I'm going to put a jet engine on a bicycle.

[Sad, little man]

Two and a half years ago I built this bike. And ever since, people will not stop asking me if it's electric, or telling me that I should make it electric. So now just to get everyone to shut up about making it electric, I'm going to put this jet engine on it. It has 36lbs of thrust. The internet will not give me a straight answer as to how much horsepower this equates to, but hopefully it's enough.

http://gtxforums.net/attachment.php?attachmentid=3846&d=1638420734

http://gtxforums.net/attachment.php?attachmentid=3848&d=1638421325

3846

3848

[Random]

:up::up:

[Dicknose]

Jets + rockets are measured in thrust. They are generally constant force engines. You get the same acceleration at all speeds!!! 0-100, 100-200, 200-300 all the same. Ok the aero drag increases to offset this.
The power then depends on the speed, the faster you go the more powerful.

Internal combustion is best modelled as constant power (assume the average power thru the rev range that the gears allow).
But this means that acceleration drops as speed increases.

[Dicknose]

ps good luck, get someone else to video and then post it up

[Yw-slayer]

This thread is full of WIN

[Crazed_Insanity]

Assuming you and your bike weighs about 200lbs and ignore aero drag as you speed up, you might achieve 0-60 in like 16s?

Good luck!

So I guess you finished your van?

[Rare White Ape]

Is it an electric jet engine?

[Sad, little man]

Is it an electric jet engine?

No sir, at maximum thrust it consumes 0.6L/min of either Jet A, kerosene, or diesel.

I looked into the electric jets (ducted fans) but it seems like they would consume way too much electricity to be feasible.

[Sad, little man]

Yeah the van is basically finished at this point.

Here's another photo of the engine.

http://gtxforums.net/attachment.php?attachmentid=3849&d=1638456214

3849

[Crazed_Insanity]

Dude, why are you SLM? You are too awesome... after this bike experiment, you should try to build a jet pack or something.

Transform yourself into an Iron Little Man! :p

[Dicknose]

Would need a few of those for liftoff!!

Anyone for cold thrusters on their non-Tesla car??

[samoht]

Jets + rockets are measured in thrust. They are generally constant force engines. You get the same acceleration at all speeds!!! 0-100, 100-200, 200-300 all the same. Ok the aero drag increases to offset this.
The power then depends on the speed, the faster you go the more powerful.

Internal combustion is best modelled as constant power (assume the average power thru the rev range that the gears allow).
But this means that acceleration drops as speed increases.

:up:

love the way we can count on GTXF to have a good concise explanation of things that would be a ten-page argument on lesser forums.

I did a quick calc, I think 36lbs is 16kg which is approx 160N of thrust.
If I'm right, it appears that you'll have about 1hp at 10mph, increasing proportionally with speed so 2hp at 20mph, up to 10hp at 100mph if you went that fast.

Top speed will be whatever speed you have 160N of drag force at.

[Sad, little man]

:up:

love the way we can count on GTXF to have a good concise explanation of things that would be a ten-page argument on lesser forums.

I did a quick calc, I think 36lbs is 16kg which is approx 160N of thrust.
If I'm right, it appears that you'll have about 1hp at 10mph, increasing proportionally with speed so 2hp at 20mph, up to 10hp at 100mph if you went that fast.

Top speed will be whatever speed you have 160N of drag force at.
Yeah it is 160Nm of thrust, hence why the engine is called the Cheetah 160. How much force is 160Nm of drag? :? This is all so puzzling.

[samoht]

Yeah it is 160Nm of thrust, hence why the engine is called the Cheetah 160. How much force is 160Nm of drag? :? This is all so puzzling.

https://www.exploratorium.edu/cycling/aerodynamics1.html

Putting in 78mph and zeros for the velocity and zeros for the other inputs, that outputs a drag of 159.9N.

That's probably a lower-drag bicycle than yours, and doesn't account for rolling resistance. At a total guess, I'd say you should be able to get over 50mph, based on this. Probably worth pedalling it up to 20mph to get it going, then see what the jet can do.
Suggest wearing motorbiking protective clothing if you're getting towards those sort of speeds.

[Rikadyn]

You should do two of them for balance...

[Kchrpm]

Suggest wearing motorbiking protective clothing if you're getting towards those sort of speeds.

Definitely agree with this.

