# Calculation -- Torque to slow down heavy spinning reel

1. Jun 26, 2014

### JST2014

I am designing a brake system for big reel that weighs about 2500lb, spinning down on a truck that is moving at 15mph, the shaft is 2.5inch in diameter. It is rotating at 53RPM and it comes to a stop at about 45 seconds.

How do i start performing calculations and the design parameters?

Thanks

2. Jun 28, 2014

### Lok

Hi JST2014! and welcome to PF.

A reel diameter would be nice!. I will suppose a 3m diameter for most of my post.

You will need to know how much energy is in the spinning reel which will tell you what force and disk diameter to choose.

Before all, I am wondering why can you not use a normal car disk brake system (used car lot). A normal car weights around 3200lbs and can stop from 40 - 0 mph in around 10 s (a gentle brake). The disk will need an adapter for your shaft and the caliper a support. The rest will work nicely and considering the low cost of already made parts you can always slap on two disks if the necessity arises.

You can work out the energy by using 1/2*mv^2, just that v=2*pi*Radius*RPM/60 (where the radius is the distance from the center of gravity of a slice of the reel (usually looks like a rectangle) to the axis of rotation.
The energy/time will give you the power necessary to be absorbed by the braking system and will go on to determine the other factors which are overly complicated. Honestly the setup seems slow and low on energy and one car break should be more than adequate.

3. Jun 28, 2014

### JST2014

Hey Lok, thanks for the swift reply.

The reel diameter is approximately 91.5inches in diameter. It can spin in a pretty fast manner when traveling down the road. The current design utilizes a drum brake and it takes up way to much time (given tight shaft tolerances) to assemble and disassemble, i am thinking of having a quick assembly.

One quick question, is there a way i can obtain the pressure that is needed (if some sort of hydraulic air system is used) to stop the reel from rotation?

4. Jun 29, 2014

### Lok

For the first issue of assem/disassem could you just place the brake on a separate shaft and connect the two shafts by an easy to disconnect chain drive?

The second has no simple answers. I estimated a few values and simplified a few formulas in an excel file and clearly did not know about the upload any file capability of PF, so I made a JPG also.

This would be the broad and distant picture about your braking necessities. For more I would recommend seeking a Book about designing a breaking system. And after 2 weeks of hardcore computations you will have a running system idea that might not apply from a spatial point of view :P

Edit: I forgot to put the coefficient of friction between steel/steel for the Friction force. It is around 0.8 so the Normal force (and pressure) needs to be 1.25 higher to achieve the same effect.

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Last edited: Jun 29, 2014