hillzofvalp

I am doing a project which calls for putting batteries that are 26mm wide into the seat tube. My issue on my chromoly frame is that the (braze-on?) steel, threaded mounts protrude on the inside of the frame around 3-5mm. Is there a way to file these down without removing the mounts or hurting my frame/paint? It's a bianchi frame with columbus tsx, and the last thing I would want to do is damage it, but I would really like to take a little bit of material off on the inside of the frame.

I think that total threaded length is 8-10mm, so minus 2-4mm shouldn't effect cage mount robustness too much, and I won't be using them to carry heavier loads anyways.

thanks!

thirdgenbird

your not putting a di2 battery inside a vintage frame are you?

hillzofvalp

no. I'm putting a123 26650 cells as part of an ebike project. May use to power solely lights, however. around 24V 2300mah in the seat tube (59cm frame).. and more capacity in bottles/elsewhere. Trying to maintain vintage '95 clean look.

And to anyone who wants to judge any sort of ebike hybrid, please do not post. other topics such as these are ones this thread is not oriented towards fueling.

I am trying to shave off inner-seattube threaded mounts a mere 3-4mm with full respect for preserving vintage frames. Suggestions are welcome!

thirdgenbird

i wondered. i believe di2 cells are pretty small in diameter after they are out of the case. (small enough to go in the seatpost itself)

unterhausen

I don't see how you are going to do that without risking fairly severe damage. If they were installed properly, there will be very little loss of strength. What is the diameter of a battery pack relative to 27mm? I'm not judging you, but I don't see the point, just put the batteries on a rack.

hillzofvalp

The batteries are 26mm, as stated above. And they fit pretty well, actually. The seattube is the kind that accepts 27.2mm, and I believe it gets a little bit wider in the middle portion. Thoughts I had on removing: File with attachment stuck down seat tube?? Long Drill attachment? A <1" door knob type drill bit?

I'm actually starting to feel that debrazing them may be an option, because this frame has seen better days. I recently had to get the dropouts realigned because of a nasty wheel lockup and crash.

But I don't think that it's impossible to remove them without damaging paint or structural integrity.

I might add that putting the batteries on a rack would not serve the purpose of maintaining a minimalist design. I encourage anyone interested to try to think out of the box.



update, an idea I'm having is the use of a hack saw blade tied to some picture frame wire. Kinda like flossing teeth.

unterhausen

good luck, but be warned it's incredibly easy to cut through those tubes.

If you really decide you don't care about the frame, the best thing to do is to drill the fittings out.

hillzofvalp

Thanks for you input.

The thing is that I still want to use the non-problem threads for cages. There has to be a safe way, while tedious, to get the job done while also keeping the mounts at least half-functional.

If there was a drill bit that I could stick in and then expand so I'm drilling backwards, that would work! (think dollys or other drywall mounting hardware, but a drill bit)

Or I could put a dremel bit through the mount from the inside, then attach it to the dremel and fire it up. Thoughts?

diamond bits:



I would have to cut off around 5-10mm probably to get the right hole entrance angle. then I could tape a piece of string to it and thread it through the hole. Seems pretty safe to me.

schooner

it seems that even if you take boss material from inside the seat tube, you will still have the bolts holding the cages protruding into the tube if you are wanting to still use the cages. I mean, in theory, you could get crazy short cage bolts as well, but I would not trust those to hold a cage and full bottle without a few threads of engagement.

NoReg

That's easy. You get a hole saw of the correct diameter, with the finest teeth you can find, and you mount it on an extension and ram it down in there, and saw it off. There are bunch of things you can do to make this work better or worse. Cheaper or not. But if you are asking this question you probably can't pull it off. What you probably could manage is spinning it on dril first, and holding it against some abrasive to get the outside set off to minimize the chance of tearing up the tube. Use lube, and try to get it started as near to the wall as you can because once you get a kerf in there, you are going have a harder time starting it anywhere else.

hillzofvalp

For clarification I was not looking to pull it out. Just shave it down 3-4 mm, maybe not even flush with the inside tube. The hole saw was my first idea, but I wonder if it would be controlled as this dremel idea. When I think of hole saws I'm worried about extra material from all around the area rubbing off. However, it does seem like an easy solution if it can be made safe

For cages I was thinking shorter bolts with thread lock if necessary. There'd still be 40-60% thread left.

unterhausen

I don't think that I would want anything other than a smooth surface to poke into my batteries. Pretty sure A123 will still catch on fire if they have something sticking through the case.
On another note, TSX seat tubes are .6mm thick. If you don't cut through the tube you are going to cause bulges. Look at this thread for example. Since the forces are not symmetric, I think a hole saw will end up denting the tube or getting stuck. If it doesn't end up toothless first.

I can see some sort of elaborate holder for one of the Dremel flex shaft holders working.

unterhausen

I don't think that I would want anything other than a smooth surface to poke into my batteries. Pretty sure A123 will still catch on fire if they have something sticking through the case.
On another note, TSX seat tubes are .6mm thick. If you don't cut through the tube you are going to cause bulges. Look at this thread for example. Since the forces are not symmetric, I think a hole saw will end up denting the tube or getting stuck. If it doesn't end up toothless first.

I can see some sort of elaborate holder for one of the Dremel flex shaft holders working.

hillzofvalp

U don't think the dremel bit shaft sticking out of the frame would work? Its 10 dollars and requires no jig or flex cables..