[Sad, little man]

Yeah I will definitely wear more protective gear whenever I really wind it out. Only challenge is what do I do with it all when I want to go back to riding it as a bike, because no way am I going to pedal a bike in hot stuffy motorcycle gear.

[Sad, little man]

You should do two of them for balance...
My bank account says no.

[Dicknose]

Drag numbers are hard to do without some experimentation.
As long as you have an approx number, test it and get terminal speed and work backwards.

[Dicknose]

Yeah it is 160Nm of thrust, hence why the engine is called the Cheetah 160. How much force is 160Nm of drag? :? This is all so puzzling.

Being pedantic - in case you are doing calc or posting elsewhere...

Thrust (force) should be in Newtons (N).
Nm is a torque. Thats a force at a distance. Rotating stuff (like car engine) have torque. As do levers. When its applied via wheels it ends up back as a force.

And just to be even more confusing, that dimensionally torque and energy are the same - Force * distance. But you should never use Joules as the unit!
Force and distance are both vectors (have a direction). Energy is when the force and distance are in the same direction (or opposite direction).
Torque is when the distance is at right angles to the force.

[samoht]

Drag numbers are hard to do without some experimentation.
As long as you have an approx number, test it and get terminal speed and work backwards.

Yeah. Best experiment I could think of would be a coast-down test, pedal it up to a certain speed, stop pedalling and see what the speed each second thereafter. A phone app w/ GPS might possibly be accurate enough to do this and log it. Do it in both directions and you could potentially account for gradient and wind, assuming the latter remains fairly constant. A phone app connected to a sensor counting a magnet on the wheel would be more accurate tho.

(Since the jet is yet to be attached).

But yeah, super-hard to work out a theoretical calc for the pictured bicycle with you on it. I guess that racing bicycles are relatively well-modelled and thus reasonably representative figures are known, but this thing is a lot different from one of those :)

[samoht]

And just to be even more confusing, that dimensionally torque and energy are the same - Force * distance. But you should never use Joules as the unit!
Force and distance are both vectors (have a direction). Energy is when the force and distance are in the same direction (or opposite direction).
Torque is when the distance is at right angles to the force.

You know, that had never occurred to me. I'm totally doing my wheelnuts up to 50 kJ now!

[Crazed_Insanity]

:lol:

[Sad, little man]

Just a little update. I was having trouble getting the little telemetry box to connect to the jet engine. The company sent me some replacement parts, and it turns out the fuel pump/electronics module was bad. So now I have the engine electronically up and running. I have not actually plumbed all the fuel lines into it and fired it up, but that will be next.

The biggest technical hurdle in all of this was how I was going to control the throttle on the engine. Since it's designed for a radio controlled airplane, the fuel pump module is looking for a throttle signal from a radio control receiver. It's the same signal that an RC car uses for the throttle and steering servos if anyone is familiar with those. But luckily, there is a library for the Arduino that is specifically made to control servos. So I was able to use that to send the proper throttle signals to the electronics on the jet.

I also managed to connect an e-bike throttle to the Arduino as an input. So ultimately, I'm going to have a standard twist grip throttle on my handlebars to control the jet engine, which I think is pretty cool. I have seen other people put jet engines on bikes before on YouTube, but they are all really hacked together installs with weird little knobs (servo testers) to control the jet. I didn't think it seemed very practical or safe to be fiddling around with a little knob while you're riding a jet bike. So I'm looking forward to having a nice clean install, and a twist grip throttle.

[Cam]

You're going to be famous/infamous.

[Crazed_Insanity]

Yes, we are witnessing the birth of Iron Little Man.

[Sad, little man]

I spent a lot of the winter traveling, so I haven't had a ton of time to work on the jet engine. I did get it running on a little test stand I made for it, but shockingly it had some kind of problem, and seized up. :eek: I talked to the company and they were really good about it, despite both of us having no idea what happened, and they hooked me up with a new engine, so that's amazing.

Ran the new engine on a test stand with no issues. While I was in Arizona over the winter a friend let me strap it onto the back of his late '70s Yamaha that had a blown engine. I pulled out the motorcycle engine and trans to lose some weight, and put the jet onto the luggage rack on the back. The weight of the motorcycle, even without the engine and trans, was a pretty formidable match for the little jet. However it did still move. The jet had a few fuel errors and kept shutting itself down, so I never really got to let it rip for a prolonged run on the motorcycle. I'm back home now and over the next few weeks I'm going to work towards putting it on my bike and hopefully figuring out the fuel issues. It uses a lot of fuel, so I think the problems may have been related to some restrictions in fuel flow somewhere.

