Pros and Cons of the Thumper

The Rocky Mountain Thumper
is a very different kind of Paramotor
Two months ago I traded in the beloved Simonini and became the proud owner of a Briggs and Stratton Trike buggy. The 4 stroke power plant was designed and built by Terry Lutke and the Flexfoil Trike was developed for PPG by Chad Bastion.

The biggest downside to going 4 stroke is the lack of fun things to do while not flying. Having spent the last 4 years immersed in this sport, I was comfortable with all the the wonderful little things that are a normal part of a PPG pilots life. The nights spent in the garage replacing compression springs or driving to the airport after dinner to pick up AV Gas. If I wasn’t searching the Internet for the best buy on Castrol TTS, I was waiting for the UPS man to deliver a 160 dollar starter sprocket. It seemed like I was either working on the maching or flying it.
For every minute in the air there was an equal or greater amount of time occupied with the care and feeding of my 2 stroke paramotor. If it was blowing…no problem, I have a pull starter to rebuild.


These days… things are different, because the heart of the “Thumper” is a Briggs & Stratton, twin V, 4 stroke motor. Thousands of these motors are built every year and the economy of scale makes it possible to produce a very affordable motor with excellent manufacturing tolerances and a beautiful fit and finish. They are designed to run 10,000 hours at peak horsepower, so it’s not unreasonable to expect to fly hundreds of hours with nothing more than an annual check-up and oil change. When necessary, parts and expert service are readily available at the local lawnmower repair. Gone are countless hours tinkering with the machine. No mixing fuel, exotic tools or translating owners manuals. Now ,when it’s too windy to fly, the best I can do is wish for better air. You still have to be ready for a “motor out” and have an emergency landing site within the glide slope but the reliability of this motor instills a confidence that allows for flights that would not have attempted before.

But…. When it is flyable, the thumper is always ready to go and the first thing you notice is the happy rumble of the Briggs & Stratton. On my first flight it was so quiet that I completely forgot the step where I put in the ear plugs and put on the helmet. I realized my mistake just as I was taking off and few seconds later so did everyone at the Salton Sea when my ball cap went through the prop. …..WAAK….ear protection is still necessary but with a four stroke power plant, noise is reduced by thirty percent or more. At cruise with the RPM’s reduced it would not be impossible to use a cell phone.
The next thing you notice is that the thumper doesn’t suffer from the constant vibration that plagues two stroke motors. Its eerie, when the prop is in balance and the motor is running for level flight, its possible to forget all about the power plant and enjoy the ride. Occasionally you will find a node on the power band that sets up a harmonic vibration, but it’s easy to bump up or down the RPMs to stay in the sweet spot. Flying a two stroke I was often ready to land at 45 minutes or an hour. Without the vibration I’m much more relaxed and feel like I’ll be able to fly as long as the gas and weather will permit. Cross country flights of 100 miles or more are certainly possible.
Not for the con…Only one so far…There isn’t the instant power you get with the Simonini. I won’t be able to fly the contour of the surface like I used to. This year when I fly the dunes it will be from 30 feet above the tops instead of down in between the dunes. Flying the Thumper is going to require anticipating my power needs. It might be better with a different wing and it’s going to be fun to try them out.

Flight 270 Simms

The wind speed chart shows moderately high & gusty winds from the south south east. Sunset was at 7:00pm.

Very short flight. The predicted weather was to be 5 mph from the east but I got 10 to 12 gusting to 15-18 from the south. It came down a bit (see Weather chart) , I launched and did one lap before landing by the truck. There were a few issues.

1. It’s not a tumble weed…it’s tangle weed.

Wind from the south caused me to set up at the North end, by Hampden…It’s 500 yards and and a hassle. You have to push the buggy uphill and across the grain of a dense tangle of dry weeds. They are bone dry and flat to the earth…They are like a bunch of tumble weeds that had been run through the laundry… full dense branches 24 to 36 inches long and waiting to get hooked up in the lines. It reminded me of the first days of learning how to ground handle at Brian Smith’s home field. I tried kiting like I had been over at the truck but it wasn’t much fun. Every inflation the wing picked up a few branches and I spent way too much time “de-weeding the wing” and throwing the debris down wind. I suppose the good thing was that I realized the potential for fouling the wing and searched out the least congested spot to set up for launch.

