12volt car starter controller for jet engine starter...how to??!

[jettoymaker]

Hi all,

It needs to be said up front...I and my collegues are unlearned in the science of electronics (but we are willing to learn faster) and we have a question to anyone willing to assist in our project.

We are currently constructing our latest prototype of a Gas Turbine powered motorcycle (see You Tube URL YouTube - having fun with John Wallis jet bike) and we have upgraded to a larger and more unique design of our own which unfortunately needs a much stronger starter associated. The leaf blower no longer does it for us

We need to produce at least 1 ft/lb of stall torque to begin rotation and we require a self sustain rpm of 12-15000rpm. This starter has to be 12volt. We understand that a series wound reduction gear starter (motor only) will do the job for the 20-30 second of starter operation to self sustain interval, but we need a ramp up facility and rpm control aspect included, so, we would like to know if there is a motor controller out there that doesn't cost the Earth and that is basically a plug and play senario, as we really have no experience in this field?

Alternately; is there a motor out there that will do the job instead of the starter, that has a comparable controller and won't suck our batteries dry and blow the hell out of itself?

Looking forward to a reply on this one.

 

[ronv]

Did you really mean 12 to 15 RPM?

 

[Diver300]

1 ft/lb seems a lot for winding up a gas turbine. I would have thought that you would need a lot less than that unless there is a lot of friction. 1 ft/lb at 12000 rpm is about 3 hp, which means around 200 A from 12 V. I know that your specification doesn't stay that you need both 12000 rpm and 1 ft/lb at the same time.

A car starter motor without the reduction gear might work, but controllers for that amount of power are expensive.

 

[tcmtech]

The little high reduction starter on my Mazda stripped out and I would say that its motor hits well over 12000 RPM free wheeling now but still wont fly apart. (I tried, really I did but no luck it just sits and screams!)

I would think taking most any small vehicle starter and setting it up as a direct drive without the internal gear reduction would probably work. Those small starter motors don't produce a lot of torque but make up for it with loads of speed.

As far as controlling their speed all they need is a simple PWM circuit driving a large multi hundred amp IGBT or set of smaller ones. A common 555 based PWM circuit and a large IGBT would likely be more than adequate as a control system.

 

[bobledoux]

The cheapest way might use stacked battery cells with a switching posts:

Assume the battery consists of six independent two volt cells wired in series. You could switch them in down the line starting at 2 volts, then 4 volts, then 6 volts until all 12 volts are providing power.

 

[jettoymaker]

Hi all,

Thanks for the very rapid thoughts on our problem...nice to see that the electrical sciences reflect the same dedication and facination that the engineering crowd play at

In answer to ronv - yes the rpm needed is 12-15000. Self sustain on these is a *****. We have also considered the stacked cells, but will have to get to grips with the machinery of the circuits and controls involved.

As for the 555 and associated PWM and IGBT...as soon as my tiny brain can assimilate the information, I would like to discuss their further use..but at the moment, my ability to comprehend them would be something akin to explaining the ease of using a typewriter to someone straight out of the jungle...all very alien and inexplicable

We tested the Toyota Camry starter we have and found it rotated to 20,000rpm unloaded, so at least we have an rpm we may use (and it didn't explode!!). The 200 amp 3 hp figures will be very good if we can get the rest of the system to play ball and survive. We assume that the 1 ft/lb figure will be static, but the likelyhood is that as windage increases with rpm, the load may go up. That's R&D I suppose...

All looking good so far.

Many regards

 

[ronv]

If your handy a hand full of 60 amp fets would drive it. If not might check out some robotic sites for low voltage high current pwms.