[Cam]

I look forward to further updates. :cool:

[Crazed_Insanity]

Assuming more than expected fuel consumption means its burning too fuel rich, then maybe air not flow properly is the problem?

Anyway, hope you can get it working because I'm sure we're all dying to see... :p

[Sad, little man]

Jet engines control the throttle by just adding or removing fuel. I thought a lot about whether or not a jet engine can actually run "rich" or "lean" because effectively if you add fuel you are also adding air, because more combustion will make the turbine wheel spin faster, which is on the same shaft as the compressor that pulls air in, thereby adding more air. This was kind of a mind bender and it just made my head hurt. But now I think the potential for a jet to run rich or lean probably comes more from the overall design of the engine rather than how much fuel you're delivering. If it's designed right, I would think the compressor would be sized right and spin the right speed based on however much fuel is being burned.

Anyway, here is the one video I took of the jet when I had it strapped onto an engine-less Yamaha in Arizona. I was really hoping for more speed since I really wanted to blast across the desert on a jet engine. I think I could have gotten some decent speed going if I could have kept it running longer. On this run, the ECU threw an error that it wasn't able to reach the desired RPM properly. You can hear I let off the throttle a few seconds before it died. I think I accelerated back up to full thrust too fast and it didn't like that. It's kinda weird to me how this thing is made to go in R/C planes and it seems like the default for any issue that it senses is to just totally shut down the engine. But, oh well. :?

Also I was tucking my head down because I was watching the little telemetry screen that I stuck onto the fuel tank. ;)

You can also get a sense of how godawful loud this thing is. It really is shocking how much noise comes out of something this small.

https://youtu.be/fhCEMEM__mo

[Crazed_Insanity]

Yeah, not really a jet engine scientist... never played around with RC jets as well... so can't really help you there.

Anyway, that engine sure sounds cool! I was expecting to see a fight jet zoom pass, but then the video and audio mismatch kinda made my head hurt. :p

[Sad, little man]

Yeah, not really a jet engine scientist... never played around with RC jets as well... so can't really help you there.

Anyway, that engine sure sounds cool! I was expecting to see a fight jet zoom pass, but then the video and audio mismatch kinda made my head hurt. :p
Yeah, sadly the jet was a little outmatched trying to move a whole motorcycle, even without the engine. But my bike is probably only about 30% the weight of that motorcycle.

Yes it's kind of hilarious though. It's pretty rare to see an underpowered jet propelled vehicle. :lol:

[Dicknose]

Probably more useful to boost a vehicle that's already at speed, thrust/weight is not great!

[Sad, little man]

Probably more useful to boost a vehicle that's already at speed, thrust/weight is not great!
I'm still struggling to understand the physical difference in how power is delivered by an engine vs a jet, why a jet's "power" technically increases with vehicle speed, and why a jet would be more useful to boost a vehicle already at speed.

[Kchrpm]

As a non-expert: more speed = more air/air pressure = more power.

My presumption is that jet engines are low torque but high rpm to make their power, so a jet engine of the same peak horsepower as an engine with a much lower redline will have tons more torque.

Also, since your jet engine is just providing thrust and not being transmitted to a wheel, there's no torque multiplication.

[Crazed_Insanity]

Since jet engines are not mechanically connected to a wheel nor propeller, torque is no longer relevant. All it does is produce thrust force pushing on his bike or a plane. I suppose we don't care about torque on rocket engines as well because these engines simply produce forces that push on whatever vehicle they're on. Newton's Force=Mass*Acceleration means that assuming the same jet force, if SLM could increase overall acceleration by reduce his bike mass or lose some weight himself! :p Or if he has the budget, he could just add more forces(Jet engines)!

I guess jet engines are more like turbos..., it has compressor blades that suck and compress air to mix with fuel and creating the thrust. In a way you are correct that faster means more air and more speed. Ramjet/Scramjet engines no longer requires compressor blades to suck in and compress the air because as you fly in super or hypersonic speeds... you are already ramming in lots of air... and the shock waves will further pressurize the air. I think SR-71 has both kinds of engines. Regular jet engines to get it up to supersonic speeds... and then ramjet kicks in. Those ramjets literally gets more powerful the faster you go. But of course SR-71 is still speed limited by the melting point of its titanium airframe.