2.When I powered up the buggy bogged down. It was almost a replay of the last flight of the Simonini. The wing came right up in the prop wash but the trike wasn’t moving…I threw my weight back and forth like a toddler on a play toy …luckily, first time…the buggy broke loose and began to accelerate. While this is happening I was watching the PPS start to fold …and just before gravity took over it miraculously re-inflated. The take off was crisp and the climb was better. Launching into a wind with this machine is kinda nice.

BUT… I could have done without the pucker of
imagining my wing getting sliced and diced by # 60
inch Ivo steak knives.
Once up…The air was mixing and rowdy…I decided to land right away…It might have been allot better 800 or 1000 feet higher… but it didn’t feel good… so I landed. The good news was that I set final approach for the truck and came in beautifully. The bad news was that I didn’t mash the throttle do a touch and go and fly for a couple of more minutes.

While I was packing up, it sure seemed flyable, but those are the breaks the weather was too marginal to hassle with the weeds for the last few minutes of light.

Note to self:

When you are launching on softer soil, push the buggy back and forth over the first few yard of runway to smooth the surface and prevent getting the wheels into a rut during the critical first second of power.

Flight 269 Good Air at last Simms

Good flight….Trimmers-in launch.

55 degrees

Light wind from the NW

High overcast

(no gps track)

I’m getting used to the long take off but I was a little surprised by the way I floated at 10 feet for a while before it finally started to climb. I’ve been letting the buggy build enough speed to take off without brakes but it might be a good idea to ad some brake and see if it improves the climb.

So…I ventured away from the home field and went over to Bear Creek Park for a look see. I should have tested the foot steering but I think I’ll wait until I get some kind of cruise control to free up my hands. Same for the trimmers…next time I get into some decent air the trimmers are going out!

The biggest thing to get used to is the slow run up the power band or maybe it’s just flying with less power. Touch and goes are tricky because you have to be powering up for the climb-out before you touch down. Another thing is I don’t have the power to do any hard banking turns, it might be better with the trimmers out…I’ll have to wait for the next flight.

Next time the wind is coming out of the east I’m going to try the Eden III 28m…if it climbs slow at least I’ll have plenty of room to work with.

267 & 268 Simms

It was a beautiful day

Sunny and warm,

The Dawn was calm with very light winds which built as it got warmer. I was loading the buggy about 3:30pm and noticed gusts from 3 to 15 which came and went very quickly. I was hoping that it would mellow as the sun got lower. Since I was a little early I stopped at S & B “South Side Power” … I ordered high altitude jets for the carb and B.S’d with the staff for a while. They are a good bunch and I think they will be very helpful.

Simms … Two ten minute flights. Equipment was without issue. 65 degrees.
Climb is good but the takeoff was much longer. Reading last weeks log,… I notice all the same things. I’m still tentative on the wing and missing the old throttle.

The first flight, I climbed to 400 feet and landed. The run out was very long with the trimmers out but the wing came up very fast. Very ratty air all the way to the ground. I was more than happy to use the entire runway and make a long straight approach. There were puffs I flew threw that would slow me down and change the glide. Not dangerous but not the best place to be making tight turns either.

By the time I had walked the entire width of the field the wind was starting to mellow. A 15 year old kid was tagging along…nice kid I’ll try to give him a little more attention next time. 🙂

Second flight came 10 minutes after the sun had set behind the foothill. I kept it short and enjoyed a little better air. Trimmers in, wing came up slower, but takeoff was quicker. Climb out was sluggish at first but came up nicely. Landing was perfect …power on dragged the back wheels for a long time before I felt the front wheel touch.

Getting used to the Thumper/Powerplay Sting… It’s bigger, heaver, and slower to react. I miss the Simo’s snap but the trade off’s of the 4 stroke are still worth investigating. The place where it will really shine are long x-country flights. And…I have not had a good opportunity to do that this year. Guess I’ll have to get up early and put on my Michelin Suit to do it right.

