10/23 Raptor Video

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wsimpso1

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What type of seals were in the original steel housing?
I have not watched enough of the videos that closely to be sure. My impression is that the sleeve is only sealed by the close radial fit. Could be wrong... A close radial fit exposes the assembly to seizing and galling that seemed to be shown during a recent video. I do know that with rotating seals, a close fit is not needed, but centering bearings are needed to then make that reliable.
 

BBerson

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I have not watched enough of the videos that closely to be sure. My impression is that the sleeve is only sealed by the close radial fit. Could be wrong... A close radial fit exposes the assembly to seizing and galling that seemed to be shown during a recent video. I do know that with rotating seals, a close fit is not needed, but centering bearings are needed to then make that reliable.
I was thinking his existing shaft should be polished and the collar honed. That might give it the correct clearance if lucky. Someone on the video has commented he should make the collar with special bearing bronze. I don't think the collar has much bearing load. It just needs clearance. It either got hotter than before or contaminated with metal.
 

Traskel

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I don't know if you guys have seen this video. Burt explains the incredible BD-5 story from the inside. Very similar to Raptor. The BD-5 performance was assumed to be laminar with incredible speed. The engine and driveline was unworkable. The deposits were refundable... but convertible to non-refundable. And more.
Not saying Raptor copied the business plan because I don't see how anyone beside Burt would know what happened with the BD-5 deposit scheme but eerily similar.
...And doesn't the BD-5 hold the record for # of crashes/total # of flying airframes?.. I don't recall the actual stats but I remember being horribly surprised.
 

Traskel

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Billski, nobody was name calling. The subthread was about that giant plastic spool piece that was proposed to be installed to segregate oil from inside to out. The way it is used in the design, my understanding, I could be wrong, is that it is trapped end to end and there is oil pressure inside and outside. Someone suggested that making it out of Teflon might help. I just suggested that using Teflon for that would cold flow or creep. I have lots of experience with teflon lip seals, glass loaded or not, and don't disagree at all that they can be used as lip seals where the lip and housing pressures are designed to keep them in place and help them seal and with the slipperiness of Fluoropolymers it works great. But Teflon as a large structural lump. Not a chance. You load it and it moves. You load it more and it moves more, you load it more and it keeps moving. Used to represent a Plastics company that made Teflon seals and all kinds of other fluoropolymer seal bits and pieces for all kinds of applications. Teflon is a tricky material to those with no experience using it. I've used it a lot.

The Delrin (I think was said) is another story but loaded axially in hot motor oil and on a critical system where failure and catastrophic leaks create all kinds of danger is just irresponsible regardless of what project it's on.
Thank you for providing the materials info. It's always surprising to me how few people know of Teflon's infinite creep characteristic. Even plumbers think that "Teflon tape" is for sealing pipe threads - it cannot seal anything at the remarkable pressures developed between tapered threads, It's an assembly lubricant so that greater torque can be applied to attain the thread deformations need to seal..
 

Traskel

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Using skins for cooling has been done in the past. The Crosby CR-4 comes to mind, but there have probably been others. Since it has been tried, and no one continued to use it, my bet is that it was no improvement over a conventional heat exchanger/radiator.
On the LE cooling tangent of this thread - Significant structural improvements have been made to graphite foams which exhibit remarkable heat transfer, (e.g. POCO HTC). Additionally, much research has demonstrated the efficacy of active circulation control on wings and ducts from the venting of compressed air for drag reduction and/or increased operational AOA regimes on airfoils. Might it be possible to integrate porting a heated airstream from the engine, (from HX's, Turbos, exhaust, etc.), for the active circulation control and when needed send the air first through an augmented graphite foam in direct contact with a carbon fiber leading edge? Not to go all Sci-Fi but various emerging technologies are reaching late-stage development and may be artfully combined for such things without the overt disadvantages of prior attempts at LE cooling. Thoughts?
 

BJC

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Might it be possible to integrate porting a heated airstream from the engine, (from HX's, Turbos, exhaust, etc.), for the active circulation control and when needed send the air first through an augmented graphite foam in direct contact with a carbon fiber leading edge? Not to go all Sci-Fi but various emerging technologies are reaching late-stage development and may be artfully combined for such things without the overt disadvantages of prior attempts at LE cooling. Thoughts?
For a project that, to date, with significant time and money invested, has not demonstrated competence with basic design features that have been successfully implemented on other kitplanes for five decades, any thoughts of developing a new, complex, system is pure folly.