Anyway, surely SLM will figure out ways to make this sad little bike go faster! :D

Regardless of speed, it sounds really awesome. Maybe SLM could just install one on his car. Whenever at a red light, just start blasting Top Gun theme music and then turn the engine on! :D

[Random]

I'm still struggling to understand the physical difference in how power is delivered by an engine vs a jet, why a jet's "power" technically increases with vehicle speed, and why a jet would be more useful to boost a vehicle already at speed.

Remind me to see if I saved my gas turbine design notes from school. It's a mass flow thing, but I don't recall the exact details.

[Dicknose]

Jet/rockets work by "throwing" stuff out the back at high speed. Rocket has exhaust, jet also has air from intake. Some others like electric thrusters have a propellant.
These have the property of fairly constant thrust (esp if the vehicle speed is much less than the propellant speed) - hence "thrust engines"
https://en.wikipedia.org/wiki/Thrust

This is fundamentally different to internal combustion propulsive engines (propulsive as in pushing)
Firstly the source of power is expansion of hot gas pushing on a piston (which ends up pushing the wheels). A rocket is expansion of gas to create high speed exhaust.
Compare sitting on a wheeled cart and pushing off against the ground, instead of throwing bricks backwards to move you forwards!!

So why do we have jets and rockets? Mostly because they are in the air or space and you dont have anything solid to push against. They also work well at high speeds and dont require gearing. Rockets also work in air and space (actually better in space!)
But they are very inefficient. Weirdly they get more powerful (and more efficient) as speed increases. Most of the energy ends up wasted as excess propellant momentum.
Or if you want to think of propulsive engines as pushing using the Earth - nearly all the energy goes into the vehicle, almost none into moving the Earth. Side effect of conservation of momentum when one object is much heavier than the other - the lighter object gets most of the change in velocity (car v earth - its virtually all velocity to the car). Kinetic energy depending on v^2, this then means most of the energy goes to the lighter object. Hence pushing on Earth is way more efficient than throwing stuff that weighs much less than your vehicle.

Hence why no one uses jet cars - except for the land speed record!

TL;DR - its a push vs throw

[Rare White Ape]

So................................................ .....

























What would happen if you rode that bike on a conveyor belt?

[Godson]

Jfc. That shit again? 😂

[Dicknose]

What would happen if you rode that bike on a conveyor belt?

Actually that's the point! In one annoying question.

[Rikadyn]

Hence why no one uses jet cars - except for the land speed record!

TL;DR - its a push vs throw

https://www.ronpatrickstuff.com/

[Sad, little man]

But they are very inefficient. Weirdly they get more powerful (and more efficient) as speed increases. Most of the energy ends up wasted as excess propellant momentum.
Is the efficiency of a jet directly proportional to the speed it's moving, or is it not a direct correlation?

I guess my real question is, the speed that I'll be moving on any vehicle I put this on seems pretty insignificant in comparison to the speed the exhaust is moving out the back. So is the power of the jet in motion just the speed of the exhaust coming out of the back plus the speed the jet is moving through the air? Or does the increase in power compound or rise exponentially as the jet begins to move faster through the air?

[Rare White Ape]

I think the simple fact is that the bike and rider is too heavy for the capacity of the jet you have. Unless I'm mistaken it looks like a turbine for a model airplane, and they're designed to propel a 20 kg aerodynamic vehicle at speeds over 200 km/h in the air. I'd say that you could grab onto a model airplane with it running at full throttle and hang onto it quite comfortably without it slipping from your grip... assuming it doesn't burn your face off.

Compare that to holding onto a 100 mm diameter fire hose pumping 2000 L of water per minute, where the velocity of the water at the nozzle is about 20 km/h. It's easily enough force to give your whole body a workout just standing there.

So think back to what we all know about power and torque: to move the bicycle and rider you need to shift a larger volume of air to overcome the mass and the rolling resistance. With a jet engine you'd soon run into the law of diminishing returns because a single engine with that amount of volume is moving into helicopter engine territory and would weigh over 200 kg, plus it would spin fast enough to shoot you up a drag strip in 5 seconds. By that time you're strapping a bike to a jet engine!

