem is, I’d need weird length bolts. As I measured and calculated, I’d need M6x18 for the front cap and M6x16 for the fork clamp. Seriously? And I have no other choice, I don’t want to use M6x15 everywhere and end up with stripped female threads. I don’t want to spend a lot of time cutting, chamfering and gun-bluing a bunch of longer bolts either. Found none in hardware stores. Screw wholesaler in town said they were irregular sizes. Hey, they are on every catalog from screw manufacturers! M6x22 too, which I need for the seat clamp!

I found them online, but most shops sell these small bolts in packages of like 200 pieces. Then I found this shop, and bought from here. Nice folks, and capable of handling real small quantity. Shipping charge will seem rather large when you buy in small quantity, but it’s better than keeping in stock boxes of weird size screws. Right now I have 14 of M6x16, 11 of M6x18 and 12 of M6x22, which should be enough inventory for these sizes for the lifetime I guess.

And you, ISO?

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Come on JIS, standardize it

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TPI (threads per inch)

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