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Old 05-19-2022, 04:46 AM
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invertmast
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Originally Posted by SAP_2000
I am having the same issue with my Baja 2.6 meter L-39
Thread here: BajaHobby L39

I get good braking force at stand still and up to around 15 mph, but zero (and i mean zero) braking force above that.
I seems JP have several different brake designs on their wheels. The smaller wheels has the common design with a brake disc between the "drum" and the wheel, wile the bigger wheels (i have 95mm JP wheels and brakes) have a design with 4 metal plates held by magnets to the inside of the wheel.

The faster the wheel is turning, the stronger the sentrifugal forces are and i have a feeling that at landing speeds, lets say 50 mph the sentrifugal forces are too great for the magnet to overcome and that why you get no braking force when u really need it at high speeds.

I did some calculations. @ 50 mph, my 95mm wheels will have around 800 G at the outer edge of the tire. The brake pads sit about 2 cm further towards the axle, so lets say they get about 500 G´s of sentrifugal force that the electro magnet would have to overcome before start have a braking effect. I feel the problem lies in the design of these brakes more then in the controller.

I been emailing JP europe, asking if any changes to the brake design and informing them i just want to buy brakes (or wheels and brakes) that actually works, but I have gotten very vague answers to direct questions about what is different and even if the design is the same or not. Makes it kind of hard to decide if order new brakes/ wheels or not when not get a clear answer if they are the same poor design or not.

So my question is if anyone gotten the JP braked with the 4 metal plates to work well at high (landing) speeds, and if so how?

JP smaller wheels brake design. A more common and well working design IMO

JP bigger wheels brakes design. The 4 metal plates experience huge sentrifugal force as they are attached to the inner side of the rim on the rotating wheel. Did anyone get these brakes to work well at high speeds?

JP big wheel brake drum. Notice the small surface area to create friction for metal plates in the wheel

4 metal plates are held in place with 4 small magnets in the rim

brake plates removed. These plates would have to overcome a sentrifugal force of around 500 G @ 50 mph before even touching the brake drum.

Sentrifugal loads on the wheel at a given speed. The brake plates sit about 2 cm in towards the axle, so lets say 500G

based off your pictures of the bigwheel brakes, the lack of breaking is because of the lack of surface area between the wheel pads and the brake drum.

if you were to fill in the area on the brake drums between the metal area’s with an epoxy so as the entire drum surface is flat, i bet the breaking action would improve greatly. If you could find some sort of thin break liner (maybe some DIY gasket maker material or flat O-ring) you could probly make them work amazingly well.
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SAP_2000 (05-19-2022)