Modern Car - Atomik V2MR

[fredswain]

I'm not surprised that the 22's didn't work in mid motor. That car is horribly designed when it comes to mid motor. The motor and all the weight is just too far forwards. That's fine for carpet or something very high traction but won't work anywhere else. Those cars have about 62% of the weight on the rear wheels in mid vs 68% in rear. The X6 has about 65% so it's better than the 22 in mid configuration. Setup your cars in mid motor and get 67-68% or so weight on the rear wheels and you won't have any problems on any surface and you'll still have a car more forgiving than any rear setup. That's the real secret to mid motor. It's all about rear weight bias and the point of mid motor is not to shift weight on the front wheels but rather get the weight inside the wheelbase. That's it.

[Hcp22]

I'm not surprised that the 22's didn't work in mid motor. That car is horribly designed when it comes to mid motor. The motor and all the weight is just too far forwards. That's fine for carpet or something very high traction but won't work anywhere else. Those cars have about 62% of the weight on the rear wheels in mid vs 68% in rear. The X6 has about 65% so it's better than the 22 in mid configuration. Setup your cars in mid motor and get 67-68% or so weight on the rear wheels and you won't have any problems on any surface and you'll still have a car more forgiving than any rear setup. That's the real secret to mid motor. It's all about rear weight bias and the point of mid motor is not to shift weight on the front wheels but rather get the weight inside the wheelbase. That's it.

Is that assumption based on a fully equipped car?

[fredswain]

Are you referring to the 22 or mid motor in general? The 22 is a terrible mid motor car on anything other than high grip tracks regardless of setup. The Tardis conversion from Atomic Carbon helps things a bit but I still doubt it's good on clay or dirt.

I have 2 mid motor cars. I have an X6 and an Atomic Carbon Cr2 which is a mid motor conversion for the XXX. The Cr2 right off the bat was terrible on dirt and clay. It's weight fully loaded has about 63% on the rear wheels. I initially had the stock 3 gear setup on it with an external idler but changed it to an Gurnell 4 gear setup. The 4 gear as has been the standard in mid applications does fix one problem with mid motor cars on lower grip surfaces. It allows for a huge amount of weight transfer to the rear on acceleration so forward traction is improved. The downside to the 4 gear is that when you get off throttle you also shift weight forwards tremendously as well which unloads the rear wheels. These are the wheels that brake. You diminish the braking power of the car and also decrease rear end traction off power going into a corner which causes it to slide out easier during turn entry. The lack of weight on the rear wheels compared to rear motor only makes this trait even worse. When you get back on power mid corner the extreme weight shift to the back unloads the front wheels which are trying to steer and you understeer. Suddenly your cornering ability is inferior to rear motor everywhere. This is why so many people in the US hate mid motor. They don't understand what is going on. On the 22 adding the rear weight kit helps but their motor is already placed too far forwards which means the battery is too far forwards as well. You have to add a ton of weight just to get good rear grip. That car sucks in mid motor as a result.

One thing I did on my Cr2 was to somewhat copy what the X6 setup was. I made a new chassis which lengthened the wheelbase. That was another problem with the Cr2. It only had a 10-1/2" wheelbase. I lengthened it to 10-3/4" and placed a fully sized lipo cross chassis in front of the motor. My weight balance now had 67% on the rear wheels from the 63% previously and I added no additional weight pieces anywhere. Immediately it was better to drive on dirt and clay. The rear end didn't want to come out in corner entry anymore and it was far more stable. The weight shift from the 4 gear setup still hurt performance though. The other conclusion that I've reached is that with mid motor you want far less front kick. The XXX had 30 degrees and as such so does my Cr2. You don't need it that high. Not even close. At some point I'm going to custom build a setup that uses 10 degrees of front kick like 4wd cars. The greater the kick the more extreme the rear weight transfer during acceleration and forwards weight transfer during braking. These traits also hurt cornering power.

I then built an X6. I had a B4 front end and bought an X6^2 chassis but instead of using the X6^2 rear end and 4 gear setup I used the original X6 rear end and their admittely poorly molded 3 gear setup. The X6 had about 66% rear weight and the B4's 25 degree front kick. Cornering power was much better than the Cr2 on dirt but due to the forwards weight transfer during acceleration from the rotation of the motor getting off the line is more difficult. With 2 different mid motor cars and lots of playing I could now see what was good about each car and what was bad about both. A few trends became obvious and they apply to other mid motor cars too.

