Comments on: How Much Does Dynamo Hub Drag Really Slow You Down? Lab Testing Results https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/ Bikepacking, Bicycle Touring, Equipment, Testing, Videos Wed, 27 Dec 2023 15:08:43 +0000 hourly 1 https://wordpress.org/?v=6.5.2 By: John Harshbarger https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-4252 Sat, 02 Dec 2017 06:11:00 +0000 https://www.cyclingabout.com/?p=10930#comment-4252 I have been commuting for 10 years by bicycle and have not noticed any tangible difference between a dynohub and a regular hub. Though my commute is only 8km each way. What I have noticed that makes a huge difference are bottle dynamos. I have one bike with one and it caps my speed at around 25 km/h even downhill. If I disengage the dynamo I can easily hit 40 going downhill. Though I really don’t mind this as speed is not my goal.

Overall I feel the benefits gained from having an always on lighting system that will not run out of batteries outweighs any loss. But I ride to get around and not for sport or exercise. As my bike alone is already ~30 kg, I don’t worry about added weight.

]]>
By: Kai Jokela https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-4231 Sun, 19 Nov 2017 03:11:00 +0000 https://www.cyclingabout.com/?p=10930#comment-4231 In reply to Alee | CyclingAbout.com.

If this test did aim to same light brightness in all cases, and light output was measured with light meter, then it actually DID measure efficiency. If it didn’t measure light brightness then it didn’t give info on efficiency. But simple resistor don’t emit light! Current and voltage information together would tell power (watts) IF it was measured. Was it? If not measured then output is a mystery.

]]>
By: Alee | CyclingAbout.com https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-4230 Sat, 18 Nov 2017 21:45:00 +0000 https://www.cyclingabout.com/?p=10930#comment-4230 In reply to Kai Jokela.

You’re right, the output power comparison would be interesting. I guess the reason they didn’t test it was that output power is typically VERY close to 3W on most of the hubs (1.5W on the Shimano 1N70). You can boost the output through electronic circuitry, but it of course increases the resistance at the hub. This comparison uses the same light on multiple hubs at varying speeds.

With regards to the usage of the word ‘efficiency’, my terminology across the site tends not to quite align with engineering terminology. This is to make it easier to read and understand for people with a less technical background. In this case, it’s the power difference between pushing the pedals and the light output. Less pedalling effort to achieve the same light output being the more efficient.

]]>
By: Kai Jokela https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-4225 Fri, 17 Nov 2017 03:12:00 +0000 https://www.cyclingabout.com/?p=10930#comment-4225 There was no comparison of output power. Test did not measure how much current is going through the 12 ohm resistor. In this test/translation word “efficiency” was used strangely, and I didn’t understand did it mean drag, power or energy-in/energy-out comparison like word efficiency means.
They only measured *drag in watts*. We need to know also output in watts.
People who are using a lot of electronic devices take electricity from dynamo allways and prefer to know the electric output in watts and compare that with the drag in watts. They would choose the dynamo with highest output and with lowest drag compared to output. Just drag information is important to those who don’t need electricity.
Can you find out that info ?

]]>
By: Stelios Kalantzis https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3942 Wed, 06 Sep 2017 16:28:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3942 Thank you ,great article

]]>
By: Rod Cardoza https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3869 Fri, 18 Aug 2017 03:49:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3869 In reply to Rick Harker.

Thanks. Good to hear. The warranty replacement looks like a new generation product, so I trust it will last much longer. I haven’t used it since the rebuild. Still using the OEM wheel that came on my Surly Trucker. Much less need for a dynamo to power lights and recharge USB devices when not doing multi-day tours.

]]>
By: Rick Harker https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3868 Fri, 18 Aug 2017 03:35:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3868 In reply to Rod Cardoza.

I’ve had a PV-8 and PD-8 with premature failed bearings. Strangely the replacements have been good to date. I’m guessing bearing or assembly problems. With the noticeable drag you experienced could it be your bearings, whilst slowly deteriorating, were increasing drag subtly without being aware of it?

]]>
By: Rod Cardoza https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3616 Fri, 16 Jun 2017 23:36:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3616 I used an SP PD8X (with Marathon Supreme tires) on my Surly LHT last year touring from Vancouver, Canada to San Jose, California (2,000 km) averaging 100 km / 800 m climbing daily. As far as I know, the SP PD-8X has a much greater efficiency than the dynamos tested above. Unfortunately, my dynamo bearings failed on day 18 (2 days before we were scheduled to arrive home in San Jose). Since the hub was non-serviceable, I was forced to retire it and have my spouse bring my old wheel to the campground. After putting my old wheel back on the bike, the difference is rolling resistance that last two days was huge! My son also noticed I was riding significantly faster than usual. So while I don’t doubt the efficacy of your testing, it’s hard to believe it only added 3-6 minutes to my daily ride.

]]>
By: Tony B https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3532 Fri, 02 Jun 2017 06:48:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3532 First time I’ve seen this experiment done. Good job.

I am a keen cyclist and use a SON 28. I also used to work as an electronics engineer. So if I may be so bold as to offer a suggestion:

Most dynamo lighting these days use LEDs which are normally with switched regulators; important otherwise excessive speed would result in overvoltage and blown LEDs.

By performing your experiment using a simple 12 Ohm resistor as a load you will get slightly higher power loss than you would with a switched regulator which would limit the power going to the LED in an efficient way.

So above 20kph they would probably be less power consumed resulting in less drag.

Cheers

]]>
By: kai https://www.cyclingabout.com/dynamo-hub-drag-lab-testing/#comment-3525 Wed, 31 May 2017 20:24:00 +0000 https://www.cyclingabout.com/?p=10930#comment-3525 it seems to boil down to about 0,5 kmh slower, or if kept on for safety, around half an hour slower on a pbp. or comparable to having 20 kg extra load on a flat road. that compares to a lot of 18560 batteries. do the randonneurs know this:)?

]]>