Partial charge with an alternator ???

[Pierre-Yves]

a friend of mine wants to take measurements on a diesel engine of 305 scrapped and put on a bench. He installed water doping.

To simulate partial loads, he plans to connect resistors to his alternator (an electric or hydraulic brake is expensive).

I'm puzzled: how far can we go with the original alternator? Wouldn't it be better to use a truck alternator? something else ?

[Chatham]

this does not lead to anything, with an alternator, even in a truck, the engine load will be ridiculously low, moreover the alternator belt transmission would never collect more torque, unless you make quadruple pulleys with industrial V-belts ...

[Flytox]

Bonjour à tous

Indeed with an original alternator which is (in the 400 w?) We are far from the power supplied by the engine.

To make an "economic" bench and at "self-regulating speed", if you have kept the gearbox and axle clutch of the vehicle, you can always turn a large propeller coupled to a gearbox outlet. The other gearbox output is blocked, the differential therefore significantly increases the speed of the shaft used as drive output.

Propellers can be used like those found on some cooling towers (3 to 5 blades in diameters 700 mm). We can put several on the same tree to be in the power range sought.

For the absorbed power it works as a cube of speed. If the gearbox ratio is well chosen, and the number of propeller to be rotated also there is no risk of over speed and engine breakage. This regulation also does not block the engine suddenly. To estimate the power (by comparison), simply measure the speed (of the constant ratio engine) or that of the propellers and correct as a function of temperature and atmospheric pressure.

The downside is a (rather violent) draft to channel outside the work area and the noise ... which is also mind-blowing
Finally noise can be isolated and all this remains within the reach of a handyman.

[Pierre-Yves]

Thank you Chatam and Flytox. I now have arguments against this approach. The boyfriend in question was so certain that I had come to doubt it!

The engine no longer has its gearbox. I think it will be difficult to prove anything in this configuration.

[Christophe]

Load an engine with its own alternator?

It would not be the kind of experience made by people who want to show that it does not work ...

Otherwise there is always a way to tinker with a generator with a recovery alternator but it's a job and you have to make it run at 1500 rpm ... not obvious with a car regulator ...

The most economical would still be to buy a Chinese group ...

[elephant]

These tests do not make much sense. A load of 30 to 40 kW should be available, i.e. 60 halogen lamps, 15 radiators ...
to simulate a car at 90 km / h, fighting against the wind!

[Christophe]

A car alternator could be used to charge ... a SOLEX engine ... but that's it

Tomorrow I will post an article on the power required in relation to the speed, the SCx and the mass of a vehicle ...

It is in this document: https://www.econologie.com/les-transport ... es-27.html

But apparently nobody takes the trouble to read it so I will make it an article may be more visible.

Conclusions: a power of 15 CV is therefore sufficient in town for a particular vehicle whose overall mass does not exceed 500 kg. For a vehicle of 1000kg or more (in the case of delivery commercial vehicles for example) the power varies
linearly for our parameters set according to the equation:

Power at 50km / h = 0.0343xMass + 2.5313

The percentage of maximum power used in cities by cars currently on the market is therefore minimal: it varies from 10% to 20% depending on the power of the vehicle.

On average over the entire duration of the journey, counting the different stops, we descend far below 10%, the overpower of vehicles circulating in town generates overconsumption, pollution and congestion, in fact which says power says mass
so volume.

[Flytox]

Bonjour Christophe

Conclusions: a power of 15 CV is therefore sufficient in town for a particular vehicle whose overall mass does not exceed 500 kg. For a vehicle of 1000kg or more (in the case of delivery commercial vehicles for example) the power varies
linearly for our parameters set according to the equation:

Power at 50km / h = 0.0343xMass + 2.5313

Can you detail how you get there please?

[chatelot16]

if the goal is to make 15cv a car engine is ridiculously too big and can never have a good performance


to measure the performance of a running car engine you need a charge in the right power range: something that works well is a telma: electric truck retarder: it can eat a lot of power

[Flytox]

Hello Chatelot16

to measure the performance of a running car engine you need a charge in the right power range: something that works well is a telma: electric truck retarder: it can eat a lot of power

Indeed it can absorb a large "instant" power without problems ... for continuous use it will be necessary to adapt an additional cooling much more effective than the small original fan not to burn everything. Regarding the regulation of the speed or the power absorbed .... may not be so simple or so economical .... well there are some tips on the subject who may have ideas
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