There is a reason why paramotors use a big fan:

https://img.aeroexpo.online/images_ar/photo-mg/182195-14523717.jpg

The vehicle + rider mass is in the ballpark of a standard bicycle configuration and they can apparently reach speeds of around 70 km/h. These motors are designed to meet the requirements for shifting that much mass at a specific speed, where a small jet engine is not. The secret is in the combination of RPM, propeller design and diameter. The same things that dictate why wind power turbines only use three really thin blades: it's the most efficient way to achieve that specific task.

But notice up above how I said a 'single' engine? This might be the clue to the jet engine problem. Time to Kerbal it up and add more thrusters.

[Sad, little man]

Ok lemme just be clear here, everyone realizes that putting the jet on the motorcycle in the video I posted was just to try it out, and the actual bicycle it's ultimately going on weighs at least 2/3rds less than the motorcycle in the video, right?

[Crazed_Insanity]

Is the efficiency of a jet directly proportional to the speed it's moving, or is it not a direct correlation?

I guess my real question is, the speed that I'll be moving on any vehicle I put this on seems pretty insignificant in comparison to the speed the exhaust is moving out the back. So is the power of the jet in motion just the speed of the exhaust coming out of the back plus the speed the jet is moving through the air? Or does the increase in power compound or rise exponentially as the jet begins to move faster through the air?

Inlet air speed will definitely effect efficiency. That’s why jetliners cruise within certain speeds/altitude ranges to achieve best mpg #s. Flying too fast or too slow will cause airlines to waste more fuel!

However, mass of your bikes probably won’t make much difference on the efficiency front. You’ll just accelerate faster by going lighter! ;)

[Dicknose]

Is the efficiency of a jet directly proportional to the speed it's moving, or is it not a direct correlation?

I guess my real question is, the speed that I'll be moving on any vehicle I put this on seems pretty insignificant in comparison to the speed the exhaust is moving out the back. So is the power of the jet in motion just the speed of the exhaust coming out of the back plus the speed the jet is moving through the air? Or does the increase in power compound or rise exponentially as the jet begins to move faster through the air?
The power (and efficiency) are proportional to vehicle speed!
So yeah at the sort of speeds you will be doing, the power will be low and efficiency terrible.
See how much fuel it uses and you will get the idea!
Sure there is a small improvement as incoming air has some extra pressure, but that's tiny compared to overall poor efficiency. Not much you can do - that's just a fact of life with thrust engines.

Nerdy physics...
work = force * distance
power = work/time = force * distance/time = force * velocity
You are producing a reasonable amount of force (and it will remain roughly constant across a wide range of speeds), but the "fixed force" nature means power is low at low speed. The engine is producing full power (and fuel consumption tells you that!), just that its mostly going into the exhaust, not moving you forward!

The reverse works against internal combustion, as they are approximately "fixed power", they lose force as speeds increases, hence their acceleration gets smaller as speeds go up.

And as an even nerdier side note... deep space craft do "slingshots" on planets where they pickup speed. They effective fall under gravity and pick up speed, then lose some as they pass and go back "up" again. Just that they gain more on the way down than they lose on the way up. Thats the slingshot, come out faster than you went in/ But it also means that they are going their fastest as they are closest to the planet, much faster than their final exit speed. So they also do engine fires when they do these slingshots because its more efficient to use the engines at higher speeds. And when you have limited fuel (or propellant for electric powered that dont use fuel) you want to maximise your efficiency.

[Dicknose]

btw I do find it ironic that I use "post quick reply" and then add a new chapter to my physics posts.

[Dicknose]

Ok lemme just be clear here, everyone realizes that putting the jet on the motorcycle in the video I posted was just to try it out, and the actual bicycle it's ultimately going on weighs at least 2/3rds less than the motorcycle in the video, right?

That will reduce mass, increase acceleration and improve power efficiency. But that improvement is constant for all speeds. If you 1/3 weight then you get 3 times the improvement. (and how heavy was that motorcycle? Was it heavier than you?)

The nature of "power increases with speed" wont change. Still worth you pedalling to help it get up to speed.

Have you watched any "car v jet" videos. They show the effect of low speed acceleration.
https://www.dailymotion.com/video/x6qpc
https://www.youtube.com/watch?v=Y9YsxO30PXI - this ones shows bike has best low speed acceleration, the car is next best, the jet is last. But the jet just keeps accelerating and as speeds increase it easily catches them. The car catches the bike because clearly the bike throttled off as jet went past!

