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Tandem trike questions


Gary Boyco
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I have been researching for a DIY paramotor trike build powered by my Kawasaki 440a with a Magnum redrive and 70" Prop. Naturally with that big of an engine and prop the trike will be wheel launch only. I have learned a lot about hang points, torque compensation, A-assists, etc. Footflyer.com is a great way to learn the dynamics of PPG flight and there is a series of videos on youtube by Scout Paramotors that teaches a class on good paramotor design but I have not found a good description of some of the things I am seeing in videos of some bigger tandem trikes. 

My first question is about these levers on the top tubes. What are these? I assume they are for activating speedbar without a bar? I had this very idea before seeing it realized here. Seems like the best way to add speedbar to a trike. Am I right? This is speedbar?

This incredible hang system seems overly complex and heavy unless it serves some very useful purpose that I have not been able to figure out. What do you call this item and does anybody know where to find a good description of it's purpose and use/design?

I am not making a tandem trike I am making a heavy hauler cross-country trike. I will want and need speedbar and a relatively high wing loading for speed and wing stability and quick re-inflation.59e80d3593a3a_Tandemtrikequestions.jpg.763e9a832b7904954139672cbb9a79c3.jpg

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So when you say you trying to assemble a 'heavy hauler' what do you have in mind? Is it heavy to be strong or heavy with a large fuel capacity for longer flight time?

I have a heavy trike with Rotax 503 but my wing connection looks nothing like the one above.

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I've had a quick look at the Fresh Breeze web site http://www.fresh-breeze.de/en/home.html which I think that photograph comes from.

My guess is the levers are some sort of trimmer adjustment?

The hang system bracket appears to have a spreader bar at the front, probably to assist easy inflation or ensure correct shaping of the canopy.

The only other sort of canopy I have seen with an elaborate hang system is a powered parachute type, more of the traditional ram-air design than typical PPG canopy.

Maybe contact Fresh Breeze with a couple of queries?

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12 hours ago, Guy said:

So when you say you trying to assemble a 'heavy hauler' what do you have in mind? Is it heavy to be strong or heavy with a large fuel capacity for longer flight time?

I have a heavy trike with Rotax 503 but my wing connection looks nothing like the one above.

I am designing a "heavy hauler"....It can haul heavy loads. Fuel, camping gear etc. So basically a tandem with a storage area rather than a second seat. I want to make it short like a solo trike with the storage under my butt as far back as possible to keep the CG from moving around too much under differing loads.  I doubt I would use the hang method shown in the picture but I would like to understand it as I have seen this on several heavier trikes so there has to be some advantage to this configuration with bigger machines.

Edited by Gary Boyco
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11 hours ago, alan_k said:

I've had a quick look at the Fresh Breeze web site http://www.fresh-breeze.de/en/home.html which I think that photograph comes from.

My guess is the levers are some sort of trimmer adjustment?

The hang system bracket appears to have a spreader bar at the front, probably to assist easy inflation or ensure correct shaping of the canopy.

The only other sort of canopy I have seen with an elaborate hang system is a powered parachute type, more of the traditional ram-air design than typical PPG canopy.

Maybe contact Fresh Breeze with a couple of queries?

The pic comes from a random Youtube video but yes this appears to be a Fresh Breeze XCitor. Many others have these same features though. The levers are either trim, speedbar or a combination of both. Yes it does look a lot like hang systems as used in PPC. This is why I am thinking there may be a good reason to do it this way with heavier machines. Maybe I should be looking at PPC design considerations rather than those specifically for PPG. 

Although Fresh Breeze will probably be happy to answer basic questions about their hang system and trimmers I was hoping for a good technical description of how that hang system works. (and what needs to be changed for different weights, CG's etc.) Much like the page on footflyer that explains hang points or torque compensation. I doubt they are going to want to describe their system well enough to allow me to design my own. Actually maybe they will...Scout paramotors has a dynamics class on Youtube that gives you enough information to reverse engineer a Scout with it's unique active torque compensation, so maybe....I guess as long as they don't think I am trying to go into competition with them? If I explain what I am building they may be ok sharing a little knowledge.