Rigging the Reserve Harness

After much fussing and fretting this is the way I have rigged the Reserve Harness

The bridal is on a seperate attachment aft of where the riser’s straps attach to the buggy. They run through the saftey straps below the “hang point loops” and on top and outside of anything that could foul during deployment. I selected the right side because I fly with the throttle in the left hand. It will not help with any torque issues but I don’t think torque is to much of a problem with the thumper 4 stroke.

Kiting the Sting

The winds have been blowing steady for the last two weeks.
Too soon to put the boat in and to windy to fly.
So for the last couple of days I’ve been taking Monte’s wing out for a little high wind kiting. It comes up good but I’m having a hard time finding the right brake input. Either it wants to overfly and tuck or I’m using too much and the trailing edge puckers and the wing falls back. I’m not sure if it was a combination of trim and wind speed or just the nature of the wing. I think the lines are strung different because it’s a tandem wing.

Chad’s High Altitude Test Flight

Way to go Chad
12,000 MSL

While I was getting my ass kicked at Vance Brand Chad was setting a new record for the 4 stroke Trike Buggy

Here is his report…
Re: 12000′ 4stroker climb out
Posted by: “trikebuggydelta”
Mon Mar 2, 2009 10:01 am (PST)
Thumper High Altitude TestsI went out to El Mirage and the Flying “J” Ranch this last weekend tofly the Thumper. I wanted to launch and land the machine, maybe ahundred times, and really get a feel for it. I wanted to do some highaltitude tests, to see how high it would go and what the climb rateswould be at different altitudes. I got there Friday afternoon, and pulled the Thumper out of my shedand gave the key a try. BrBrBRrBrBr, it sounded like a jackhammer as Irealized that I should have removed the positive battery lead before Ileft last time. I pulled my Toyota over near the Thumper and gave herthe breath of life. I let the Thumper run for close to an hour,letting her charge the battery up so I had a bit of reserve. The greatthing about the Briggs & Stratton motor is that this thing just runs!You simply start it, and it just loves to run. I changed the throttlea few times to 2000 and 3000 RPM, and sometimes I would run it rightup to full (at the pitch I had the IvoProp at, it topped out at around3400 RPM – should have been around 3800), then let her rest at around1200 idling. Finally, started setting up for a flight. Wrong! Once I got in theair, I could see why the Quicksilver Ultralight pilot looked so amused- it was punchy! On the ground, it was maybe 0-4 mph, seemingly niceconditions, but once in the air it was a different story. I did a fewgo-arounds and decided that it was a bit much for me and landeduneventfully. I spent the rest of the afternoon installing the FootSteering, a Reserve Parachute, more velcro for the instruments,getting some more gas and generally tightening everything andpreparing for the evening flight. At just before sunset, I launched again, and enjoyed maybe 30 touch &go’s before it got so dark I was squinting to see. I was flying theDudek Synthesis 34 glider, and it worked beautifully with all thatThumper weight (220lbs) dangling from the lines. I trimmed this reflexglider full slow for this flight, and it inflated perfectly everytime(5 inflations) with the A-Assists and was still fast in the air.Looking at the risers, I saw that full slow is actually a bit slowerthan trim speed, so I set the trimmers at 0 (there’s actually numberson the trimmer) to put the glider at true neutral for the morning flight.Jerry Frost and Pierre Beney arrived this evening, and we spent a goodbit of time ‘Hangar Flying’ around the campfire, watching the moon setalong with that planet, really spectacular!The next morning, I warmed the Thumper up for flight. With the twistof the key, she stirred to life and seemed to be content. I let herrun for a good half hour at idle, something I would never do to any ofmy two-strokes (they would coke-up and choke) while I prepared forgoing high. I used a Flytec Vario for climb rate, a Garmin GPSmap 76for better altitude, and my iPhone with the V-Cockpit app running, avery cool airplane instrument application that uses the internal GPSfor navigation. Only problem was the iPhone was so dim that is didn’tcome out in the pictures. You can see one shot of it in the photogallery on the Altitude screen, just one of the many functions thisapp has. Check out the main screen by clicking the small icon here toyour right. It’s a really cool Application, and I had fun playing withit as I flew. There’s even graphs of the entire flight showingaltutude, speed, climb rate, heading, but no way to save them! At about 8:30, I launched from the Flying “J” Ranch at approximately2850 feet and velcro strapped the throttle at full and sat back andrelaxed, took pictures, video, and wrote down info at each 1000 feetof altitude. On this first flight, I did not write the time down, butyou can see the time on the pictures of the GPS, so it tookapproximately one hour to climb to 8000 feet and 1:25 to climb to12,000 feet. I was still climbing at 12000 feet, but very slowly, andI was cold – I didn’t wear enough layers to keep out the chill. Plus,I had not pitched the prop for maximum efficiency, at ground level itwas only 3400, and it got slower as I climbed. The motor ran beautifully the whole time, not even a hiccup. I amamazed by the four-stroker’ s incredible reliability. I could get usedto this! Trouble is, when I fly a two-stroke again, I’ll be wonderingwhen it will happen…. the inevitable motor-out. This motor is madeto run, and run, and RUN! I let it idle for a few minutes after Ireached 12K, then shut it down for the long glide back down. I reallyenjoyed the views from up high, there was snow on the nearby peaksnear San Bernadino, and I could see all the way to Tehachapi to thenorth and into the LA basin through the El Cajon Pass.

