$20 3-speed transmission & other surplus stuff

[John in CR]

Here are some interesting things I found at SurplusCenter.com :

$20 3-speed transmission for riding lawnmower. 7:1 low to 4:1 high http://www.surpluscenter.com/item.asp?UID=2008120104583171&item=1-2950&catname=powerTrans The unit itself looks pretty compact at about 4"x3"x1.5", and after whacking off much of the shaft the shipping weight of 7lbs can probably be reduced to about 5lbs on the bike. That seems well worth it unless you're going for an ultralight build.

$20 5.25:1 aluminum gearbox reduction http://www.surpluscenter.com/item.asp?UID=2008120104583171&item=13-1064&catname=powerTrans

$5 one-way bearing and friction roller http://www.surpluscenter.com/item.asp?UID=2008120104583171&item=1-2317&catname=powerTrans

$5 steering U-joint. I was thinking this might work for the joint in the steering at the front of one of those Ground Hugger recumbents. What do you guys think, do U-joints exist that have no "slop", because I can't imagine any bike with any amount of play in the steering? http://www.surpluscenter.com/item.asp?UID=2008120104583171&item=1-2737&catname=powerTrans

Some of their electrical stuff may be useful, but I'll leave that up to the e-gurus around here. One thing I've wondered is if U-joints can be joined together in series to obtain a 90° bend. I realize it would need a bearing support in the middle of the series, and U-joints have the issue of somewhat discontinuous rotation, but if you had say 4 in series at different rotational positions could that make the motion constant enough for our purposes?

John

 

[John in CR]

Since no one posted any issues, I ordered one of those 3spd transmissions. The input needs CW rotation and is designed for 1800 max rpm, so I figure 3krpm input isn't pushing it too much. Then the 4 to 7:1 gearing range gets me down to an easy match with final stage sprockets or pulleys. What would really be slick for it would be a shaft drive rig, motor-transmission-wheel input, all in one clean line with a very slightly angled U-joint all inline with the bike frame. I haven't tracked down a reasonably priced shaft drive rig though. Anyone in Europe with contacts to pick up a shaft drive off of a crashed chainless rental bike? In the meantime, I'll just have to put a stage on each side of the transmission with motor and tranny parallel, but perpendicular to the frame.

John

 

[etard]

I like the idea of that 3 speed tranny, but the gear ratios dont make it worth the loss of efficiency from that heavy component, especially for you to travel so far. It seems you would need as much power from the batttery to the wheel as possible. The aluminum gearbox seems to be a good find, I wonder how loud these are at upwards of 2000 rpm. That U-joint is very heavy duty, I wonder if there is one from a garden tractor that is smaller and lighter. You are right, I think it could solve the ground hugger steering issues. Thanks for the heads up on that website, I am sure it will come of some use to a few of us.

 

[John in CR]

I like the idea of that 3 speed tranny, but the gear ratios dont make it worth the loss of efficiency from that heavy component, especially for you to travel so far. It seems you would need as much power from the batttery to the wheel as possible. The aluminum gearbox seems to be a good find, I wonder how loud these are at upwards of 2000 rpm. That U-joint is very heavy duty, I wonder if there is one from a garden tractor that is smaller and lighter. You are right, I think it could solve the ground hugger steering issues. Thanks for the heads up on that website, I am sure it will come of some use to a few of us.

Etard,

This is definitely not for the coast-to-coast bike. Weight isn't a huge issue, but efficiency is. For the flats, I'll compare the efficiency of a single stage chain drive to a variety of hub motors at full speed. Then it's how to get over the mountains with some long 10% grades, and a few shorter climbs in excess of 20%. Retro-direct and one motor is one possibility, the other is a helper motor just for the hills. I just don't think anything can be efficient enough on both flats and hills without gearing. I'm almost positive a direct drive hub won't, but I have some geared hubs on the way that may. These don't have a freewheel and include a regen controller, so I'm anxious to get that shipment in. Then I don't have to build for 50-60mph downhill coasting.

John

 

[etard]

Cool John,
It sounds like you will be doing alot of testing, how do you propose to test efficiency? Between grabbing up all those batteries, and now these hubs, you must have quite a few projects on the go. Jealous I am, are you going solar on your cross island trip?

 

[John in CR]

Cool John,
It sounds like you will be doing alot of testing, how do you propose to test efficiency? Between grabbing up all those batteries, and now these hubs, you must have quite a few projects on the go. Jealous I am, are you going solar on your cross island trip?

Etard,

Costa Rica's not an island. It's north of Panama and south of Nicaragua. Other than trying to time the trip to have a tail wind most of the way, I've got no solar panel plans. If I do swing a deal with Bosch maybe I can get some solar panels from them, since they bought a solar panel manufacturer in Europe not long ago. That's more likely for a second go round attempt to set a better time record, since realistically I barely have enough time to test drive trains and build the bike.

