Spindles
 

I am looking to build a custom drive train for a human powered submarine. I will be using cranks to generate power from pedaling. Due to space limitations within the submarine hull, I am looking for the shortest possible spindle length that is available. In other words, I need the person's feet as close to each other as they can be. Can you purchase spindles separately? Do short spindles exist or are they all standard length?

Thanks for any suggestions.

Like the C.V.S. Hunley?

Spindles can be bought separately.

Most bottom brackets sold today are one-piece cartridge types; can I gather from the question that you want just the spindle and will use the cups and cones somehow to mount it?

I think the shortest spindle I have ever run across is about 105mm. Maybe something that was track specific could have been a couple of mm's less than that.

Depending on how reliable you needed this thing to be, you could maybe grind down the end of a spindle to save a few more mm's.

Please, please show us pictures or plans or something so that we can see this beast you are building!!!

jim

I apologize, but I have no idea what that is, and a quick google search did not help out either.

I've uploaded a screenshot of my cad design to try and portray a better of idea what we're doing. The spindle will be mounted somehow statically to the two plates, allowing the attached cranks to spin freely.
In the design, the spindle is floating, unattached to the plates, due to the fact that I don't know exactly how they work. Hubs often have mounting hole patterns. Do spindles have these as well?

http://www.ufhps.org/drivetrain.jpg

you can get 103mm spindles. you need to look out for the taper (if a square taper spindle) if you're trying to match a hole. edit: you may just want to get a sealed bottom bracket; it has the bearings and everything and the spindle in one unit.

could you possibly provide a link to a company who sells that item or detailed description of what i should be searching for? I don't have very much knowledge of bike parts and terms.

Also, understand that the spindle will be submerged in water at depth. A sealed spindle would obviously be better for this type of application. I am under the influence that US spindles are unsealed and euro spindles are sealed? Is that correct?

If this is serious, I would recommend you buy a bottom bracket shell, or fabricate one. It's part of a bicycle frame; it's the short, threaded tube on the frame that the bottom bracket (with spindle) is put into. The most common size shell is 68mm, measured end to end, and "English threaded," which means the right side is reverse threaded to prevent the bottom bracket from unscrewing from the shell, and the left side has the threads going in the normal direction. Weld the bottom bracket shell to something in the submarine (can't believe I just typed that), and then install a catridge bearing bottom bracket into the bottom bracket shell to attach the crankarms to. Bottom brackets are available with various spindle lengths, and they have to match the crankset you use in that the crankarm/spindle interface have to match (square taper, ISIS, Octalink, etc)...........But submerged? You're gonna have to engineer around that and keep it relatively dry, no bottom bracket assembly, at least one intended for bicycles, is going to be watertight when completely submerged.

What he said.

so-called "sealed" bearings are not really sealed. Not even close, in fact. They are "sealed" in the sense that they cannot be opened to adjust or regrease. Off the cuff, I would say that neither type of bearing will keep water out at all if submerged. Since that goal cannot be accomplished with bicycle bearings, the goal might as well be to limit the damage of running in water. Two thoughts on this: first, you could just accept that this aspect of the design is imperfect and expect to have to repack and replace the bearings frequently. Second, maybe an older style cup and cone bearing would allow more water movement OUT of the bearings when not submerged, so maybe it would last longer.

You asked about the terminology I was using above. So, let me try to explain a couple of terms I used. A bottom bracket is the entire axle assembly that connects the crank arm of one pedal to the crank arm of the other. I suppose it includes the spindle (the axle, really), the bearings that the spindle spins in, and the section of the frame that houses both. A cartridge type BB has the spindle and "sealed" bearings as one unit that cannot readily be opened up and re-greased. The older type of BB allowed the bearing races (the cups and cones) to be taken apart for adjustment and re-greasing.

Looking at your design, I might suggest thinking about just cutting the entire BB assembly out of a bicycle frame and welding it on. Also, note that in your design the spindles extend considerably farther outboard of the crank arms; bike spindles will not do this, so you do not need to account for this added width. Also, older crank arms typically did not have any outward bend to them, so they rode closer to the frame. As such, they would help reduce the overall width of the pedalling space.

