[GP250] KTM 250

Toop a écrit:

Thanks Frits, any crankshaft of this sheet ?

No pictures of the crankshaft, but nevertheless a little more information: in contrast to the usual 180° firing order of a parallel twin, the KTM GP250 has a 90° / 270° firing order, making the balance shaft indispensable.

MANETON a écrit:

Je suis surpris de l'utilisation de thermocouple type J ou K. J'ai toujours eu l'impression, peut-être erronée, qu'ils n'étaient parmi les plus réactifs. A moins que ça ne provienne des caractéristiques de la sonde ou du traitement du signal.

J- and K-thermocouples are quite fast, but the response time of most industrial thermocouples is severely impaired by their shielding.
The actual thermocouple, consisting of two dissimilar electrical conductors forming an electrical junction, is embedded in ceramic and additionally packed in a stainless steel sleeve.
Without all this shielding, a thermocouple can respond a hundred times faster to temperature changes. That is why I make open-junction  K-thermocouples myself, using a bobbin of chromel wire and a bobbin of alumel wire.
The wires can be joined with silver brazing or with spotwelding, using a capacitor discharge in the same way that we make ignition glow plugs.
Without the shielding of industrial thermocouples, homemade thermocouples do not have eternal life, but that is more than made up for by their fast response time. And it is not that difficult and not that expensive to make them yourself.

Frits Overmars a écrit:

Toop a écrit:

Thanks Frits, any crankshaft of this sheet ?

No pictures of the crankshaft, but nevertheless a little more information: in contrast to the usual 180° firing order of a parallel twin, the KTM GP250 has a 90° / 270° firing order, making the balance shaft indispensable.

Hello,
Thanks for the infos!
I understand that, but with a 180° crank their still is a secondary order imbalance no?
I dont know the length of the rod and the stroke, but since it must rev hight, they may not be negligible?

thanks frits

Hello,

Frits will stop at nothing!

Francis.

Frits Overmars a écrit:

No pictures of the crankshaft, but nevertheless a little more information: in contrast to the usual 180° firing order of a parallel twin, the KTM GP250 has a 90° / 270° firing order, making the balance shaft indispensable.

Oupsssss
Here is a surprise, I have to do some simulations and think if I want to integrate this notion, I did not expect that, surprising ....

Thanks.

Joli sujet qui redémarre bien après une longue réanimation depuis le 1 er Oct 2010 et avec peu de séquelles .

Merci Frits pour ce partage d'expérience, ce n'est donc probablement qu'une impression ou un "retard" provenant des matériels de mesure en comparaison des thermistances.
Pour ma part, quand c'est possible, pour les thermocouples, je conserve aussi les soudures à l'air libre ou simplement les fils "twisted". Sinon, pour certaines applications, nous obtenons de bons résultats avec un "enrobage" laiton.

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Pas grand chose pour le moment...

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fpayart a écrit:

Frits will stop at nothing!
Francis.

I was going to say the same about you Francis

Salut Marc,

merci pour les photos supplémentaires.

pipoff