I believe that we have already seen the future of the mid motor car with the Team C TM2. It uses a setup with a sideways mounted motor where the rotation of the motor is cancelled out by the rotation of spur gear and driveshaft. The motor sits on the left side and a shorty lipo opposite to it on the right. This layout will only allow a shorty and not a stick or saddle pack so it is currently illegal in ROAR. I'm sure that car still has a bit too little weight on the rear wheels and the front kick is too much but the layout is sound and the motor is no longer a factor in weight shift front to rear which is a good thing.

What I want to build at some point is the same layout using the B44 rear end with a B4 front end orienting the motor the same way. I'd decrease front end kick to 10 degrees or so and would build a fiberglass or composite tub style chassis to keep stiffness high and weight low. Then I'd make sure the rear weight was around 67% or more. I believe this to be the future of 2wd off road. My X6 is currently being parted out and sold but I am keeping the B4 front end. I am also about to sell the Cr2. I've learned what I've wanted to about mid motor and while I'm a fan of mid motor, neither is a car that give me what I want but I guarantee each is superior to the mid 22 since my friend Matt was running his 22 in mid while I was working on my cars. His car sucked and he sold it.

[JK Racing]

I did more testing/tuning with my V2MR (in rear motor) yesterday. Indoor, med-high grip clay track. Had a generic push I needed to correct, got most of it out. Car is easy to drive and once I got used to it (switching between the RC10, a B4 and this car), I was able to turn some good laps.

A bit more front end tuning, and I should be good then to experiment with other options (after I have a good baseline for the car).

Still using all stock parts, springs and everything.

[kaiser]

keep an eye on the cvd pins, they have a flat spot for the grub screw to catch on, problem is it's a week point and it breaks right at the notch.

i was prepping for today's club race when i saw it. i didn't have a spare so i put a mip pin in that is a little too long and too small in diameter, it will work for a while.
turns out i can't race tonight anyway. but keep an eye on that pin. i can't wait for the tamiya cvd's to show up.

[DerbyDan]

Are you referring to the 22 or mid motor in general? The 22 is a terrible mid motor car on anything other than high grip tracks regardless of setup. The Tardis conversion from Atomic Carbon helps things a bit but I still doubt it's good on clay or dirt.

I have 2 mid motor cars. I have an X6 and an Atomic Carbon Cr2 which is a mid motor conversion for the XXX. The Cr2 right off the bat was terrible on dirt and clay. It's weight fully loaded has about 63% on the rear wheels. I initially had the stock 3 gear setup on it with an external idler but changed it to an Gurnell 4 gear setup. The 4 gear as has been the standard in mid applications does fix one problem with mid motor cars on lower grip surfaces. It allows for a huge amount of weight transfer to the rear on acceleration so forward traction is improved. The downside to the 4 gear is that when you get off throttle you also shift weight forwards tremendously as well which unloads the rear wheels. These are the wheels that brake. You diminish the braking power of the car and also decrease rear end traction off power going into a corner which causes it to slide out easier during turn entry. The lack of weight on the rear wheels compared to rear motor only makes this trait even worse. When you get back on power mid corner the extreme weight shift to the back unloads the front wheels which are trying to steer and you understeer. Suddenly your cornering ability is inferior to rear motor everywhere. This is why so many people in the US hate mid motor. They don't understand what is going on. On the 22 adding the rear weight kit helps but their motor is already placed too far forwards which means the battery is too far forwards as well. You have to add a ton of weight just to get good rear grip. That car sucks in mid motor as a result.

................................

Interesting reading fredswain... I must admit that i've never run a mid motor car on such a predominantly 'loose' surface to really appreciate the fine subtleties in Fr/Rr weight balance - most of out tracks are high grip so we are still normally adding weight in the nose to reduce power-on understeer further! If we do have a slippery area on the track its normally not enough to worry about tuning the car for. That said I've seen very few TLR22s go really well.... our Darren Bloomfield being the driver of one of them!!

I too now have a redundant CR2, I was thinking of selling mine, but it seems they have suddenly become worthless here in the UK, & I've got rather attached to it now (it even gave me a 2nd place finish in the A final at my local club the last time a ran it!). Funny that you ended up with the Gurnell gearbox - I had the PSI version, so both items made journeys across the Atlantic but in opposite directions!

