Losi xxx mid motor nosedives?

[Ferret]

Today I finally completed my Losi xxx mid motor conversion and took it for testing on the the track.
I was really surprised how well it handled "out of the box" with my guesswork setup.

However, there was a fly in the ointment; it had a strong tendency to nosedive off ramps unless I launched with a lot of throttle, to the extant of actually flipping forward many times.
The car uses an extra gear so that the motor is spinning in the same direction of the tires.

Did anyone else with a conversion experience this?
Any ideas how to resolve it?

Thanks,
Avner.

[Benh]

What's your drag brake settings, or did you not come off the throttle?

[CBRDEAN0]

Try some lead under the lipo - the xxxCR was designed to have a motor out the back and NiMH cells.

And orange springs would seem a bit hard for the rear - I would have gone with a softer setup - perhaps pinks.

The hard rear end will probably be kicking the back up over the jumps

[Ferret]

No drag brake.
It did happen off throttle, but in the same situations my standard xxx-cr would just get a little or no air. It would not nosedive, land on the front bumper ald flip over.

I could drive around it in testing, but I am real apprehensive about racing the car like this, a small mistake and it's a long wait for the turn marshal...

[CBRDEAN0]

you could always look at the Atomic Carbon CR2 thread (mid engine xxxCR ) and try the setups from there.

The CR2 has won a national so they are pretty dialed with the car.

[Ferret]

I am using the innermost lower shock mounting hole so the spring are relatively "soft". I started the day with reds and the car understeered, switching to oranges made the car pretty neutral.

I want to know if this nose dive tendency is common to mid motor conversion, or particular to mine. It feels too severe to be a simple setup problem. I've been racing conventional 2WD buggies for more than 15 years and never had one nosedive like this regardless of the setup.

I feel my conversion also had a tendency to roll over to the side but this was not as severe and felt like it could be impruved with a better setup.

I'm concerned that maybe the center of gravity is too high or the wheelbase is too long.

[CBRDEAN0]

Originally Posted by Ferret

I am using the innermost lower shock mounting hole so the spring are relatively "soft". I started the day with reds and the car understeered, switching to oranges made the car pretty neutral.

I'm concerned that maybe the center of gravity is too high or the wheelbase is too long.

I would have softened the front first. And put some weight further forward.
Then used softer springs on the rear and moved the shock bottoms out.

If you have used the same wishbone mounting block as the std setup - the wheelbase should be the same as the xxxCR.

How could it be longer ? - have you made a custom rear plate or wishbone mounts ?

[lochness42]

My XXX-CR mid conversion didn't have such problem - it was surprisingly stable in air, I just had problems with spinning out of corners. I just have custom made slim alloy heavy chassis.
When I got my X6 and I added weight as it was recommended I had nose diving car as well, I moved part of weight to the rear and is very nice to drive now.

p.s. here is link to my conversion for comparison with yours http://www.oople.com/forums/showthread.php?t=27655