Vídeo que mostra vela acesa dentro do motor em fincionamento

[Alexpar Perfil]

O vídeo da traxxas mostra o reflexo da vela acesa na superfície interna polida da camisa e na cabeça do pistão.

Percebam que ela só se acende quando o pistão gira, pois o starter alimenta a vela e o motor de partida juntos.

Não há explosão ou combustão alguma, é só o efeito do reflexo.

Tem informação sobre como funciona a vela aqui:

/viewtopic.php?t=7240&highlight=rea%E7%E3o

Prá começar a explosão do combustível ela precisa ser aquecida. Quando se retira o glow ocorre uma reação "catalítica" da platina existente no filamento da vela com o metanol, que garante a continuidade da reação. Agora, se esta reação mantém a vela incandescendo, talvez só um engenheiro químico possa responder.

[mach]

Será que no motor GLOW funciona do mesmo jeito de um a DIESEL?
Pois no motor a diesel temos a vela somente para esquentar o combustível para dar o "start", a partir daí devido a alta compressão o diesel explode expontaneamente, seria a mesma coisa no glow.

[Alexpar Perfil]

Negativo!

A compressão faz parte do processo mas não é como diesel.

Já aconteceu várias vezes da vela estar incandescendo mas no carro não vai. Isto é porque a platina do filamento da vela não dá mais reação com o metanol.

No carro a diesel se a bateria arrear você engata o carro em outro e o faz pegar no tranco, ou seja, a resistência de aquecimento não é essencial.

Agora, tenta fazer pegar motor do carrinho sem o glow.....

[Bettini Perfil]

A vela no motor glow tem a função de manter o combustível em uma temperatura suficiente para que haja a combustão, ou seja, a vela aquece o combustível e não deixa a combustão parar. Por isso, por exemplo, usamos velas quentes no inverno e velas frias no verão. Mas em hipótese alguma a vela gera a faísca para combustão!

Só tô dando o pitaco, pois estudo Egenharia Mecânica e conheço o funcionameno do bichinho.

[Alexpar Perfil]

VAMOS PARAR DE FALAR BESTEIRA E PESQUISAR!!

LEIA EM:

http://www.rchobbies.org/cars_eng-tuning.htm

ISTO:

GLOW PLUG
A glow plug’s temperature range is critical to proper performance. Small-block engines generally use warm to hot glow plugs, while big-block engines use plugs in the colder range. If you choose a plug in the wrong temperature range, you could be chasing the tune of your engine till the sun goes down. Changes of the relative temperature of the glow plug can be beneficial, however.

A combination of compression, heat and a catalytic reaction between the platinum in the glow-plug coil and the methanol in the fuel creates combustion in a nitro engine. Altering the heat range of your glow plug can alter the timing of the combustion process. Nitro engines don’t have an ignition system that can be used to advance or retard combustion timing, but a hotter plug that causes ignition a little earlier in the combustion process can have the same effect. “Advancing” the ignition timing can increase overall power output, especially at higher rpm. There are limits, however, and installing too hot a plug causes pre-ignition (detonation) and risks damaging your engine.

It’s a challenge to figure out a glow plug’s temperature range. Manufacturers don’t use a consistent and universal standard to rate the temperature ranges of their glow plugs. You will probably know the temperature of a plug relative to others within a given product line, but currently, no rating system allows comparisons among manufacturers. Here again, plain old experience with a variety of glow plugs will help you to know which are best for the effect you want.

...



E EM:

http://www.bsrcc.com/glowplugs.htm

ISTO:

How Does A Glow Plug Work?

Contrary to what many have previously been lead to believe the following is an explanation of how a glow plugfunctions in a motor. The plug is initially heated by applying a voltage (typically 1.5 volts) to it.
This is to cause it to glow so as to ignite the fuel at compression and start the internal combustion cycle.

Once the cycle has started, the power source can be disconnected, as with the heat generated at combustion the CATALYTIC Reaction generated between the methanol and platinum in the plug coils becomes sufficient to keep the process going. The catalytic reaction is a reaction whereby platinum will glow in the presence of methyl alcohol vapour. This will happen without any external power source being applied.

How do you select the correct PLUG for your application, and why ?

To do this you need to understand a little more of the theory behind the process. In glow fuel the catalytic reaction is generated between the methanol and platinum only. Castor oil, synthetic oil, nitro methane,
etc do not generate a catalytic reaction with the platinum.

Next you need to understand that a certain surface area of platinum is required to generate a sufficient catalytic reaction to keep the internal combustion process going. Also it is necessary to allow extra surface area for the reaction to be great enough when it diminishes with the available methanol dropping as in the case at motor idle. Simply put, cold plugs are manufactured using a thicker wire to give greater surface area to facilitate a greater reaction and thus the required catalytic reaction where less methanol is present in the fuel mixture.

So! More nitro means less methanol which in turn means a greater surface area to platinum will be required to generate a sufficient catalytic reaction. Suddenly it all makes sense! To work out which temperature plug to use, you need to know how much methanol is in your fuel, not how much nitro or oil.

As a rough rule of thumb;

80% methanol or above, use a hot plug.

70%-75% use a medium plug.

60%-75% use a cold plug.

65% or less use a very cold plug.

Idle Bars and Other Stuff

Again, contrary to what many believe, the idle bar on a glow plug is not necessarily what its name would
suggest. It is in fact to stop any fuel not vapourised from dousing the platinum coil of the glow plug by
dispersing it away from the coil.

Why are plated coils not as good as platinum alloy coils?

Plated coils suffer from very quick degeneration as the plating breaks down under operating conditions.
As bits of plating come off, the plug is effectively becoming a hotter and hotter unit until in a comparatively short time it is no longer able to perform its function. Conversely, a platinum alloy coil will still degenerate, but as it is platinum alloy throughout, the surface remains as platinum alloy and the plug continues giving much the same characteristics for quite a long time.

Plated coils are very poor value when compared to platinum alloy coiled glow plugs.

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Se for difícil para ler em inglês, jogue no tradutor do google.

Boa Sorte!

[opan21 Perfil]

E esse ultimo vídeo, postado é de um motor de carro 1/1 e possui centelha. Acho que há alguma dificuldade em fazer o vídeo do motor glow. Mas se tiver um por aí coloquem aí. Valeu!