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Boomstick

Retiring the Flying Brick

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So I got the Flying Brick up to 62.3mph but crashed it and worse, I didn't even get it on video. The "great crash" as I call it, broke the bumper in half, the bumper mount in half, cracked the chassis, broke one of the battery retainer pieces, broke the rear body mount brace, bent two of the aluminum rims, tore a hole in one of the tires and ripped the swingarm cups out of the chassis. Also the speed control and battery both went flying. I think one of the front wheel bearings seized up which caused it to hook a left into the curb right in front of me at 60+...

It was a violent crash to say the least.

So, I totally rebuilt it and replaced every broken part and even replaced a couple with aluminum parts.

Then I decided I wanted to run it 60+ without crashing it so I lowered the front of the body by modifying some Traxxas body mounts hoping the lower front stance would make it less likely to flip backwards at 55ish...

It didn't help at all...

 

This is my first three attempts after the rebuild and I crashed it on the third. That crash broke the chassis again, broke the front bumper and brace again, ripped one of the wires out of the plug for the steering servo and sent the speedometer flying into the grass. I also bent both of the aluminum swingarm retainers and bent the frog skid plate...

So, I just finished replacing the chassis for the second time and I've decided that I'm done with speed runs for this old girl. She's been through a lot and deserves a break for a while (no pun intended). The Blackfoot wasn't designed to go highway speeds...

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Yellow road paint imbedded between the tire and beadlock ring... Wow... Just wow.... 

How much force does it take to do that???

 

 

IMG_20210324_012619.jpg

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That's impressive, the speed runs and the damage done to the chassis and other components.

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Welcome to the club.

I got my FF03 to 103km/H and on the second try another day I tried to use Foam touring tires instead the rubber ones to stop ballooning of tires.

Imon the first straight I went full throttle just to find out the stopping distance on foam tires is much greater then on rubber. The car ended up in a wall under a 90 degree angel with at least 80kmH with little or no braking as the foams just didnt grip.

the rear lower arms popped out and the front turnbuckles popped out. The rest was Ok. Just assembled it all back and goog to go.

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1 hour ago, Boomstick said:

The Blackfoot wasn't designed to go highway speeds...

Thanks for sharing! I'm sure it was definitely fun to try making a speedrun Blackfoot, and you are clearly aware of the humor in the name "flying brick" since bricks don't fly, so arguably you just proved a point that didn't need proving :D

So what's next? Why don't you build a scale pirate ship and see if it can take off? You can call it the "Flying Dutchman" :lol::lol:

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This is what's next...

"Bugsy"

That king cab next to Bugsy comes after...

Bugsy will tell me if the wheelie problem with the Flying Brick is a torque or aerodynamics problem...

IMG_20210321_125850.jpg

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18 minutes ago, Boomstick said:

Bugsy will tell me if the wheelie problem with the Flying Brick is a torque or aerodynamics problem...

Allow me to save Bugsy from total destruction:lol::

It's an aerodynamics problem. If you want Bugsy to go fast without flying, you need to reduce the amount of air going under it and use the air that's going over it to push it down. The video you shared clearly shows that the flying brick has an approximate 'lift-off velocity' when it's going a certain speed, so I put my money on aero.

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40 minutes ago, DeadMeat666 said:

Allow me to save Bugsy from total destruction:lol::

It's an aerodynamics problem. If you want Bugsy to go fast without flying, you need to reduce the amount of air going under it and use the air that's going over it to push it down. The video you shared clearly shows that the flying brick has an approximate 'lift-off velocity' when it's going a certain speed, so I put my money on aero.

agreed.

stick a touring car wing on the hood 

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What about a Big Oly roof spoiler and some sort of front splitter?

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8 hours ago, DeadMeat666 said:

Thanks for sharing! I'm sure it was definitely fun to try making a speedrun Blackfoot, and you are clearly aware of the humor in the name "flying brick" since bricks don't fly, so arguably you just proved a point that didn't need proving :D

So what's next? Why don't you build a scale pirate ship and see if it can take off? You can call it the "Flying Dutchman" :lol::lol:

Bricks do fly, just ask the wet bandits from Home Alone LOL.

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I think you'll find aerodynamics are a problem, but not the problem. The ORV chassis is sloppy by nature; even new built, they have a degree or two of play in the front wheels in both toe and camber. Combine that with monster-sized tires that squirm around, and a very short wheelbase, and you'll be lucky to keep it in a straight line for very long at that speed.

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@Boomstick ahahah, amazing! Congrats, pal. I always loved the concept of pursuing high speed with unsuitable vehicles, started long ago with mopeds modifying them as a teenager. You are achieving great results and thumbs up for the perseverance as well.

Good luck for your future speed runs

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I'm thinking on giving it one more go at 70mph which has always been my goal. In reality, it's $15 for a new chassis, $5 for the bumper and $10 for the brace parts tree... The 5 star wheels I'm running now are much stronger than the saw blade style I bent. In this last crash (seen on the video) I managed to imbed yellow road paint in between the beadlock ring and tire without bending the wheel. If that doesn't bend a wheel, I don't know what will. 

So I'm thinking of running a couple layers of duct tape reinforced with lexan from under the truck, around the the bumper and up to the hood turning the front into a wedge of sorts.