And while these are quick car and bike, that's also a damn serious jet. Put a commercial aircraft and it would take much longer to catch the car + bike.

[Sad, little man]

Thanks for all the insight DN.

Anyway, as life often does, lots of things have pulled me away from putting in work on the jet, but today I'm making good progress. I was continually vexed by how on earth I could simultaneously hold the jet precisely where I wanted it in relation to the bike so it was perfectly aligned with the direction of travel of the wheels, and weld in supports to actually affix the jet to the bike at the same time.

Finally I settled on welding the jet to the bike with thin flexible metal rods, and then just muscling the jet into place exactly where I wanted it, and then while the thin metal rods were keeping it in place, I tacked more permanent supports in place.

I think that was the hardest part of this whole thing, so hopefully it won't be too long until I have this functional.

[Sad, little man]

(and how heavy was that motorcycle? Was it heavier than you?)

Yeah even without the engine and trans the motorcycle was probably over 300lbs, maybe 400. The bike weighs about 100, let's say 110 with the jet, fuel tank, and fuel on it.

[Dicknose]

Looking forward to how it goes!

Good luck, stay safe and have fun

[Sad, little man]

Ok, so, first thing is first, it's pretty much done. Secondly, visually this came together amazingly and I think I may have created one of the absolute most badass bicycles in existence. It occupies an alternate reality where the modes of transport in the Jetsons came true.

But lastly, I genuinely don't know what I'm going to do with this. This is not the Jetsons, and society just wasn't structured around people blasting around on jet engines. It's antisocial, it's menacing, it will damage the hearing of anyone who comes near it that isn't wearing earplugs. Not to mention it's just terrifying to be around when it's running. It idles at 34,000RPM. I really think I may have gone too far here. Maybe I should just shelve this and settle for a nice ebike conversion. :|

Thus far I have not actually ripped around on it under jet power, but I did take it to the most remote local park I could find just so I could start it. It seems to be getting air bubbles in the fuel lines somehow, not sure what that's about.

http://gtxforums.net/attachment.php?attachmentid=3922&d=1656547780

http://gtxforums.net/attachment.php?attachmentid=3923&d=1656547796

3922

3923

[Kchrpm]

Fucking wild.

[Crazed_Insanity]

Not gonna fuck it, but it looks wild! :p

[Rare White Ape]

It DOES look visually stunning!

However there is an imbalance in that the headlight and engine are a similar size. Maybe you could source a smaller headlight...

...or a bigger jet engine :assclown:

[Sad, little man]

It DOES look visually stunning!

However there is an imbalance in that the headlight and engine are a similar size. Maybe you could source a smaller headlight...

...or a bigger jet engine :assclown:

If you look back at the photo on page 1, you'll see I swapped out the headlight. That IS the smaller headlight. The old one just made the whole thing look way too frumpy and front heavy. I like this one. Any smaller and I wouldn't be seen well at night. I also like the comet shape of this one as it lends itself to the long design of the bike.

Anyway, I took the jet out to a local park for another test run yesterday. There was a kids baseball game going on on the other side of the park. They would have definitely heard it, but I stayed pretty much out of view, so they probably just thought it was a plane.

Luckily there was much less air coming through the lines this time. I almost reached full thrust and didn't see much air. I thought maybe I had a restriction somewhere in the fuel system that was causing cavitation of the fuel. (Essentially too much suction in the fuel lines causing the fuel to vaporize from the vacuum force.) Since the engine uses half a liter of fuel per minute at full thrust, it's very possible to have too much of a restriction in the lines. But the main line from the tank to the fuel filter device that runs most of the length of the bike is 3/8", so I should be ok. I also modified the cap on the fuel tank to be able to vent more than it did originally.

When I got close to full thrust I could feel it trying to push the bike away from a standstill, so that was pretty cool. I think the only place I can really let this rip without bothering anyone will be on some roads on the outskirts of the Detroit airport, so after the holiday weekend I might ride it out there and actually ride it a little.

[Crazed_Insanity]

So awesome man!

You know, I’m beginning to think you might need to install a head or back rest or something?

You know, just in case the jet engine breaks off at full throttle… it won’t impact you directly?

Kinda wish you installed 2 engines on the sides of the rear wheel. You could disguise them as bike exhausts! Harley Davidsons will sound like kiddie bikes compare to yours! :lol: