The "Double Whammy" Dragbike Build

#1
The Double Whammy was built in two weeks to inspire another fellow OldMiniBikes Member to get his Twinibike done for the Billetproof Drags.
Got a great deal on a Doodlebug and a couple HF engines from Square Chopper here on the board, and thats what started the project rollin'!

Nice clean Doodlebug to cut up!



oh boy, new stuff!!


First step was to take all the garbage off the engines and paint the blue BLACK!


Attack of the Clones


Then get rid of all the excess brackets, and cut her in half!


NO TURNING BACK NOW!!!


Cut the bars down, I'll bend them down later for a better angle.


14 inch stretch.


Looks really Nerdy here, but I wanted to make sure the engines were going to clear everything.


Got the bars bent and primed, couple a holes too. Seatpan idea started too.


Getting closer to looking like a dragbike.


Checking tank clearance, yes its a fire extinguisher, soon to be tank.


Testing went great, time for paint.


Trimmed down the seatpan and filled it full of holes.


The Double Whammy! Done and raceable in two weeks time.










Some of the neat things about the bike... I don't know about top end, but the torque is through the roof! The exhaust was made from bicycle handlebar tubing, the cable stop is from an electrical block, the skateboard looking seatpan was bent in a drainage grate, chaingaurd is a steel shelf bracket, gas tank was a fire extinguisher, Ruddy Red Primer and Industrial Gray spray bomb paint, homeade spring chain tensioners, the back clutch is a two spocket to make the whole project work, and work it does, it is a blast to ride. We'll see next month what it does in the 1/8th...stay tuned.
 
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#3
12 on the clutches, I had a 54 on the back and it would smoke the tire, so I just put a 44 tooth on yesterday, should give more top end. :thumbsup:
I couldn't find any sprockets smaller than 54 to fit the Doodlebug wheel, so I ordered a 44 tooth snowmobile clutch and drilled it out to fit. That's what I did on my Bottle Rocket bike too.
 
#4
OK cool. I have a 17t clutch and 54t rear with a 12" tall tire, which is pretty close to your new setup. I have to run a jackshaft though and I'm going to get gears pretty close to each other so I can flip them around to tweak gearing a bit there.
 
#6
Thanks Hellaslow.
Hot Rodders used Model T's back in the day because they were plentiful, cheap and easy to modify to go fast.
I think the Doodlebug's are the "Model T's" of the minibike world. :thumbsup:
 
#7
VIDEOS! i think you deserve dragbike build of the year. for that being done in 2 WEEKS is just awesome. anyways. i love this bike, think i might copy you.. :thumbsup:
great job,

motormind
 
#8
are the front and rear tire the same size? also what size? are you running a tube?

i know i know... one last Q...
do you have build pics of the gas tank?
 
#9
Thanks!
No pics of the tank, forgot to do that :doah:
I cut the top flange off, moved it to the side (which is now the top) and then plugged and welded in the front. I'll post a close up when I get a chance. Tubless tires, same size. 13 x 5.0 x 6
Hopefully a video tomorrow, rainy all day today.
 
#12
Between raindrops I had my 8 year take a couple quick videos.
They are short, but you get the idea....
Click on the pic to play.

Start up


Take off.


Flyby
 
#16
Dave, the gearing seems good.
Still takes off pretty hard, I haven't gone full throttle yet, I wanna let the engines break in a little more before I run wide open.
Even if top speed aint that high, the way it pulls now is good enough for me, you can try it out at the Track next month. :wink:

Duppy-Yeah I converted the extinguisher, it was a steel one so I could weld on it. I cut the flared top off (where the handle was), drilled a same size hole in the side and welded it in over that, The cap is a garden hose cap. Then I filled in the now open top hole with a plug (second pic). Welded two large bolts on top for mounting, and then drilled and tapped two holes in the bottom for gas line.
To smooth around the cap, instead of body filler, I used Quick Steel to make it look smoother, harder to sand but in the long run should look better longer.



This was the top of the extinguisher.
 
#18
I guess so, in the front I just found a plug that fit and used a little JB Weld on the threads to make sure it sealed really well, so far so good.
The top I used some threaded tubing half way in, left enough out for the hose cap, which I drilled a hole to vent and put a round piece of neoprene under the rubber washer to seal it.
 
#19
I can say from personal experience that it is literally impossible to ride this bike without a HUGE grin on your face! My boy done GOOD on this one!
:thumbsup::thumbsup::thumbsup:
 
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