BJC
 

Voidhawk9

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For a project that, to date, with significant time and money invested, has not demonstrated competence with basic design features that have been successfully implemented on other kitplanes for five decades, any thoughts of developing a new, complex, system is pure folly.
So do you think he'll install it before or after flying to California?
 

edwisch

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...And doesn't the BD-5 hold the record for # of crashes/total # of flying airframes?.. I don't recall the actual stats but I remember being horribly surprised.
The quote I've heard is that everybody who survived their first flight in the BD-5 loved the handling... As for "mortality rate," I've heard from fairly reliable sources that the VariViggen may be in that group. Reason being very high induced drag if you got slow and not enough power to get out of it without lowering the nose. Apparently the same is true of the T-38...
 

rv6ejguy

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On the LE cooling tangent of this thread - Significant structural improvements have been made to graphite foams which exhibit remarkable heat transfer, (e.g. POCO HTC). Additionally, much research has demonstrated the efficacy of active circulation control on wings and ducts from the venting of compressed air for drag reduction and/or increased operational AOA regimes on airfoils. Might it be possible to integrate porting a heated airstream from the engine, (from HX's, Turbos, exhaust, etc.), for the active circulation control and when needed send the air first through an augmented graphite foam in direct contact with a carbon fiber leading edge? Not to go all Sci-Fi but various emerging technologies are reaching late-stage development and may be artfully combined for such things without the overt disadvantages of prior attempts at LE cooling. Thoughts?
Ducting exhaust, compressor bleed air or coolant in sufficient quantities for useful gain would be hard to do, heavy and dangerous with the wet wing, not to mention requiring new wings to be built. Never going to happen, Raptor needs to first get the fundamentals right- light weight, reliable systems, cooling and engine/ PSRU, stability etc. before it's even suitable to be flown by the masses. It's nowhere close to any of those goals right now. The last thing it needs is more weight and complexity.
 

Bill-Higdon

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Thank you for providing the materials info. It's always surprising to me how few people know of Teflon's infinite creep characteristic. Even plumbers think that "Teflon tape" is for sealing pipe threads - it cannot seal anything at the remarkable pressures developed between tapered threads, It's an assembly lubricant so that greater torque can be applied to attain the thread deformations need to seal..
Having worked with Teflon wire in multiple occasions and had deal with insulation creep & ensuing shorts which start as intermittents you hope to be able find them before they cause major damage
 

BBerson

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...And doesn't the BD-5 hold the record for # of crashes/total # of flying airframes?.. I don't recall the actual stats but I remember being horribly surprised.
BD-5 probably. The BD-5b somewhat better. Burt was director of development.
 

Wanttaja

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BD-5 probably. The BD-5b somewhat better. Burt was director of development.
I've heard the short-winged BD-5 had a high fatality rate, but, like Bill says, the long-winged variant was much better. Keep in mind the size and design of the aircraft; not much protecting the pilot. If you had $100 in your wallet, you had a better chance to survive if it was 20 $5 bills rather than one $100 bill....

I've met two people with lots of BD-5 experience. Both were complimentary of the aircraft. Les Bervin was the Bede test pilot; he came and talked to our EAA chapter about the BD-5. Dave "Hammer" Harris was a chapter member, flying airshows in a BD-5J and had a VW-powered version as well. Loved both of his planes, used to bring the VW-powered version to chapter fly-outs.

Ron Wanttaja
 

BBerson

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Seth Anderson did a BD-5 article later for Sport Aviation that was complimentary. But he was a professional at NASA. The BD-5 didn't come with a proven engine. So the garage guy experimental engine ones that did fly often failed on takeoff and pitched up and stalled because of the high thrust line.
 

malte

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...And doesn't the BD-5 hold the record for # of crashes/total # of flying airframes?.. I don't recall the actual stats but I remember being horribly surprised.
Well, if Peter flies with that engine and delrin collar, he might get an emergency rate of 2 per airframe faster than he'll like.
 

Dantilla

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...And doesn't the BD-5 hold the record for # of crashes/total # of flying airframes?.. I don't recall the actual stats but I remember being horribly surprised.
The original batch of customer-built BD-5s had a horrid record of first flight crashes.
It was quickly learned that the BD-5 MUST be built in a jig. The plans call for several measurements to be taken from the edges of skin panels, but the subcontractor that supplied the formed parts did not cut the parts to the exact dimensions required.
They assumed the builder would trim to final size.
Yet nowhere in the plans is this mentioned, or even exact dimensions given for the builder to verify.

Build a BD-5 according to the plans, and it will be crooked.
Build a BD-5 in a proper jig, and it has wonderful flying characteristics.

So unfortunate the early accident record is why the BD-5 still has that reputation.
 

Traskel

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I've heard the short-winged BD-5 had a high fatality rate, but, like Bill says, the long-winged variant was much better. Keep in mind the size and design of the aircraft; not much protecting the pilot. If you had $100 in your wallet, you had a better chance to survive if it was 20 $5 bills rather than one $100 bill....

I've met two people with lots of BD-5 experience. Both were complimentary of the aircraft. Les Bervin was the Bede test pilot; he came and talked to our EAA chapter about the BD-5. Dave "Hammer" Harris was a chapter member, flying airshows in a BD-5J and had a VW-powered version as well. Loved both of his planes, used to bring the VW-powered version to chapter fly-outs.

Ron Wanttaja
They must be a blast to fly once one allocates to it and I know the original engines caused much grief. Like most everyone on this forum I wanted one from the start..
For a project that, to date, with significant time and money invested, has not demonstrated competence with basic design features that have been successfully implemented on other kitplanes for five decades, any thoughts of developing a new, complex, system is pure folly.


BJC
I in no way meant to imply that PM should try to use such tech. The thread had departed into a more general discussion of LE cooling challenges and I wanted to offer some emerging prospects for future applications, e.g. Carbon foam formed in direct contact with a carbon fiber LE. Composite design need not stop at structural applications...
 
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