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Author Topic: APS/Ω Gas turbine bike build  (Read 489475 times)
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wobblywalrus
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« Reply #30 on: March 27, 2013, 11:07:35 PM »

Sometimes it is a good idea to have some gussets and bracing to give the chassis some redundancy.  In other words, there is more than one weld holding together all of the vital stuff.  My Triumph is set up that way.  It is extra work but worth it for the "peace of mind" you will get when going fast on a bumpy track.     
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Mobacken Racing
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« Reply #31 on: March 28, 2013, 12:25:43 AM »

Thanks for the clarification, the tig welds look good and I am using the right filler rod so I am confident that they are strong enough. The frame will get more braces at the weak points later and I will add steel plates where the frame tubes meets the steering head as an extra safety.

I´ve been told to avoid putting too much heat into CrMo so I have been careful while welding.

Good to hear this so I won´t be anxious about the tech inspection, in drag racing you aren´t allowed to paint a CrMo frame so I thought the same rule applied here but then it would start to rust in no time in the salt. sad
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DND
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« Reply #32 on: March 28, 2013, 01:55:14 AM »

In the early drag racing days a fellow i knew bought a pro built top fuel car and the frame was gas welded with way too much heat.

He got into to a side wind in the finish line light's and it rolled and came all apart, and he lost his life.

The welds held but the parent metal next to the welds all split and came apart from the way to hot welding joints.

That is why it is good to have a pro look at your stuff , so you know inside that your welding is OK for future work.

You don't want to wait for cracks to show up , that is not good at all because if it gets welded together properly they should never crack.

Don
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Mobacken Racing
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« Reply #33 on: March 28, 2013, 04:03:14 PM »

I´ve heard stories about CrMo cracking just outside welds, shows how important it is to know the material well.

About another thing, just how much of the bike will be subjected to salt spray during a run? I guess it depends on how wet the salt is, so lets say in the worst possible conditions. I use the LSR5 front fender from Airtech by the way.

It is vital that no salt will reach the nose section of the fairings since the engine intake will be there, I cannot filter the air in any way since there isn´t anywhere near as much room as a non-restricting air filter would need. The engine consumes 1m3/s and even the smallest restriction in the air flow will cause overheating and possible engine damage.

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saltwheels262
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« Reply #34 on: March 28, 2013, 06:15:34 PM »

the salt is going to get in places you didn't even know you had.
it will be everywhere. it's in the air.

keep the intakes plugged until you run.

it's been going on for over 60 years and the mill will survive.
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bub '07 - 140.293 a/pg   120" crate street mill  
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manta22
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« Reply #35 on: March 28, 2013, 06:54:19 PM »

Anders;

Most race car and aircraft builders who use chrome- moly tubing use it in "Condition N", normalized. The weldment doesn't need to be heat- treated if it is welded properly. Gas welding spreads the heat over a wider area so the joint has less built- in stress than a TIG weld. TIG is fine, though, if it is carefully done.

That's an interesting project you have there.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
Crackerman
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« Reply #36 on: March 28, 2013, 09:41:07 PM »

Dont be afraid to weld, cut, break a few test coupons. It will tell you alot about the condition you leave a weld joint. If the parent metal lets go, or the weld does.
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Mobacken Racing
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« Reply #37 on: March 29, 2013, 03:17:00 AM »

the salt is going to get in places you didn't even know you had.
it will be everywhere. it's in the air.

keep the intakes plugged until you run.

it's been going on for over 60 years and the mill will survive.

Ok, so it is like fine dust blowing around?

What about during the run, some turbo vehicles run filterless with the intake high up in front. Are they still ingesting salt or is the air there free from particles? The compressor would show signs of wear on the inducer edges very soon if salt is present in the air.
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Mobacken Racing
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« Reply #38 on: March 29, 2013, 03:20:46 AM »

Anders;

Most race car and aircraft builders who use chrome- moly tubing use it in "Condition N", normalized. The weldment doesn't need to be heat- treated if it is welded properly. Gas welding spreads the heat over a wider area so the joint has less built- in stress than a TIG weld. TIG is fine, though, if it is carefully done.

That's an interesting project you have there.

Regards, Neil  Tucson, AZ

Early CrMo dragrace frames were soldered and that seems to work as well, I´ll show the frame to my frame building friend and stop worrying about it.

Thanks! smiley
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Mobacken Racing
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« Reply #39 on: March 29, 2013, 03:21:44 AM »

Dont be afraid to weld, cut, break a few test coupons. It will tell you alot about the condition you leave a weld joint. If the parent metal lets go, or the weld does.

That is a good idea, never hurts to do some tests to see how much heat is needed to weaken the surrounding metal.
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manta22
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« Reply #40 on: March 29, 2013, 10:47:07 AM »

"Early CrMo dragrace frames were soldered and that seems to work as well, I´ll show the frame to my frame building friend and stop worrying about it. "

Anders;

I think you might mean "Brazed"....ordinary lead/tin soft solder is nowhere near strong enough for structures.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
Mobacken Racing
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« Reply #41 on: March 29, 2013, 12:56:06 PM »

"Early CrMo dragrace frames were soldered and that seems to work as well, I´ll show the frame to my frame building friend and stop worrying about it. "

Anders;

I think you might mean "Brazed"....ordinary lead/tin soft solder is nowhere near strong enough for structures.

Regards, Neil  Tucson, AZ


Hi Neil,

Of course, here in Sweden we call it hard soldering so I simply used the wrong word.
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maj
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« Reply #42 on: March 29, 2013, 03:04:02 PM »

Part of the international flavor of this group, we get to know all the different words and spellings

I find myself spelling things differently here than an Australian forum

The salt is often slightly damp, but with a sometimes dusty surface , depending on traffic etc

we get very little salt in the bikes with front air intake , much less than the turbo with low intake and filter
 but still see signs of minor tip wear over over a couple of yrs, not sure if the foam rubber seal at the turbo intake is 100% either
potentially this is more of an issue than front air with a good front fender   
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Crackerman
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« Reply #43 on: March 29, 2013, 03:39:46 PM »

I thought the grain structure was too tight to properly braze, weakening the parent metal dramatically, making it very brittle? Or an I thinking of the wrong metal?
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manta22
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« Reply #44 on: March 29, 2013, 03:41:59 PM »

No, you are right-- brazing chrome-moly is not recommended. It reduces its fatigue life. I read a study of that by Lockheed years ago. It is just fine for mild steel, though.

Regards, Neil  Tucson, AZ
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Regards, Neil  Tucson, AZ
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