I didn't really want to go that route, I wanted to break 70mph with it looking pretty stock without lowering it, putting car tires on or doing any extreme body mods (spoilers, diffusers, etc) but if I really want a Blackfoot that will do 70, I might just have to build a wedge...

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Do you want to do 70, or do you specifically want a Blackfoot to do 70?

Because if you want to go fast for cheap, you want something like this:

https://www.rjspeed.com/kits/drag/2003.html

618-rjs2003.JPG

Drop your electronics from the Blackfoot straight into that and you'll be breaking the speed limit in no time.

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1 hour ago, markbt73 said:

Do you want to do 70, or do you specifically want a Blackfoot to do 70?

Because if you want to go fast for cheap, you want something like this:

https://www.rjspeed.com/kits/drag/2003.html

618-rjs2003.JPG

Drop your electronics from the Blackfoot straight into that and you'll be breaking the speed limit in no time.

I want the Blackfoot to go 70... 

Where is the fun in buying an r/c that is already made to go that fast???

Seriously, this all started when I saw AndyRT200 video going 49.1 with his Blackfoot. When we were kids we followed mine down rt100 in maryland at 45mph and I thought "you know with brushless motors and 3s batteries, I can beat that" and I have, 54.3 to be exact. In fact I'm sure I could get 70mph or more if I can get these wheelies under control. One of my runs went 62.3 but I didn't get it in video and I crashed it.

 

I still haven't been able to go full throttle without wheelying which is why I'm still not sure if it's torque or aerodynamics or a combination of the two causing this...

 

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27 minutes ago, Boomstick said:

I want the Blackfoot to go 70... 

Where is the fun in buying an r/c that is already made to go that fast???

Seriously, this all started when I saw AndyRT200 video going 49.1 with his Blackfoot. When we were kids we followed mine down rt100 in maryland at 45mph and I thought "you know with brushless motors and 3s batteries, I can beat that" and I have, 54.3 to be exact. In fact I'm sure I could get 70mph or more if I can get these wheelies under control. One of my runs went 62.3 but I didn't get it in video and I crashed it.

 

I still haven't been able to go full throttle without wheelying which is why I'm still not sure if it's torque or aerodynamics or a combination of the two causing this...

 

Hmm the wheelie problem is probably too much torque from the motor. It seems like you need more runway to be able to ease into it. Are you at the limits of your radio range?

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I'm wondering actually if adding a bit of weight might help. Some wheel weights to keep them planted might be worth a try and then maybe a bit of extra weight over the front axle to stop it trying to lift.

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How about a front spoiler/diffuser shaped a little like a snow plow? That way it'll retain a MT look, whilst also providing downforce at the front and stopping air flow getting under it the car. It'll also add some front weight, which will also help. A snowplow could also reduce drag, which becomes the predominate factor as speed increases.

A rear spoiler will push the back wheels down, which will help acceleration, but also provide a turning force lifting the front up. You're also putting more weight behind the back wheel, which will tip the car further into wheelie mode. 

I could imagine the car is acting like a wing, the airflow over the top of the car has a longer journey to travel compared to he bottom so it flows faster. The difference in speed of the air flow creates pressure imbalance or lift. This means the torque forces from the motor lifting up the front are exaggerated.

Of course the second the front lifts up the airflow hitting the front at and angle provides more lift too.

I could imagine something like the below, but shaped to look more like a snowplow.

ten time winner paul dallenbach at pikes peak


 

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@Boomstick do you have a thread somewhere of the mods you've done so far to get to this point? I'm assuming with the speed and progress you've achieved, things like stiffer rear springs/damper oil and nose weights have already been done? 

Aero will certainly make a significant difference, taping the shell to the tub to minimise the parachute affect of the shell will not only help avoid wheelies, but increase your top speed too. 

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11 hours ago, B.RAD said:

@Boomstick do you have a thread somewhere of the mods you've done so far to get to this point? I'm assuming with the speed and progress you've achieved, things like stiffer rear springs/damper oil and nose weights have already been done? 

Aero will certainly make a significant difference, taping the shell to the tub to minimise the parachute affect of the shell will not only help avoid wheelies, but increase your top speed too. 

Other than replacement parts made of aluminum, it's pretty stock. I want to keep it as stock as possible as part of the "experiment". I did replace the molded body with lexan which I cut the back window out of to reduce the parachute effect (which didn't help) and lowered the front of the body to try to create more down force but that also had no effect. I have stick on wheel weights I'm going to try next before I go all gung-ho with duct tape spoilers...

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Ha ha! Ok cool, great experiment! Stiff rear springs might help by reducing some of the rearward weight transfer in acceleration, possibly small gains but gains nonetheless! Hard foams in rear tyres will also help (just thinking that reducing some of the rear mechanical grip might offer some marginal gains too). You probably don't want to go too extreme though or you sacrifice handling and at those speeds, the last thing you want is your car bouncing over everything rather than absorbing the bumps! 

Glad you're not giving up, I'm excited to see where you can get to 😊

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Thanks for this. I hope your not offended but this put a big midweek smile on my face. I just love the ambition and wow that bricks got some moves  :-)

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