TELMA RETARDER

[terry allen]

HI I got a telma retarder it is a in the propshaft one, not on the gearbox type i am going to fit it to the rolling road dyno i am building has any one used a telma any thing to look out for ect i have not got a clue how i am going to control it but it wos free to a good home with all the control bits of the bus it wos fitted on cheers Terry

[FPV_GTp]

[bruce]

I have a KLAM retarder I'm setting up as a steady state engine dyno. My dyno project is kinda on hold as the flowbench project took over . . .

[FPV_GTp]

http://www.land-and-sea.com/eddy-current-dynamometer/eddy-current-dynamometer.htm

Always wanted to make a small eddy_current retarder just for experimental purposes

like the palm held unit from land&sea dynos , utilizing a car disc rotors and starter motor solenoids for the magnetic coils windings section of the retarder. Using a differential axle and housing tube and bearing ends. All this material is just floating around the workshop wouldn't have to invest any money into it just time.

Q. What is better to have High voltage and low current ? OR Low voltage and High current ? to create a magnetic field ?

cheers

[terry allen]

hi good pictures where did you find the ones with the retarder mounted i would like to get a better look at them cheers

[FPV_GTp]

Hi terry allen, will have a look in my favourites sections and find the website and post a link

might take a few days as I have heaps saved in my favourites folder

cheers

[FPV_GTp]

Get on ebay

there are few superflow items

1. SuperFlow SF-1810 Eddy Current Power Supply
2. SuperFlow SF-1808 Throttle Control, Powers Up
3. Lot 4 SuperFlow 1200A-1219/1200A-1073 Rev A Boards
4.SuperFlow Autodyn Chassis Dyno 740 Inputs rack mount
5.Lot 2 SuperFlow 1200A-0956 ASSY 500 Rev A Boards, New
6.SuperFlow Rack Mount Universal Input 15 pin cabl Used
7.Lot of 4 SuperFlow 1002 Central Processing Units, Parts
etc

[jsa]

[FPV_GTp]

http://www.youtube.com/watch?v=u9_NWz30deo

[FPV_GTp]

http://www.autospeed.com/cms/A_1646/printArticle.html

[FPV_GTp]

http://www.theoldone.com/articles/Dyno_Room/building_a_dyno_roomfinal.htm

[Tony]

John has nailed it.

Designing a retarder is a bit tricky, because there are a number of conflicting requirements that need to be balanced.

As John says, amps x turns determines magnetic field strength. But all those amps and turns will generate a lot of electrical heating within the winding. The external surface area of the winding determines how well it will cool, and how hot the wire will actually get inside the coil. It is very easy to burn up these dyno coils with too much dc current.

There will always be an even number of windings, whatever will fit around your particular rotors. Four, six or eight windings are fairly common. But it could be any even number. The windings can all be made identical, but the electrical connections should alternate between adjacent windings. So each pole face alternates, north, south, north, south, and so on around the rotor.

The multiple windings can be connected in various series or parallel combinations depending on the required final operating voltage.

A typical Telma retarder has sixteen twelve volt windings. If they are all connected in parallel this will run off a twelve volt vehicle electrical system. If two parallel strings of eight are connected in series, it will then operate from a twenty four volt system quite common in trucks.

Other coil connection combinations are possible, and if all sixteen windings are connected in series, a Telma can be run from a 12 x 16 = 192 volt dc supply if you have that high a voltage.

I have a friend that owns a transformer winding company, and at one stage he was asked by a customer to rewind some dyno retarder coils that had burned out. He gave me all the details of how he stripped the burned out windings and counted the turns, and measured everything up.

The central iron magnetic core was 80mm in diameter and 90mm long (face to face). The coil consisted of 380 turns of 2.0mm diameter copper wire. Outside diameter of this coil 125mm. This is a twelve volt coil, the electrical resistance ends up being around 0.695 ohms, and it draws 17 amps at 12 volts. This is for a fairly large retarder. Sixteen of these coils will hold 900 Ft/Lb of torque at 4,000 rpm (685 Hp)

I don't know if that helps anyone, but it is a starting point for anyone planning to reverse engineer the coils of a fairly large eddy current retarder.

[FPV_GTp]

Tony , that's nice little bit of information , by chance were the retarders that you friend rewind small single Mark-1 Heenan and froude eddy current dynamometers ?

cheers

[Tony]

All I know is that they were off some sort of Telma eddy current retarder. My friend was only given the sixteen burned out coils to rewind, he never saw the actual retarder itself.
I looked up some specifications of various Telma models, and these coils appear (?) to be from a model CC125, but that may not be correct.

The important thing is the wire size, number of turns, and the iron magnetic cross sectional area. From that it should be possible to calculate a few things, and adapt the design to suit something different.

My own Telma is much smaller than this, it is a CC80. But I am unlikely to pull it apart and measure it all up, unless it blows up. Each of my coils are quite a bit smaller, and only draw ten amps each.

[FPV_GTp]

Homemade Coil Winding Jig http://www.youtube.com/watch?v=yN3heVGEEZc