Keep us updated on the project

jim

Ohhh, another thought: there are titanium and aluminum spindles. So, they would not rust. And ceramic balls would not rust. That just leaves the cups and cones. Are any of them made of aluminum or titanium?

j

Sorry for three msgs in a row, but I keep mulling this over in my mind.

Spindles come in different overall lengths, but unfortunately the distance between the two bearing races is always the same distance. (Is this true? Anyone? Strange variants out there? One-piece ashtabula cranks? Remember the old Viscount/Lambert press-fit BB's?) So, the only way to reduce that distance might be to have a machine shop fab up a spindle with a shorter middle section. Machining the faces on the end would be a snap, as would threading a hole in the end. But machining the little rim that the unsealed bearings press on would be very hard (very tight tolerances, and would have be surface hardened). It occurs to me that if you used cartridge bearings, this rim would be unnecessary. So, the machining of a special, shorter spindle would not be too hard.

Is this machine intended for use in a relatively short engineering competition? Or are you planning on building a practical sub to be used for longer periods (are you planning on running the Union blockade or something?). If the first, I would think that are some options that would work. If the second, then I think you need to go to BushnellsturtleForums.net to get answers about seaworthy bearing solutions.

j

You mean the Hunley? I don't know about the C.V.S. part, but the Hunley was a Civil War submarine http://en.wikipedia.org/wiki/H.L._Hunley and Google knows a lot about it.

Or are you thinking more in terms of Bushnell's Turtle? http://en.wikipedia.org/wiki/Turtle_(submarine)

You could also buy a cheap used bike for 50 bucks and take apart the bottom bracket to see how it all works.

Here's some How To:

http://www.parktool.com/repair/readhowto.asp?id=94


Are you going to submerge a bicycle chain, too? Bike parts won't last very long if you submerge them. I don't even want to think about if you're talking salt water, here. Maybe consider a shaft-drive or belt-drive?

Please keep us updated on this project!

73mm bb shells, very common on mtb's. Also, there's outboard bearings, which have been resurrected in recent years, which put the bearings outside the shell. I don't know how it would make much difference for the OP's purposes, though. But I am kind of curious as to the water inside the hull of the submarine. I take it this water that's going to come in is the ballast that will allow the submarine to dive, but it seems surprising that there wouldn't be a separate ballast tank or compartment for that. Put it this way: I'm not sure I'd want to take a ride in this particular submarine.

Thanks for the generous number of suggestions. To explain a little bit more to any of you that are now interested...

The submarine is a 'wet' submarine, with a completely encapsulating hull. The pilot will breathe off a scuba system which is integrated into the sub. Because there will be water inside the submarine hull at all times, the entire drive system will be in contact with water. This includes the crank, spindle and bb, as well as the cogs and chains. Last year we ran into problems with our chain slipping on the cog teeth at depth due to the fact that the chain was not tight enough (we used wood for supports and it deflected under load). We are looking into eliminating the chains all together. Since we are developing a more structurally sound drive frame this year (aluminum), we should not experience issues with chain tension, if we do choose to use them.

From your suggestions, I feel that the more feasible solution might be to machine our own bottom bracket, with appropriate threading which can be welded onto the frame plates. We can purchase a spindle (103mm are the shortest suggested) to insert. We already have 5.5'' cranks which have little bend in them which we should be able to use.

If anyone else would like to offer additional suggestions on the solution (or corrections), feel free.

I guess I missed a component in my list... the 'catridge bearing bottom bracket' is what threads into the bb shell, and has a spindle built into it. Correct me if I'm wrong. Is this an example of a 'catridge bearing bottom bracket': http://harriscyclery.net/itemdetails.cfm?ID=2140 ?

Yes, that's a cartridge bearing bottom bracket that will work with a crankset that's designed for use with a JIS square taper bottom bracket (very common). As already discussed, it threads into the bottom bracket shell, with the right side being reverse threaded. But it is not suitable for underwater use (as noted, no bicycle bottom bracket is suitable for that). You'll need to figure out a way to keep the assembly relatively dry-

Sounds like a shaft drive would be better than chain.
You may be able to work out a "wet " bearing using teflon impregnated nylon. My friend used it to make the bearing of a telescope mount and it rotated reasonably well.