Brakedrum Generator

Ed on bike
We built ten of these brakedrum generators. The way it is hooked up here - if we are not pedaling enough - then the necessary power is drawn from the batteries but the more efficient way, if you don't have to keep the power on, is to use the power directly and let any excess power being pedaled go into the batteries. You lose 20% of the power by storing it in the batteries first. It is always more efficient to use power directly - rather than converting it and then converting it back.

Not only will we use these generators on bicycles in the shelter but later we plan to use 8 of them for wind power and 2 for water power generation. We can't use wind and water power at the moment because the government won't allow us to. They say that wind power makes noise (I never got the chance to find out) and disturbs the neighbors and that water power would disturb the fish (Hah! They have killed most of them with winter salt from the highway, and agricultural sprays from the farms - long ago.)

What is described here are generators made by taking the brakedrums off of old either F-250 or F-350 Ford pickups or vans. Some others may work but these were for what we had plans. The brakedrums were used simply for outer casings to hold the magnets and to provide the bearings to revolve them around the stator. Other designs can be made out brake disks or out of wood. The latter may be a lot more simple - although not as durable.


Here is a close up of one of the assembled generators. Lining the inside of the brakedrum we have put 16 permanent magnets. The stator is in the middle and in operation is held steady while the brakedrum is revolved around it by the belt from the bicycle or the blades of the windmill, or the water wheel.

The post nuclear salvaging key to making these will be finding the stators and magnets. One will also have to find wire for the coils. My son and I were able to go to a metal scrap yard that literally had a mountain (about 20 feet high and fifty feet in diameter) of old motors. It was a hot summer day and we spent five hours going through the motors looking for ones with the right size stator. Once we learned what we were looking for we should have spent more hours or a couple of more days getting the right ones instead of, because of the heat, taking what we did and then later putting so much effort into making them fit.

Below is a picture of a stator (on the left) and a brakedrum (on the right).The stataor is what you have to dig out of the old motor casings. The difficulty is finding a stator the right diameter to fit into the brakedrum or other housing that you are building.

When you first get the stator it has copper wire all wrapped around it and through all those slots. You have to cut the wire (probably with a chisel although we used a cutting wheel) and then knock it out of the slots. The latter can be quite a task.


We were able to buy new magnets but new magnets will probably be hard to find after a nuclear war. We talked with many experts about this with the thought of making magnets. One idea that was suggested was crushing old magnets and then reforming the powder to the size that we need and then remagnetizing them. The best idea that we have at the moment is to simply take magnets out of old speakers and cut them into smaller workable squares or shapes and then assemble these into the shape needed. The magnet parts will adhere to each other and one could use some additional glue if they wanted to.

coil winding
I tied up for weeks a big chunk of my wife's kitchen counter and we spent many hours on each step along the way. Didn't take a picture at the time so we posed this one later to try to show the homemade coiler. In the background is also a base and former for holding the stator and pressing the coils down around it when one mounts them to the stator.

The books describing the process make it sound very easy once one has the parts but in actuality in building ten of these generators we found that there was a substantial learning curve.

After the war, finding wire to make the coils may also be a problem - but old coils can be unwound. So all this is doable.


Here I am with the lathe that I used for many, many hours to turn down the stators and brakedrums so that the two would fit together. We should have been more selective in matching stators and brakedrums.

Most people won't have a brakedrum lathe but since we were doing so many we got this one rather than paying someone else to turn the brakedrums for us.One doesn't have to use a brakedrum. A housing may be just turned out of wood and one doesn't have to have a lathe - because they can use as a lathe the rear hub of a rear drive car if they need one. This whole design was made originally for use in rural areas of Third World Countries where they would have practically no tools available.

The basic concept is that the magnets are mounted around the inside of the brakedrum. In fact, glued in place there. The stator is then mounted inside the brakedrum and held stationary so that the brakedrum and magnets revolve around the stator when the brakedrum is turned by the bicycle, windmill blades or a waterwheel.

The big problem is getting the stator with its coils mounted on the outside of it to fit inside the brakedrum with the magnets mounted in a circle around it on the inside of the brakedrum. One needs a small gap (the smaller the better) - but there needs to be some gap so that if there is wobble or anything the coil wires won't rub against the magnets and wear off the insulation from the coil wire.

All the details for coil winding are available on this website and you will find them, for example, in the .pdf file dealing with wooden generators. The details for the coils remain the same so rather than being redundant I am not covering them here.


All the details for making generators from brakedrums was available from Bob Budd and I had to consult with him many times. He is on the left and with him are my son, and neighbor - an experienced wheelwright. I also had the help of many others, including several expert mechanics and machine builders.

There are two versions of brakedrum specifications. One comes from the UK and the other from the US (actually I got them from Bob Budd in Canada).

Here are some basic dimensions for the two versions.
There are diagrams below to help you identify what the dimensions mean.


UK version

N. American







Transit van

Ford 3/4 ton truck



(long wheelbase)

E or F 250 or 350


Internal diameter

254mm [10"]

306mm [12"]


number of magnets




Magnet length

64mm [2.5"]

76mm [3"]



32mm [1.25"]

51mm [2"]



20mm [3/4"]

25mm [1"]


Air gap diameter

212mm [8 5/16"]

251mm [9 7/8"]


lamination diameter 

204mm [8"]

245mm [9 5/8"]



64mm [2.5"]

76mm [3""]






Coil former leg length

76mm [3"]

76mm [3"]


overall length

96mm [3.75"]

90mm [3.5"]



22mm [7/8"]

33mm [1 9/32"]



2.5mm [3/32"]

2.5mm [3/32"]


no. coils/ phase & total

10 & 30

8 & 24


Wire size

0.8mm diameter

0.7mm diameter






wire turns per coil




nominal voltage delta













Other arts involved are those of making propeller blades and vanes for wind generators and water driven devices of some sort for those that are used with waterpower. These are separate issues that I cover on their individual specific pages.

Rather than each individual trying to build their own - I would recommend that a group of skilled mechanics specialize in the art. In fact in a shop they could create sub-specialties. Coil winding and magnet assembly being but two examples.

I would not call learning to build these devices trivial. All the information is here but people many times asked me why we didn't just go out and buy one - because it would have been many times cheaper. However, our purpose was to learn this technology so that we could communicate it to others in a time when they will have to build their own.

Those inclined to study the art ahead of time will do well to visit brakedrum Details: Hugh Piggott's Website or brakedrum Details: Bob Budd's Website

Hugh and Bob are the main designers of these brakedrum systems and you can get details from them on how to do it. Bob puts out an excellent video that I have bought and watched dozens of times. It would be a great thing to have.