Top Fuel Dragster Conversion

[rckcrwlr]

OK guys...need your opinions...

I can get my hands on two Megatech Dark Thunder Nitro Dragsters.

A buddy has access to a warehouse that we can set up a strip.

Now my question, do you think it would be worth converting it to brushless? Has anyone done it before?

It has a two speed tranny that goes into a rear straight axle. The only relief for the drivetrain is the Clutch bell.

I will need to use the mech brake unless I can rig something in the, so called tranny. (Haven't looked at it close yet)

What do ya think???

[Semi Pro]

looks like a great conversion, the easy route would be to convert it to straight axel but keeping the belt drive and two speed shouldnt be that hard

[What's_nitro?]

I'd get rid of the 2-speed and the clutch since BL has plenty of torque. Use the motor brakes to save weight. I would run 6s on a MMM and use the punch control setting to avoid tire spin. From what I've seen those dragsters do, a setup that gives you a 60-70mph top speed would be fine.

[rckcrwlr]

Originally Posted by What's_nitro?

I'd get rid of the 2-speed and the clutch since BL has plenty of torque. Use the motor brakes to save weight. I would run 6s on a MMM and use the punch control setting to avoid tire spin. From what I've seen those dragsters do, a setup that gives you a 60-70mph top speed would be fine.

6S?

I was thinking a little less...that would be a huge brick...I could possibly do 3-2S along the chassis.

I was thinking 4S low Mah...being that it is a dragster.

I was actually thinking of using a combo of both brakes to control a stop...

[What's_nitro?]

Originally Posted by rckcrwlr

6S?

I was thinking a little less...that would be a huge brick...I could possibly do 3-2S along the chassis.

I was thinking 4S low Mah...being that it is a dragster.

I was actually thinking of using a combo of both brakes to control a stop...

6s 5000 would be a brick. I know- I have one! 6s 3700 would be sufficient. Look at it this way, the car is gonna have sooo much more torque than the stock nitro motor. With torque taken care of; weight = traction. Putting a brick in it might not be a bad thing!

Low-capacity cells are OK, as long as they can supply enough burst current not to hold you back at the starting line! Adding a few extra capacitors on the main ESC leads would be a good idea, too.

[TexasSP]

There is a drag racing league here in Houston that has top fuelers and funny cars. I would PM SunnyHouTX for some info and he can shoot you in the right direction.

[SunnyHouTX]

rckcrwlr: YGPM.

In other words, I did a similar project with Megatech Afterburner parts

[SunnyHouTX]

BTW, for the way the rear end is set up, I'd recommend a direct drive system which is very easy and cheap to do. You don't need any more than 3S to get a very quick dragster. With a motor of around 4000kV, and a 3S lipo around 2000mAH, you will get in the 1.7sec ET range around 65 - 70 mph in the alotted 132ft. You will only have to play with tire diameter to go faster.

[rckcrwlr]

Originally Posted by SunnyHouTX

BTW, for the way the rear end is set up, I'd recommend a direct drive system which is very easy and cheap to do. You don't need any more than 3S to get a very quick dragster. With a motor of around 4000kV, and a 3S lipo around 2000mAH, you will get in the 1.7sec ET range around 65 - 70 mph in the alotted 132ft. You will only have to play with tire diameter to go faster.

I like the way you are talking...

[mohanjude]

I did a conversion by adding the rear end of a traxxas rustler - runs really well on a brushless motor - if you are interested I will get some pictures. It really is a blast to drive

Mohan

[rckcrwlr]

Originally Posted by mohanjude

I did a conversion by adding the rear end of a traxxas rustler - runs really well on a brushless motor - if you are interested I will get some pictures. It really is a blast to drive

Mohan

Interesting...I have a VXL Pede tranny sitting in my box of "stuff"... Let me see whacha got...

[SunnyHouTX]

If you go with a standard spur/pinion set up, be prepared for stripped spur gears. The direct drive set up eliminates that, and you will only have to change tire diameter and motor Kv. Motor Kv only if nothing else makes the car go faster.

[What's_nitro?]

Originally Posted by SunnyHouTX

BTW, for the way the rear end is set up, I'd recommend a direct drive system which is very easy and cheap to do. You don't need any more than 3S to get a very quick dragster. With a motor of around 4000kV, and a 3S lipo around 2000mAH, you will get in the 1.7sec ET range around 65 - 70 mph in the alotted 132ft. You will only have to play with tire diameter to go faster.

Wow really? 3s 2000mAH? That's only like 600W burst power on a 25C lipo... It doesn't seem like enough.

[SunnyHouTX]

What you have calculated is continuous power. The set up I mentioned will peak at about 1100W due to voltage draw down as well as the shear amount of current it will pull on initial start up. Drag racing puts conventional thought out the door. And you don't really want "all the power you can get", mostly because the limiting factor is almost always the available traction. Traction is pretty hard to control with a low Kv, high voltage system as the torque is too much to control.

Just to illustrate, here is a look at the draw down of a 3S Thunder Power 3300mAH 25C/50C pack within one pass I made:



We run with LVC turned off so as not to mess with the flow of current, if any body is wondering how the pack went below 6V. It only recovered to about 9V at the immediate end of the race but, normalized around the 12V mark afterward. This is why it's very important to use high C rated packs, so that the recovery phase is quicker and the end voltage is as high as possible for top end RPMs.

I have no idea what the real power output of my dragster is since there is no way to measure the current demand in it. I estimate it to be in the 200A range, so a good estimate will be around 1800W or higher. My Litespeed dragster does the 132ft at a best ET of 1.45s @ 88mph+, just to give an idea of what's going on.

A shameless plug here, but check out my website in my signature to see my race cars and such.

[What's_nitro?]

Originally Posted by SunnyHouTX

What you have calculated is continuous power.

Oops.... So drawing the cells down that far for such a short period wont hurt them? Have you tried adding more caps to the system?