I have a pair of Cycle Analysts, so I can measure actual efficiency in wh/mi on the flats. Uphill is just math from flat results. Then once I decide a drive train I can make test rides with the highest peak only 10 miles from my house, and the toughest section is about 30 miles the other way. If the bike can do the 50 miles run from the base of the eastern range over the 1600m (5300ft) peak, across the central valley and up to the 1200m peak of the mountains to the west, then the rest of trip will just be a matter of budgeting enough batteries. My plan is to just budget for the 2 main ascents and assume the remainder is flat, giving no benefit for the downhill coasting or regen. The downhills going this direction are generally a flatter grade, so not much will be wasted in braking and I should end up with a conservative estimate of the pack required. I'm tentatively planning (hoping) that a 4kwh pack will go the 180 miles at a 25mph average. 500W average continuous, plus pedaling up the hills, shouldn't be too difficult to average 25mph on a partially faired recumbent, but I won't know for sure until I tackle the 20+ miles or so of significant ascents. Uphill eats a lot of power with a 50lb bike, 125lbs of batteries, and a 200lb rider (after my exercise and diet for the next 2-3 months of training). Maybe I bit off more than I can chew, but since I believe it's a world first, I'm seriously going for the gusto.

John

 

[John in CR]

Here's a pic of the tranny opened up. I was disappointed because the only bearing is on the shaft going to the 90° beveled gear, which is where the high speed input comes in. The main shafts just turn in greased metal bushing. It was interesting to see how it worked though, since I've never seen the inside of any transmission.

A is the shifting mechanism. The white cog slides back and forth on the shaft, and it holds a key with one "tooth" that slides through a wide groove on the inside of those 3 top gears. Whichever gear the tooth is locked in is the gear that is engaged.

B is the engagement clutch. Push that spring loaded housing the the right and the friction increases on those copper colored tooth looking things and the gears stop spinning freely.

Add some bearing to support the shafts, and get rid of that friction clutch. Then it might be useful on a bike, though not enough gear ratio range IMO, and that gear engagement "tooth" or "dog clutch" or whatever it's called seems to need beefing up for our use.

At least now I understand what Miles meant about a 2 speed planetary transmission with a "dog clutch" being something easy to do for a bike.

Please correct me where I used incorrect terminology. This is all new to me.

John

 

[HAL9000v2.0]

Nice box. Is it the one from the first link in your first post for 19$?
You can easily replace those bushing with needle bearing.
Also I see there is the place to put second pair of axle seals so you can use very light oil to make loses smaller.
I like it . I might order one just for playing with...

 

[John in CR]

Yep, they're $20. Is it common for gears that need to spin freely on a shaft not to have bearings? My thought for a homemade 2 speed is to have the 2 gears that need to alternate spinning freely on bearings, and then have the dog clutch engage the gear somewhere outside of the bearing radius. Is that more typical, or do you just need hard metal to proper tolerance and some lube. BTW, this thing had a lot of grease plus a little liquid oil too.

John

 

[HAL9000v2.0]

It is all about how long you want it to last...

 

[etard]

Nice pic and tutorial John, I still don't understand the dog clutch. Can you post a close-up of that part for clarification? thanks

 

[John in CR]

Nice pic and tutorial John, I still don't understand the dog clutch. Can you post a close-up of that part for clarification? thanks

I'm not sure what it has is called a dog clutch. The shift linkage is at A. It pivots above A at the spring. That piece of metal coming down just to the right of the A is actually a C shape. The white thing that looks kind of like a gear just below the A is one piece going all the way to the gears. That C shape has it's ends in that grooved ring, which is currently about centered on the white gear and slides left and right over the white thing. Attached to the ring is something like a key in a keyed shaft that runs parallel along a grove in that top output shaft. That key has a single tooth. The gears have a notches in them that the tooth can slide through to get to be able to get to the other gears. When that tooth stops in a gear's notch, that's the gear you're in, because the key and tooth lock the gear to the shaft. Keep in mind that the lower gears spin the same rpm, and when they are spinning all of the gears are spinning. The top gears are each spinning at difference speeds, so that key and tooth thing act like a dog clutch and lock a single upper gear to that upper output shaft making it spin, leaving the other 2 upper gears to spin freely on the shaft.

Actually after looking at wikipedia, http://en.wikipedia.org/wiki/Dog_clutch , that key thing is a dog clutch. I like the example they give of the dog clutch for a microwave oven spinning platter. The platter has 3 indentations which match up to a 3 sided protrusion on the floor of the microwave. Together they form a dog clutch to make the platter spin. It doesn't work by friction. In this lawnmower tranny, the bottom shaft also has a friction clutch to make the gears start spinning when you grab the go handle on the lawnmower. The key/tooth thing only has 3 positions, so it is always locked in one of the gears.

I hope that was more clear than a mud pie. Much easier to see it in person to understand.

John



John

 

[DeathBlade]

I might try to use one of these three speeds on my bike with another 2.125:1 gearing from 16T:34T chain for a nice 15.1 first gear can feel the hill climbing power now!
As for the bushings you could replace them with teflon or bronze bushing for now they will last longer than the looks like steel or alumium ones.
The one thing I'm wondering about is the :white cog" plastic?
With the addition of a freewheel to one side of the output we could remove the friction clutch, or even modify the friction clutch in crude type of dog clutch.

 

[John in CR]

The white "cog" only provides a sliding path to keep the ring to which the "dog" is attached true and straight.

John