265 266 Vance Brand Airport

Biggest gathering of Denver area Pilots in a couple of years.
Paul Meyer Paul Crazy Ivan Marek Dan Robert Kitilla His son Mark Bennet Some spectators and maybe one or two who’s names I cannot recall.
Plus that’s not all…Wait there is MORE. Three flights of Scoop Divers.

I should have expected some weirdness when the temp dropped from 57 in Denver to 45 at Vance Brand. there were light winds from the North at 3:00. The first flight was ok …a little bumpy but ok.

I had to taxi for longer than usual to get off and the climb out seemed slow. First thing I noticed was that the left Brake line was bound in the risers. I was able to free it without problem since

nothing was crossed …just friction locked.

Max climb was 170 ft / min. I noticed that several of the guys were setting down so I did too. The landing was a bit hard. I killed the motor to0 soon or late and swung under the wing. No damage just didn’t look good. If I’m going to come in dead stick I should decide sooner than 10 feet.
Second Flight was a real pucker. After I set-up, the wind shifted. Rather than re-set I waited and launched when the cycle came around to me. The wing came up much better without the “A” Assists. This time I climbed at 180ft/min When I got to 1200 feet it started to get bumpy and I was climbing at 300ft/min! Even at idle I was still climbing over 100ft/min.
What a ride! The wing was alternately surging and falling back and a couple of times I found myself in a hard bank and starting to get weightless. It was one of those times that you can feel the wind shifting by the way it feels on your face. I was no longer flying in a stable mass of air..It was a good thing that I didn’t have the full height of pad behind me because the extra visibility came in handy to be able to watch the wing. There were several forward surges and while I never saw the trailing edge …it was hairy enough. I think that I was perhaps a little timid on the brakes because I couldn’t feel the wing and the forces working on it. I was contemplating Big Ears when I finally started to descend. I think I was in the worst of it for 3 or 4 minutes and I made the mistake of turning back into it again before I figured out that it was the west end of the box that was being pulled into the clouds…..NO FUN!
The good news is that the landing was better, I left the motor running and came in at idle.
I’ve found a better position to hold the throttle but it is still hard get fine control of the RPM’s. I look forward to using an FB throttle again!
The next time I see lenticular clouds I’m going to think twice. The didn’t seem to be moving but were hanging there sucking up the warmth.
Looking at the profile I was just getting into the nasty stuff when I decided to land on the first flight. It’s probably why I took one look at everybody landing and decided to do the same. The guys that stayed below 300 feet had very little turbulence but there were high winds aloft and the clouds were sucking the warm air from below…Big time…Maybe it was a clue when it got warm about 4:20. (from 45 to 50 plus in about 10 minutes. Be Aware when the temp is fluctuating…And watch out when there are lenticular clouds and signs of high winds aloft !
Later on the ground we stood around and it was so obvious to all of us, that it was ugly at altitude.

Today’s lessons…
1. Watch out when the temp is bouncing around especially if there are lenticular clouds.
2. To Hell with A Assists!
3. Ease the throttle cable
4. Don’t kill the motor at low altitude just to have the prop stopped when you land… come in under power and grease it.