Water-cooled Sturmey Archer drum brakes

[Marc]

My e-assisted trike is fairly heavy (big battery and panniers) and I got some nice hills on my daily 60+km commute.
Hence my 90mm drum brakes see some heavy use (why do street planners place pedestrian crossings and red lights right at the bottom of the best downhill courses?). The 24" front wheels also make it quite a bit harder for the brakes.

While I don't have problems with actual brake temperature, I have to clean-out the dust that gets worn off the brake pads regularly at least every two month, to keep brake performance in check. Since I prefer to ride my trike and not waste too much time with maintenance, I was looking for an easy solution.

Some velomobile riders in southern Germany and Austria use water-cooling to tackle steep descents without overheating brakes, they also mentioned an immediately improved brake performance after squirting some water into the drums. Velomobilize.at in Austria offers a water-cooling solution already, but AFAIK there are no images available.

Two weeks ago, I've installed some nipples (RC hydraulic nipples with M3 thread) into the brake plates, zip-tied a syringe to the bottle holder and tried it out. It works! Quite well actually! One or two squirts of 15-20ml of water is needed to clean both brakes.


The test rig. The left brake is water-cooled as well

Riding around with the funny syringe for a week, I've installed a water tank (RC plane fuel tank) and clyster ball 'air pump' last week.

More images in my blog post: https://etrike.wordpress.com/2018/08/13 ... um-brakes/

[[XAP]Bob]

Is it the plates that get hot though? I'd have thought your want the water getting pushed past the spokes onto the drum itself.

[Marc]

The water get squirted through the holes in the brake plates directly into the drums.
The whole 'system' is actually an instant brake cleaning solution with cooling ability.



If you squirt water from the outside on the drums, you only get water spray in your face and the crud responsible for slowly deteriorating braking capability stays inside the drums. That crud is actually the stuff that sticks to the brake pads, glaces over and you have to scrub it off manually it when you clean your brakes.

[[XAP]Bob]

Ah, I missed that bit... I blame... the phase of the moon, or something...

That's certainly an ingenious way to add rain to another wise weatherproof brake

[Marc]

That's certainly an ingenious way to add rain to another wise weatherproof brake

Thats exactly what I thought as well when I came across some postings regarding water-cooling drum brakes in velomobiles in the German recumbent forum.

I thought the squirt of water would have a negative effect on braking performance (like I've experienced with disk brakes), but it didn't, or only for a very, very short time.

I've tested it by going downhill at some 60km/h, did a short braking to get a feel, got up to the same speed again, squirted water in the brakes and braked immediately afterwards (all good), squirted more water, braked again and felt noticeably improved brake performance. Not just a little, braking performance was great!

Don't forget, I use 24" front wheels:

[[XAP]Bob]

I was being somewhat facetious... water from your bottle is clean, and applied to already hot brakes in a controlled fashion.


Rain is normally accompanied by spray from the road, grime and grit... it’s also uncontrolled - meaning that you have start with water between the brakes and the hub.

Although I assume you have to push water in between braking efforts, so that probably still applies a bit. I guess a lot of it gets boiled off though.

[Marc]

Although I assume you have to push water in between braking efforts, so that probably still applies a bit. I guess a lot of it gets boiled off though.

Like I wrote in the first post, heat is actually not my problem. I couldn't detect any hissing sound from the brakes when injecting water.

Its the worn-off stuff from the brake pads, that will accumulate over time in the brakes and leads to slowly deteriorating brake performance. The injected water just washes the dust out of the brakes and also cleans the brake pads.

Riding a fast and heavy etrike with 24" wheels usually around 1,300km a month in traffic, is a bit more taxing for the brakes than 'usual' use.
I also don't accept only so-so brake performance.

[UpWrong]

Interesting. Any risk of corrosion e.g. to the drum shoe pivot?

[atlas_shrugged]

I can confirm that there are some good reports of the solution posted by @Marc. In 2016 at a velomobile seminar in Dornbirn Austria this system was described. Both the Austrian and Swiss riders were pleading with the Dutch and German manufacturers to have a better brake cooling method. Several users reported mechanical failures (broken spokes etc) when traversing the alps without using any cooling system. Probably the most worrying one being the drop in braking performance when the drums are red hot.

The water squirting method was not reported to reduce braking performance. Probably most of the water is instantly converted to steam with the surplus dribbling out and taking any crud with it. Many trike wheels are cambered which will assist the outflow.

[Marc]

@atlas_shrugged: I remember one velomobile rider (with a Milan?) wrote about his yellow discolored spokes. If you know tempering colors, that indicates a peak temperature between 200°C and 230°C! https://de.wikipedia.org/wiki/Anlauffarbe (the German Wiki has better graphics).
That where just the spokes, I guess the drum hub body reached around 300°C.

That's why Ginkgo Spezialradteile developed their SA+ drum hubs with heat sinks (several versions) in 2016:

https://www.ginkgo-veloteile.de/ginkgoshop/en/home

At the time, I called Lutz from Ginkgo on a different matter, we chatted about their brand new SA+ hubs and I've put the infos and links to the SA+ hubs in a blog post: https://etrike.wordpress.com/2016/06/09 ... heat-sinks
Lutz mentioned, that he couldn’t raise the hub temperature of the SA+ hub prototypes above 160°C in his tests. (Lutz and Jörg, the owners of Ginkgo, are recumbent riders and really nice to deal with, btw)

[brynpoeth]

Perhaps some ducts/intakes could be used to air cool the brakes (no moving parts, simpler?)
Or does water have better cooling properties?

[Marc]

Perhaps some ducts/intakes could be used to air cool the brakes (no moving parts, simpler?)
Or does water have better cooling properties?

Water has vastly better cooling properties than air. But like I wrote before, heat is not my problem. The the stuff that gets worn off the brake pads is.

[[XAP]Bob]

Perhaps some ducts/intakes could be used to air cool the brakes (no moving parts, simpler?)
Or does water have better cooling properties?

Water takes 4200J/degree/kg
Air takes 720J/degree/kg

Additionally water is significantly more dense, so you get more water around something, and has better thermal conductivity...

[brynpoeth]

Perhaps some ducts/intakes could be used to air cool the brakes (no moving parts, simpler?)
Or does water have better cooling properties?

Water takes 4200J/degree/kg
Air takes 720J/degree/kg

Additionally water is significantly more dense, so you get more water around something, and has better thermal conductivity...

Does air have advantages?

[[XAP]Bob]

Perhaps some ducts/intakes could be used to air cool the brakes (no moving parts, simpler?)
Or does water have better cooling properties?

Water takes 4200J/degree/kg
Air takes 720J/degree/kg

Additionally water is significantly more dense, so you get more water around something, and has better thermal conductivity...

Does air have advantages?

Erm... it’s readily available, and doesn’t damage most stuff as water can in the event of a leak...