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Mid-motor touring cars. Legit faster or fad?

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Mid-motor touring cars. Legit faster or fad?

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Old 09-06-2019, 09:17 AM
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Hopefully the industry will standardize on the "Mid Pulley" designation as several manufactures are now using. It's a much more appropriate name.
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Old 09-06-2019, 11:42 AM
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Hmm, since I’m currently making the moves to get back into the hobby, I was going to sell my old TC3 since I already bought a new chassis, but MAYYYBE, I should just keep it in case shaft driven cars become a thing again.

But seriously, someone even made a “mid-pulley” kit for the Serpent 4X Pro I just purchased, which is not exactly the most popular chassis right now (but I have my reasons )... What else from 10-15 years back has the potential to come back around?
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Old 09-06-2019, 03:07 PM
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Originally Posted by TurnNBurn View Post
Hmm, since I’m currently making the moves to get back into the hobby, I was going to sell my old TC3 since I already bought a new chassis, but MAYYYBE, I should just keep it in case shaft driven cars become a thing again.

But seriously, someone even made a “mid-pulley” kit for the Serpent 4X Pro I just purchased, which is not exactly the most popular chassis right now (but I have my reasons )... What else from 10-15 years back has the potential to come back around?
TC foam ?
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Old 09-06-2019, 03:28 PM
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Originally Posted by DavidNERODease View Post
Hopefully the industry will standardize on the "Mid Pulley" designation as several manufactures are now using. It's a much more appropriate name.
I looked up the definition of mid-motor a long time ago. It is described as a motor that is mounted in between front & rear axles. What is wrong with going by the definition as given?
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Old 09-06-2019, 05:06 PM
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Originally Posted by jag88 View Post
TC foam ?
Oh I wish... I go way back to the pan car days. I hate the thought of having to glue tires if I don’t feel like buying premounts... but, it is what it is.
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Old 09-06-2019, 08:16 PM
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Originally Posted by 1spunspur View Post



This is Japan Express of Alex design.
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Old 09-06-2019, 08:31 PM
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Originally Posted by 1spunspur View Post
I looked up the definition of mid-motor a long time ago. It is described as a motor that is mounted in between front & rear axles. What is wrong with going by the definition as given?
Because the current "rear motor" configuration fits that definition as well. It doesn't really describe the drivetrain at all.
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Old 09-07-2019, 07:19 PM
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Originally Posted by jag88 View Post
TC foam ?
we are still running it in Germany at a few tracks.
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Old 09-08-2019, 12:03 PM
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Originally Posted by 1spunspur View Post
I looked up the definition of mid-motor a long time ago. It is described as a motor that is mounted in between front & rear axles. What is wrong with going by the definition as given?
The motor was already between the axles so calling it mid motor when it already was doesn't say much about the change. The equal length belts is one of the major reasons for the new design but I guess the pulley was already "mid" too so I don't really have a valid point but I do like mid pulley better because it hasn't been used to describe a chassis very much - unlike mid motor.
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Old 09-08-2019, 08:17 PM
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does the rotor in a motor create a resistance to twist? Like a gyroscope. does moving it closer to the middle of the chassis change the way the chassis twists?
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Old 09-09-2019, 12:10 AM
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Originally Posted by Bar View Post
Loved the Schumacher SST Axis Pro back in the day

Fantastic car despite being offroad-based (like the mid-front-motor Street Weapon it was competing against, btw!)... I had two at some point, one for stock one for mod... Then came the Axis II with the center rod and not quite the same thing.

The thing is, bitd mid-motor TC was an afterthought - now it's really a conscious choice...
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Old 09-09-2019, 12:35 AM
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Originally Posted by Bry195 View Post
does the rotor in a motor create a resistance to twist? Like a gyroscope. does moving it closer to the middle of the chassis change the way the chassis twists?
Technically, yes. I think the offroad guys take advantage of that by switching between 3 and 4 gear gearboxes so they can change the orientation of the twist.
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Old 09-09-2019, 06:05 AM
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It's funny everyone's focusing on this equal-length-belt part, when really one can make a traditionnal MR (mid-rear ) motor car rear belt engage *about* the same time as the front one... all it takes is playing with the diff inserts in the bulkheads. I most often do this with my cars when get skitterish, looser rear, tighter front. Works perfect.

