22TDI Engine Placement Questions

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jchovernut
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Re: 22TDI Engine Placement Questions

Post by jchovernut » May 12th, 2012, 9:25 pm

Here's a few frame grabs from the DVD "Welcome to the World of Surface Skimming," one of Barry's earlier videos that shows quite a bit of early SEVTEC development, including his early foray into hang gliding. The pics show a couple Model-A's and a Model-B. The A had one horizontal lift fan, and the B was the immediate predecessor to the Explorer with the twin vertical fans. Reviewing these, it looks like they're all twin 2-blades, but I vaguely remember the original Explorer plans showing the 3-blade Ivo for the twins. This shows the folding guard concept to get the hardware to trailering width.

This video is a great look back at SEVTEC history and shows Barry and his craft through the years of refining his designs into the latest Vanguard derivatives. It's well worth having around for historical footage and the wide range of hovercraft filmed. The snippet of Barry flying the "Yellow Machine" to the Canadian Coast Guard base in suit and tie is well worth the admission alone ;)
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Wolf's Model-A
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Model-B
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Model-A Folding Guard
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Model-A Unfolding Guard
Screen shot 2012-05-13 at 12.24.27 AM.jpg (82.27 KiB) Viewed 2311 times
John Carter
John Carter
SEVs: Vanguard, FanTastic, Prospector, Explorer
Others: StarCruiser, UH-18P, RX2000
http://www.hovernut.com

bandit1538
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Joined: February 15th, 2012, 9:52 pm
Location: Skamokawa Wa.

Re: 22TDI Engine Placement Questions

Post by bandit1538 » May 13th, 2012, 12:11 am

jchovernut wrote:I believe the 'classic' Explorer plans, and its predecessors, the 'Model-A,' & 'Model-B' all had twin 72" props. If turned to the right angle, they'd be inside trailering width, and the design incorporated folding outboard prop guards for trailering as well. I always thought the twin prop look and sound was rather cool. But after the Alaska trip and operating with Bryan around the Puget Sound, the single 84" sure seems a lot safer and more manageable. But...if you need the clearance, Clarance, twins might do the trick.

Pat, how do you plan on getting the props to counter-rotate? Do you plan on 'figure-8'ing' the drive belt on one side? I've never seen such a thing on a hover. The Piper Seminole twin-engine airplane I got my multi-rating in had counter-rotating props, but the bass-ackwards engine was actually designed to run that way. Most twins run in the same direction.

Guy, I can attest the bilge pump is a PITA to get to ;) Other than going to the twin props to lower overall height, you could always 'kneel' under the bridges by dumping lift and 'airboating' under the bridges. Or possibly even carry a small trolling motor to hang over the side or bow to thrust the hover under the obstruction while in 'displacement mode.'

Cheers,
John Carter
I did think about figure 8ing a belt but also thought of having an aluminum gear box with a second output shaft with two matching gears inside to do the trick.
Pat
If it aint broke, don't fix it.

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jchovernut
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Re: 22TDI Engine Placement Questions

Post by jchovernut » May 13th, 2012, 5:51 pm

Pat, I just don't think the efforts are worth it at all to counter-rotate the props! It's quite beneficial on an airplane because of several factors: couter-torque, slipstream induced lift, P-factor, and yawing tendencies...none of which affect hovercraft, but all of which could lead to the operating engine taking the pilot to the scene of the crash if not managed properly. You have only one prime mover turning both props, a failure of which would kill all of your propulsion, not just one side. Even so, two same-turning props should produce the same thrust with respect to RPM even if individually driven, with no undue adverse effects upon one's failure other than yawing that would occur with only one offset prop operating...countered by opposite rudder.

The drive engineering and longevity/reliability would certainly be interesting to see, if you continue down the counter-rotating road. A straight-cut set of gears would certainly be noisy...might look for helical engagement if possible. Funny how a carnival ride drive comes to mind where a couple tires engage each other in friction to reverse rotation ;)

John Carter
John Carter
SEVs: Vanguard, FanTastic, Prospector, Explorer
Others: StarCruiser, UH-18P, RX2000
http://www.hovernut.com

bandit1538
Posts: 162
Joined: February 15th, 2012, 9:52 pm
Location: Skamokawa Wa.

Re: 22TDI Engine Placement Questions

Post by bandit1538 » May 13th, 2012, 6:58 pm

jchovernut wrote:Pat, I just don't think the efforts are worth it at all to counter-rotate the props! It's quite beneficial on an airplane because of several factors: couter-torque, slipstream induced lift, P-factor, and yawing tendencies...none of which affect hovercraft, but all of which could lead to the operating engine taking the pilot to the scene of the crash if not managed properly. You have only one prime mover turning both props, a failure of which would kill all of your propulsion, not just one side. Even so, two same-turning props should produce the same thrust with respect to RPM even if individually driven, with no undue adverse effects upon one's failure other than yawing that would occur with only one offset prop operating...countered by opposite rudder.

The drive engineering and longevity/reliability would certainly be interesting to see, if you continue down the counter-rotating road. A straight-cut set of gears would certainly be noisy...might look for helical engagement if possible. Funny how a carnival ride drive comes to mind where a couple tires engage each other in friction to reverse rotation ;)

John Carter
Hay, there we go, I'll use two tractor tires so the "V" lugs will match so they don't slip to reverse one side........ :lol:
Thanks for the info John.
Pat
If it aint broke, don't fix it.

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