I'm really pleased with my TM2 - but i'm unsure how it will fare on a typical U.S track? The car is sold at a high grip specialist car & indeed it really does seem to have an advantage on the indoor Astro Turf track on which I race over other brands of car... the amount of speed you can carry through the corners is amazing, last week I finished 3rd - ahead of two 4wd cars.... one of which was being driven by a the guy who beat me to the win with his TM2 the previous week! I've also raced the car on an outdoor grass track but although I did well I could sense that it wasn't putting the power down aswell as I would have hoped.

Its interesting that you have mentioned the front kick up - have you seen the 4wd XRay XB4? - many Xray drivers are simply removing the front diff/belt & driveshafts & running the car as a 2wd! Of course being primarily a 4wd car it has a little less built in front kick-up - i've not seen one of these running yet but I hear they go quite well!

Back on subject I'd love to hear how one of these Atomic cars goes in mid-motor layout.

[Hcp22]

Are you referring to the 22 or mid motor in general? The 22 is a terrible mid motor car on anything other than high grip tracks regardless of setup. The Tardis conversion from Atomic Carbon helps things a bit but I still doubt it's good on clay or dirt.

...

What weight distribution should you strive towards for a rear end motor setup?

[fredswain]

Rear motor has plenty of weight rearwards and some can even be moved forwards. Weight on the rear wheels matters but the location of the weight plays a large role too. Weight off the back behind the rear axles has more leverage on the suspension and adds traction as a result. The problem is the pendulum effect in corners. It can be helpful to a point but once the rear end starts to slide out it's gone quickly. My general rule is that you only need as much weight on the rear wheels as is neccesary to get traction. If you are on a slippery track then you need more weight on the drive wheels. A high traction track needs less. This is true regardless of where the motor is.

[kaiser]

FYI the tamiya cvd's for the trf201 are a few mm's too short.

[JK Racing]

Ran my 17.5 buggy last night in 2wd Mod qualified 4th overall, behind 3 sponsored drivers, and ahead of a 4th sponsored driver.

Finally gave in and pulled the stock atomik springs off, went to AE black front, white rear 12mm springs & AE cups. Woke the car up, huge. I went from a horrid push (no matter what tuning I did or tire changes), to crazy steering and fantastic rotation.

I will look over the car and post my set up when I get a chance.

[JK Racing]

Sorry for the crappy, crappy cell phone shot, it was past midnight and my eyes couldnt focus either, LOL

[bearrickster]

fredswain, Very intresting read thank you for all of the advice. I have only raced in parking lots and have been trying to move to dirt with very little to show for all of my work. the way you said it made a lot of sence to me and that doesnt happen to often. I am a little thick

[kaiser]

Ran my 17.5 buggy last night in 2wd Mod qualified 4th overall, behind 3 sponsored drivers, and ahead of a 4th sponsored driver.

Finally gave in and pulled the stock atomik springs off, went to AE black front, white rear 12mm springs & AE cups. Woke the car up, huge. I went from a horrid push (no matter what tuning I did or tire changes), to crazy steering and fantastic rotation.

I will look over the car and post my set up when I get a chance.

sounds good. my atomik might take a back seat to my newly refreshed (+8mm big bore) b4. i ran the b4 in mod this weekend and loved it.
if my week night racing is still limited 17.5 i might stay with the atomik in 17.5 and leave the b4 in mod.

a few weeks ago i raced the atomik on a seriously blown out track and it did really well.

[Mad Racer]

I'm very tempted on buying one at the end of the week.

I just want a modern basher and a occasional racer when time permits . I also like beeing a little different & don't like running a common racer like a B4. or 22.

The choice that i have decided on is the Atomick V2MR, Losi 22 ( only because I have a 22T & am really happy with it now) & Schumacher Cougar Dirt edition .

Price wise the Atomick is around $70 cheaper than a 22 from my LHS and $100 cheaper than the Schumacher from my local dealer

My biggest worry is durability. I have read that the drive shafts are weak??

Is this true or is it a stout buggy. I really love the comments that the rear generates a lot of grip which is what i'm after.

Cheers

[kaiser]

it's stout. i'm having driveshaft issues but they are still working.
the car is pretty cool and very robust.