Now: Is there any engineer in this thread who can tell us what is the main element of these MM designs that makes them feel so different when running? Lower polar inertia with more mass around the yaw center, especially as these masses are rotating like a gyro? Different flex (Christian is hinting at it)? something else? I'm struggling to believe that equal-length belt is the main one...

Thanks,
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Old 09-09-2019, 07:03 AM
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Originally Posted by Lonestar View Post
It's funny everyone's focusing on this equal-length-belt part, when really one can make a traditionnal MR (mid-rear ) motor car rear belt engage *about* the same time as the front one... all it takes is playing with the diff inserts in the bulkheads. I most often do this with my cars when get skitterish, looser rear, tighter front. Works perfect.

Now: Is there any engineer in this thread who can tell us what is the main element of these MM designs that makes them feel so different when running? Lower polar inertia with more mass around the yaw center, especially as these masses are rotating like a gyro? Different flex (Christian is hinting at it)? something else? I'm struggling to believe that equal-length belt is the main one...

Thanks,
Paul
I don't think the equal belt length is the only thing, but I do think it plays a large role. For one, the drive train is more free as you don't have to run 1 belt disproportionally more tight than the other. I still run the front belt slightly tighter, but the difference between F/R is lower and overall the tension is lower. Billowing of the belt is also much more even and this is going to cause a difference in power delivery and friction at speed.

I stand by my statement that Increased rear flex is a benefit as this gives the car more on power steering and off power stability. I find it interesting that everyone came out with these flex adjustment splines for the rear of the car, yet no one is really using them. I just read a post from Felix Law, (who designed the Medius I believe) telling a fellow racer that they found that the "new" set up is by using only the furthest most forward screw on the motor mount and the most rearward screw on the mount, no rear spline screws. (Basically just mounting the motor mount close to the center of the chassis) I know of a really fast XRAY guy that ran the ZT chassis and pretty much did the same thing. Awesomatix guys around me are using the spline only for weight; We run our car with only motor mount screws and the most rearward screw on our spline loose.

I have been collecting racers' preferences for a while, and to me, it all seems to be pointing to this being a main advantage. I have observed that this much higher amount of flex achieved, when combined with the lower pendulum effect of the car caused by the motor being placed further forward creates an increase in stability and predictability on the edge of traction. Sure, you could increase the flex in a more rearward placed motor, but the weight of the motor being further back makes a pretty big difference in how the car finishes the corner. Older designs, "swing" the rear around the end of the corner, while the center mounted spur gear cars seem to have a more efficient pivot closer to that center. Therefore, when you increase the flex on a "rear spur/motor" (which you are limited in how much you can) car you end up possibly with a car that may be a little unstable on power.

When you combine the 2 effects (and with some cars even further with longer arms), the cars are much more stable than the previous counterparts. Simply put, they are easier to drive.

As to people wondering why we are reverting to this, I believe that chassis design has lead us to a better overall package. In the past, centrally mounted, equal length drivetrains did not have the flex in the rear of the chassis part down and the cars had far less power (Mike at Exotek with the Exo5 had it really close though!) The result was cars that did not steer as well as the rearward mounted spur gear cars with shorter arms.

FWIW, offroad has been doing this for a while as well now. The changes being even more extreme. 2wd buggies are now laydown transmission, mid motor, 4wd buggies moved their electronics forward and increased rear chassis flex in front of the bulkheads. 8th scale buggies have been like this for a while as well. I guess Cab forward bodies and electronics-forward designs are nothing new
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Old 09-09-2019, 07:27 AM
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The one thing I don't understand is the ridiculous flex in the front end of my Medius kit and there is no significant provision to adjust it. You can soften the rear but you can't stiffen the front
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