Lifepo4 batteries are far from being as flammable As lipos. They're alsoless easy to puncture. If there was any indication of rub, I would be able to tell and deal with accordingly

I forgot they were less than a mm thick. That's scary ( need to get granddaddy (<--- iphone meant framesaver hehe) going.

I was only able to find 25 and 29mm bimetal hole saws. I bought
The 25mm figuring I'd use it for something someday but I am now hesitant to use it. Going to check sears for the above dremel bits.

NoReg

There are a number of ways you could ensure the hole saw would not touch the inside. If a 1" saw is tight enough, just sleeve it in tape, and ram it down. Other ways might require a lathe.


If you can shorten a bit enough to guide it through from the inside that might work. I don't know if stuff like diamonds will work, you need a cutter that takes chips and doesn't clog.

I wonder if a hack saw might not be the easiest. They make a type of saw that is about 1/4" wide and about 6 inches long, the original brand was Eclipse, but most of the current stuff are copies from China. The blades have little metal cross pin in the end. I would cut about four inches of it so that the remaining pin was on the cutting side of the teeth. I would file one half of the pin off, and then I would mount the remaining pin in a hole in a shaft that would allow flush cutting. Exactly what that rig looks like, from tape to brazing, I leave to you imagination. Then I would stick it in the tube and carefully cut it so that it folloed the wall into the side. It might take two such saws, as I think the tendency might be fore the saw to get about 1/2 through and then bind.

hillzofvalp

I tried the 25mm one gently and I didn't trust doing this method. adding tape to increase diameter would only be able to cut off portion. the hole saws I found don't have fine teeth and are not appropriate. I can see these bits tearing apart the frame very easily.

I will go ahead and order some of these bits. They must be specialized for home depot, menards, nor sears had them. Do you think one of the above pictured would be preferred over the other (inverted cone vs bur). I've used diamond dremel bits for this kind of material and they are well suited-- they just won't last forever

merlin55

you want a 1 inch, carbide tipped hole saw. they are used to cut holes in tile, and do not have teeth...use the tape to increase the diameter, and lube the tape before inserting into the frame...take you time and cut a little at a time, then use you dremmel tool method to smooth up the inside

NoReg

All you have to do is grind off the outside teeth, or the points thereof, and it will be incapable of doing any damage to the tube. I have had bad luck with those carbide grit tools, but I did try them again this summer, and boy have they improved. One thing I do to make small handles is shrink tube over 5 minute epoxy. That would be another way to get the diameter centered.

Just by the by, since I know nothing about ebikes electrical needs, do you need to put in so many bateries you couldn't put them up in the seat post? Or would the weight be too high?

hillzofvalp

Battery weight is not really an issue with these particular cells, and lower center of gravity is always better, though not crucial. Space is an issue if you want to minimize bulk and have longer lifetime of cells, so lipos are out. but that's off topic.

Anyone know whether aluminum oxide/tungsten dremel bits (such as part 921) would be better than the diamond type kind above? (7117 and 7120 part numbers for diamond)

@merlin55 : please link me to a good example of a fine tooth hole saw. When I was at Menards, Home depot, von tobels, and sears, today, I couldn't find any "fine tooth" ones. I didn't look in tile section though.

gaucho777 

I'm sure you've asked yourself this, but isn't there enough room between the bottom of the seat post and the top water bottle mount. How many batteries are we talking about? Total inches needed? Maybe just trim the bottom off your post, if you can spare an inch? Can you place the batteries below the mounts and just run the wire up the tube? But more importantly, why this frame? I'm sure you love the bike, but there are also many fine steel frames which do not have seat tube water bottle mounts. Why risk damaging the frame when other more suitable frames are available?

That said. I've heard of people reaming out stuck seatposts. Couldn't the mounts just be reamed the same way at a machine shop?

hillzofvalp

I would like to try another frame but it wasn't in the budget go begin with. If you have any suggestions for Fe or Al frames with good value and no seat tube mounts for under $250 and 58-60cm let me know. Might try brothers old cannonale touring.

As for the batteries-- they need go all the way down the seTtube AND I might need to cut less than an inch off the post. Each cEll is 6.5 cm x7 cells plus around 5cm gap space. Plan is to ground pack near the bottom bracket and run the positive lead up and out of top of seat post.

Other frAmes migh have an advantage in that cells could be placed in other tubes as well, but the limitation for the Downtube is the bb. An off topic question: is it safe to drill a 27mm hole in bb or is the only way to get batteries in ther be to build the bike up with them already in place?

I love this frAme, I do. But if I can make a small modification and not damage it then I rAther not get Another frame.

Canaboo

The way you file them down is with something called a file. Really. Why don't you just jam a half round metal file onto a handle so you can reach it down the seat tube and file down the projection however much you need to?

unterhausen

I have a bike with a star shape cut into the bb shell, and the points may describe a 27mm circle. You need to find a bike with an eccentric bb.

hillzofvalp

Good point about the file, Canaboo, I can't believe that I didn't consider it from the start. However I don't know of one that would reach 16+ inches, though I do know of the sort you speak of.

Canaboo

Buy a half round that will fit inside the seat tube and get a section of 3/4 inch hardwood dowel to function as a handle. Drill a hole to accomodate the tang of the file. Tightly sleeve a piece of copper pipe around the end of the dowel to support it from splitting and drive the file into the dowel. You can notch the tang of the file a bit to give it a bit of grip.
Then go to work on the protrusion.
Way faster and more controlled than the other suggestions.