Stupid Reservoir Idea

aaronb · January 16, 2009, 07:53:48 PM

I have a few comments to add.

first, along with the obvious pumping volume, thermal expansion also needs to be considered when determining reservoir size. brakes are an open system, when they heat up the fluid expands and the excess volume is displaced into the reservoir. when the brakes cool and the fluid contracts it is drawn back in. so any home made reservoir will have to have enough volume to accommodate that. also it will need to either be vented to the atmosphere (not a good idea) or have a diaphragm seal to allow the fluid to move easily into and out of the reservoir. if vented to the atmosphere the fluid will absorb moisture from the atmosphere and you would risk spillage (obviously). running into either end of the reservoir would be really bad news, no brakes or locked brakes.

i could not imagine a piece of 22 mm (OD) tube welded to the handle bar having sufficient volume to work properly with the front brakes of a modern sport bike.

second, dot 3 or 4 is fine with aluminum. the calipers, masters and light weight line fittings are all aluminum and if you were to open them up they are usually uncoated bare aluminum. in fact i just rebuilt the 28 year old caliper on the honda and once i got the pistons out, the interior of the caliper was pristine and shiny. entrapped water can cause corrosion, specifically with iron automotive calipers (bleed early, bleed often).

third, those ISR's are pure sex

fourth, good job on your res. TAftonomos, i like it.

this is not an area to play around with if you do not understand the mechanics involved with pushing those little pads into that spinning rotor. be safe.

TAftonomos · January 16, 2009, 08:43:41 PM

Just to clear it up, thats not my work, but someone elses I posted an image off of. I was just showing another way of mounting a resi, not wanting to take credit on someone else's work (wasn't the intention).

Good to know about brake fluid and aluminum!

Norm · January 17, 2009, 08:05:41 AM

You don't need much volume for any of the current brake systems, but you will always have a little air at the top of the system and the thermal expansion definately has to be accounted for (although very little). With that tiny about of air at the top, the lean alges of modern sport bikes does create a problem - again, FHE.

Bill in OKC · January 17, 2009, 09:11:38 AM

I'm slowly replacing mine - 2 of 3 so far - with the Rizoma reservoirs. The reservoirs are nice, but I really like the clutch & front brake brackets.
http://www.pjsparts.com/catalog/product_info.php?cPath=267_46&products_id=632

aaronb · January 17, 2009, 10:26:48 AM

OK, this is the first time i have ever actually put numbers to this.... if you see an error, please feel free to correct me.

IIRC the pistons in most 4 pot MC calipers are 34mm each, lets say each piston needs to move 1mm to apply full stopping force...

(17mm^2 x 3.14) x 1mm x 8 (pistons) =7,259mm^3 or 7.3cc of fluid.

and i do not car to show my math, but if delta T is 200f the increase in fluid volume (considering the calipers will expand too) would be under 0.5cc. so i guess that is not a huge deal, but still significant

now lets say that welded on res.(22mm OD) has an 18mm ID and is 40mm tall, (9mm^2 x 3.14) x 40mm = 10,174mm^3 or 10.2cc

if you rode that hellion, you would have about 3cc of fluid to spare, which equates to less than 0.5mm of pad wear. you would have check and top off you reservoir every every long ride.

f' that

Popeye the Sailor · January 17, 2009, 11:46:48 AM

We don't know average pad wear or the actual distance it actually needs to move to apply full stopping force, so without proper numbers, IMO, it's an exercise in futility. We need more to come up with a proper factor of safety.

TAftonomos · January 17, 2009, 01:04:33 PM

Quote from: aaronb on January 17, 2009, 10:26:48 AM
OK, this is the first time i have ever actually put numbers to this.... if you see an error, please feel free to correct me.

IIRC the pistons in most 4 pot MC calipers are 34mm each, lets say each piston needs to move 1mm to apply full stopping force...

(17mm^2 x 3.14) x 1mm x 8 (pistons) =7,259mm^3 or 7.3cc of fluid.

and i do not car to show my math, but if delta T is 200f the increase in fluid volume (considering the calipers will expand too) would be under 0.5cc. so i guess that is not a huge deal, but still significant

now lets say that welded on res.(22mm OD) has an 18mm ID and is 40mm tall, (9mm^2 x 3.14) x 40mm = 10,174mm^3 or 10.2cc

if you rode that hellion, you would have about 3cc of fluid to spare, which equates to less than 0.5mm of pad wear. you would have check and top off you reservoir every every long ride.

f' that

Not bad, buy you forgot the fluid that is in the caliper(s), the lines, and inside the bore of the master. The reservoir is there for some expansion, thats all really.

Capo · January 17, 2009, 01:44:08 PM

Quote from: MrIncredible on January 17, 2009, 11:46:48 AM
We don't know average pad wear or the actual distance it actually needs to move to apply full stopping force, so without proper numbers, IMO, it's an exercise in futility. We need more to come up with a proper factor of safety.

The brake manufacturers allready did, and sized their reservoirs acordingly.

Capo · January 17, 2009, 01:48:25 PM

Quote from: TAftonomos on January 17, 2009, 01:04:33 PM
Not bad, buy you forgot the fluid that is in the caliper(s), the lines, and inside the bore of the master. The reservoir is there for some expansion, thats all really.

What aaronb has quatified is the working volume, ie the volume that would leave and return to the reservoir on each application of the brake. The total volume of the system has no bearing on this.

aaronb · January 18, 2009, 04:45:26 PM

Quote from: Capo on January 17, 2009, 01:48:25 PM
What aaronb has quatified is the working volume, ie the volume that would leave and return to the reservoir on each application of the brake. The total volume of the system has no bearing on this.

no no, i make the beast with two backsed that up (I was hung over, sorry

). I know, the second the lever is pulled the orifice between the reservoir and master cylinder is closed. so yes, while 7.2cc may be need, that fluid is already in the system.

i have shamed my family.

Pasta Bobber · January 19, 2009, 07:19:49 AM

Ok, I've decided to use my bars as the reservoir. The I.D. is 7/16 and the area for the fluid will be no less than about 7 inches wide, which should give me more than enough fluid for both clutch and front brake. I've obtained a diaphragm and cap that I'll hide nicely. My next question is if DOT 5 fluid will corrode mild steel? I can build another set of bars out of aluminum or stainless, but we allready made a set in mild steel that I love.

TAftonomos · January 19, 2009, 10:37:13 AM

As long as the bar is above the master, that ought to be cool. If it's isn't, it ain't gonna work.

scott_araujo · January 20, 2009, 10:52:08 PM

I remember seeing a set of cruiser levers with reservoirs integrated into the grips or the lever mount. Switches for all the usual controls too. Very low profile and pretty pricey but amazingly clean. I'm not sure they'd have the volume to move a Dual front Brembo but worth a look. Now if I can only find the link...

Scott

Found it:
https://www.phatperformanceparts.com/ProductDetails.asp?ProductCode=BDL-HANDCONTROLS

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Stupid Reservoir Idea