The 585

Hey guys, just recently got a vintage Bartali bike and it's my first time having a direct contact dynamo self-powered headlight and tailight. However, when I engage the dynamo (pictured) against the wheel, it does spin and make the lights work, but it sounds like there's also a lot of friction and rubbing going on as if it's not completely spinning along with the wheel. I don't want it to completely wear down the sidewall on my tire, and was wondering if there's a way to adjust this so that it reduces the friction? Maybe a small rubber band at the contact point would increase traction while decreasing wear on the sidewall?

(Added note: it wasn't raining, BUT the road was still damp... maybe that causes the friction?) Thanks in advance!


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79pmooney

I haven't used a generator light in many decades but when I did, we always set them up to contact the tire rubber, both for better contact and spinning the generator and to protect the casing under. I see wear already in the thin coating over your casing. I'd see about orienting the generator high or using a different tire.

Ben

canklecat

That's how they worked "normally." Tire driven dynamos were a terrible system, but the least bad practical alternative to dim battery lights or miner's carbide lamps.

There were some that used rubber covered dynamos that contacted the rim rather than tires. I've never seen one in the US.

Some earlier tire driven dynamos were designed to contact the tire tread instead of the sidewall. But the most commonly seen inexpensive dynamos couldn't be adjusted to reach anything but the sidewall, so it was necessary to choose a rugged tire and sacrifice performance. But just using a tire driven dynamo was already sacrificing performance.

I tried 'em for awhile in the 1970s for commutes, but gave up and switched to the slightly less useless Wonder lights, including a red/amber strap-on doodad for the leg or arm.

Can't say I have any nostalgia for those inferior lights. If I wanted the cosmetics of a classic lamp I'd gut the housing and install an LED lamp with USB recharger. Or get a hub dynamo.

Andrew R Stewart 

Make sure that the generator's axis is in line with the wheel's axle. If the generator is off angle the "roller" will scuff and abrade the tire at a faster/louder rate. Slip on rubber caps, for the roller, have been made and do a good job at quieting down then contact. Many of these systems that were popular here in the 1970s didn't like too high a speed as it would burn out the bulb when too much juice was being created. Andy

JohnDThompson 

BITD, you could use tires with sidewalls specifically designed to work with that type of dynamo, and the dynamo could be fitted with a plastic cap to reduce wear on the sidewall. I haven't seen those items for quite some time.

I never found the sidewall-driven dynamos to be very satisfying. They were noisy, tended to slip, and required special tires (see above) that had poor ride characteristics due to the reinforced sidewall. I found that dynamos that mount behind the bottom bracket and engage the tire on the middle of the tread worked better. Even better are hub dynamos like the Sturmey-Archer Dynohub. Modern hub dynamos put out much cleaner power than the old Dynohubs.

HerrKaLeun

When such dynamos were common, tires had a sidewall thread similar to the dynamo head profile. So the dynamo engaged like a gear.

79pmooney

I had a thought. You could cut a 1/2" of a rubber tube and fit it over the generator wheel. THis would reduce slippage and partially protect the tire sidewall. Not perfect but better. The tube? Can you find a really skinny innertube? (Probably not.) I'd go to a hardware store with the generator and ask on of the old timers for a stretchy tube like an innertube. (The guy who knows what's behind those boxes on aisle D that haven't moved in a decade.)

Ben

dedhed

Put a couple small o rings on it

Papa Tom

THAT seems like a good idea!

dsbrantjr

You might try a section of appropriately-sized heater hose from the auto parts store, or old garden hose, pressed over the generator wheel.

trailangel

Would never use one of those today , as I have used them 40 years ago and they slowed the bike down. Lights were dim.
Modern stuff so much better. Small rechargeable light so much brighter and lighter.

phughes

I will add, that those tires look as if they are old. The sidewalls may have hardened and as a result, will not have as much grip. New tires would solve that issue.

There are assumptions in my reply, so if the tires are new, disregard.

Kovkov

I have dynamos on all my bikes as backup. Rechargeable lights are nice, but after some 2-3h they are done. All common tires i came across have dynamo threads



This for example is a schwalbe road cruiser.

thumpism 

"Bottle" generators, as these are called, are pretty reliable in wet or dry but drag is a real disadvantage and this style has been superseded by modern systems that are much better. I've used a rubber cap (made by Velox, as I recall) but that slowed the spin of the generator and reduced the output. I've also used bottom bracket generators but these seem more sensitive to wet tire tread that will induce slipping and reduce output. If I had to have a light set for occasional use and did not care about drag and absolutely did not want to mess with batteries or charging, a bottle generator would serve but you do need spare bulbs on hand. Most are 6V with the front bulb being 2.5W and the rear .5W. The rear usually blows out first, serving as a fuse.

*edit*

Starting fresh I'd get a hub generator and LED lights but I have enough already-paid-for old crap lying around to last me for the rest of my riding days.

gilesa

I would open it, clean and grease the bearing. It made a real difference to one that I serviced.
Changing the bulbs to LED emitters will greatly improve the brightness, especially at low speed.
There are drop-in bulb replacements by Nicelite, and a lot of home-brewing information around the web
(LED Bicycle lights | yojimg.net has lots of links).

I suspect that the perceived friction of bottle dynamos owes a lot to psychology: it's the whirring noise.
I have not seen any measurements for bottles, but figures for hub generators suggest the drag with
lights on is no worse than that caused by switching to slightly heavier tyres: a few watts.
A bottle adds its own bearing friction and tyre-to-roller friction, but it seems unlikely to have more than
double the drag.

gilesa

... and after a little more time-wasting, I did find a measurement. This article finds 29% efficiency
(mechanical-electrical) for a bottle and 60% for the best hub: https://www.ihpva.org/HParchive/PDF/hp49-1999.pdf
There is more here: DYNOTEST, where a nice graph shows that the
drag from bottles is about the same as from climbing a 1:300 incline.

Road Fan

To add clarity, the axis of the dyno's spinning should go directly through the wheel axle center.

Also, these generators are VERY simple machines. It should be possible to see where to apply a small drop of oil to help the insides.

sweeks

Heh... to add even *more* clarity, the (projected) axis of the dyno's armature should intersect the projection of the axle's long axis. This will be "in space" several centimeters from the end of the axle when the generator is in contact with the tire.
(Hi, Ken!)

AnkleWork

The drive wheel is worn out.

Road Fan

Thanks, Steve, I agree!

tcs

A more modern set-up; low cost for a bike that doesn't get ridden a lot. Axa HR Traction driving an Axa Pico 30.



300km brevets? No! Evening run to the store, or neighborhood ramble on warm summer nights?