I'd rather just find an explanation somewhere or get a good basic description  of what we are looking at here from someone who knows for certain what the design considerations where in the development of these two systems. I am happy to experiment (safely) but I do need to have a good grasp of the how and why of it or it would be very unsafe to experiment. I have enough knowledge now to build a safe normal trike but what I am aiming at is just slightly OUT of the ordinary so I have to make sure I am safe through understanding. Besides I would like to benefit from whatever advantage this hang system offers IF I should decide it is worth doing after I completely understand it.

I could hook up levers to trim or speedbar or a mixture of both but as I am NOT a professional designer that would be very unsafe unless I am doing something the same way it has been done before and for which I have gained an understanding. I generally only feel safe in aviation when I am doing something that has been done before and that has been completely explained to me. I will design and modify but only with the required knowledge. 

Edited by Gary Boyco
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The first thing I have confirmed is that they refer to the lever mechanism as the "trim lever" and state that it "Works like the brake line: In order to fly faster pull both levers aft, for curve flying push inner lever fore"

"Even during climb you may trim the XCitor to a straight flight with the trim levers. Just push the lever on the side you want to move to slightly forward. Remember, the brake levers act like a brake line – pushing them forward makes the XCitor move into that direction. Vice versa the other lever may be pulled back."

I think the lever travel is too short for it to be pulling speedbar but it is far from clear that is what we normally think of as "trim". Perhaps it is more like a brake offset. Either way I believe I have gotten enough information about it to know that they only have this trimmer system because their hang system has to deal with massive CG shifts and control line offsets that they don't have and can't use normal trimmers.

I am leaning toward a system similar to the Trike Buggy Bullet where the actual clip in point is very low at the hips providing weight shift and strong feedback in roll but has line keepers on the top tubes that gives it high hang point stability in the pitch axis as this seems like the best compromise to me. 

This analysis has just made me realise that I have never seen a trike with speedbar aside from that weird one that has the front wheel that hinges DOWN so it hangs below you allowing the use of speedbar and even emergency foot landings in rough terrain. 

Is there a way to use speedbar when triking? If not can anybody think of a reason to not carefully experiment with ways to pull on the speedbar lines via a lever or pedal? I know that the main consideration would be to make sure you can release as quickly as you normally can when using conventional speedbar. A pair of pedals on the frame should be able to pull and release just like a speedbar. If the lines were attached right at the top of the pedal then the travel and required force would feel exactly like normal speedbar without the stowing/unstowing issues. Just pull your feet off of the steering pegs and push on the pedals. I would love to be able to lock them in whatever position I wanted (like a pedal type parking brake) but that would be dangerous unless I could reliably and quickly release it just as fast as releasing speedbar. Of course I would be careful to follow the wing manufacturers directions regarding use of speedbar and trims together.

Dunno, this all just occurred to me because of thinking that the XCitors levers might be speedbar rather than trim. I clearly have more to think about now.

Does ANY trike have speedbar?

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Aaaaand after a day of searching the terms "paramotor trike speedbar" in various combinations I finally find this video showing a gentleman using speedbar in a completely conventional manner on a small but full frame trike. The frame just does not get in the way of his using speedbar. My design certainly will as it has something of a "floor" so if I want to use speedbar (and I do) I will have to use pedals.  

 

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If you look at the levers you can see a cord runs from each through pulleys to the rear of the square wing attachment device. Pulling the rear of the device down pulls the trailing edge down and slows the wing. Moving one lever more than the other tilts the wing diagonally and hence trims it to maintain a straight flight.

So this is just like speedbar and normal trimmers in that you can trim each side independently. 

There also appears to be a red strap either side which looks like it is a safety back-up in case the trim cords fail. Looks like the strap limits how far the square frame can tip if the cords fail.

Quite a clever mechanism!

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14 hours ago, AndyB said:

If you look at the levers you can see a cord runs from each through pulleys to the rear of the square wing attachment device. Pulling the rear of the device down pulls the trailing edge down and slows the wing. Moving one lever more than the other tilts the wing diagonally and hence trims it to maintain a straight flight.

So this is just like speedbar and normal trimmers in that you can trim each side independently. 

Which RESEMBLES trim and speedbar but  works in a completely different way. I would need to know a LOT more about the geometry than that. 

There also appears to be a red strap either side which looks like it is a safety back-up in case the trim cords fail. Looks like the strap limits how far the square frame can tip if the cords fail.

No that is the reserve 'chute attachment. 

 

14 hours ago, AndyB said:

Quite a clever mechanism!

 

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