Mid Motor XXX-T Build...

[y2kgtp]

Well, some of the spy shots of the older Mid motor vintage stuff (and the newer X Factory stuff) got me thinking I could make one of these.



Got a Speed-T off eBay for 143$ shipped....DSM radio, Brushless motor\ESC, etc...the whole thing....gotta love snipe software!

Came with a silver body, but I like the blue better. I also had to put some off-road tires on it as the Chromie on-road tires
really made it not look like a stadium truck.





Flipped the Trans 180 Degrees, with the differential flipped as well inside so it still rotates the same direction. Stock spool has been replaced
with BfastRC diff rings and balls.







Rough cut the chassis out, so the motor & spur clear......even the stock diff cover fits as well. I had to put a tiny notch in the
motor mount to get it to clear, but really minor. The nice thing here is that the trans fits perfect in the lower arm mount, with the
dogbones lined up exactly as before.....no suspension suprizes as really the suspension geometry has not changed.




Trans is 180 degrees, so motor has to run in reverse. No Problem. It's a sensorless motor, and can run just as well
forward, as it can in reverse. I'm hoping the same is true for some of the sensored ESC\Motor combo, as I have to
run Mod class with a sensorless setup.....not that is a bad thing, but I would also like to try 13.5T SuperS tock class
as well...(Sensored motor requirement)

I have not decided if I am going to run the battery in the stock position, or across the chassis. I could do it either way.
If I dremel out a section right behind the steering servo, I can get a battery pack to fit fine here running a stock position.

My main concern next is to fabricate a upper trans brace, as I lost this when flipping the trans and shock tower, as I have some flex
in the lower chassis. Still trying to figure out the best way to get this done.

Maybe I should just cut a sheet of G10 or CF and have people really guessing what this might be?

[slazzaro]

WOW!!
Very good idea!!
I have a XXXT MF2 and would like to try the same modification!!
I have a spare chassis and a spare motor plate, so I could easily go back to the original layout..
Why you want to install the ESC in line with the battery/motor/servo?
If you installed it on one side the battery would fit without further modifications, I think.
About the tranny brace.. in effect there is need for one.
You could try to use the motor plate/cover holes to fix a plate (I would use CF) between the motor plate and the vertical wall of the battery compartment.
this would make the chassis not symmetrical, but now I can't figure anything else..
You could design and cut a specific motor plate (out of CF or aluminum) including an extension to be fixed to the battery compartment wall.
How much is the gap between the motor plate and the battery compartment wall?
Could you take a picture from above?
Bye!

[y2kgtp]

The ESC is just sitting there as it had to go somewhere while I was looking for ideas, as I have not un-soldered the motor. I have not decided if the battery will mount in line with the chassis, or across the chassis. Inline will prob net some better handling, over the cross chassis battery position, I am guessing. I will just have to remove some material right behind the servo so the battery can slide forward a bit more. The only drawback to this is I have little room to play with for weight adjustment down the line. if I have the battery mounted across the chassis, I can have 1-2" of room to play with to get the balance how I like it.

For the trans brace, I don't have much side wall to work with as I dremmeled it down to clear the motor plate. This is just my first trial chassis however. I was trying to keep from having to run a top plate, but I might have to for this one. some sort of plate or a connecting rod to connect the top of the transmission to the top of the servo mount might do it.

[y2kgtp]

1 other thought I had, was trimming down the rear motor guard, and then bolting that to the chassis. The Speed-T & Desert Truck both have a rear guard different from the other XXX-T's as something is mounted to it, such as the Desert Truck cage, or the Speed-T wheelie bar.

[slazzaro]

I would stick with the inline battery.
You can always tune the weight distribution putting some leads (in pairs, same amount at left and right).
Anyway in my experience with hipower brushless systems on 2WD cars you always need some lead at the nose, and You are already doing it by moving the pack forward.
Why do you want to bolt the motor guard to the chassis?
If I'm not wrong in the Losi Speed-T & Desert the motor guard is also used to install a small fan over the motor and for the wheelie bar...
I will think about a nice solution for the brace...
Bye

[y2kgtp]

I would stick with the inline battery.
You can always tune the weight distribution putting some leads (in pairs, same amount at left and right).
Anyway in my experience with hipower brushless systems on 2WD cars you always need some lead at the nose, and You are already doing it by moving the pack forward.
Why do you want to bolt the motor guard to the chassis?
If I'm not wrong in the Losi Speed-T & Desert the motor guard is also used to install a small fan over the motor and for the wheelie bar...
I will think about a nice solution for the brace...
Bye

I'm moving alot of the weight forward, with just the motor now in front of the axle, that should help with steering under power, I would think. Factory,
they don't have a fan mount for the motor, but I'm sure people have installed them as needed. (Desert truck is just a 540 12T motor)

If I install the motor guard to use as a trans brace, I'm gonna have to run the battery across the chassis, due to lack of room.

[y2kgtp]

I think the motor mount as a brace might be the cleanest idea.

Top of the mount


Bottom of the mount. I can use the 2 circled areas to mount screws threw the chassis to
secure the Trans, as it would connect to the top and bottom of the trans case. Red lines
are probably what material I would remove to make it fit as well. It uses really thick screws
here as it held the wheelie bar in place, so it should support the trans fine.

[Bongo Fury]

Strongly agree that you need to come up with a good brace setup. The portion of the chassis where you have cut down the battery sides is already a less than robust part of the XXX chassis. They tend to develop fatigue cracks in that area over time already. Which means that there are plenty of chassis available for this mod, I’ve got a couple myself! Also I would be concerned about the T plate.

As the goal I believe of a mid mount is to centralize the mass, reduce the rotational inertia, I would suggest considering a saddle pack battery arrangement. Yes, a pain in some ways (with reduced lipo battery brand/model options) but it seems to me that you have pretty much already crossed that bridge. A plus is even more flexibility in battery position, and perhaps more room for the brace.

Are you aware that X-Factory ended up adding another idler gear to the transmission to reverse the motor direction (relative to the chassis)? Apparently without that as the motor accelerates it tended to unload the rear end, and since there is less weight on the rear end to begin with, less traction. They claim that reversing the motor rotational direction provided a significant increase in forward traction.

Good luck!

[y2kgtp]

Now, which way is the pinion on the X Factory truck spinning with the 4 gear trans? Is it toward the back, or the front of the truck?


I'm gonna keep stick style Lipo, as well....I have them already!

And this is a budget build. I have 143$ + 20.50 for the diff kit....That's the truck, radio & Brushless setup. Not intended to keep it a budget build, it just turned out that way by chance of eBay.

[markt311]

I believe they just moved the motor to the other side of the transmission when they went to the 4 gear. I've talked to Paul from Xfactory about it for hours, he will talk all day about RC car physics. He said the old 3 gear would cause the rear of the car to unload because of the motor rotating against squat of the car under power. X factory has a new version of their buggy coming out, it might give you some more ideas. The best part about talking to Paul about RC's is he brings out a bunch of prototype stuff to drool over, he had about 5 different tranny cases last time I saw him

[y2kgtp]

I believe they just moved the motor to the other side of the transmission when they went to the 4 gear. I've talked to Paul from Xfactory about it for hours, he will talk all day about RC car physics. He said the old 3 gear would cause the rear of the car to unload because of the motor rotating against squat of the car under power. X factory has a new version of their buggy coming out, it might give you some more ideas. The best part about talking to Paul about RC's is he brings out a bunch of prototype stuff to drool over, he had about 5 different tranny cases last time I saw him

That must be cool to play with that stuff all day. I'm just doing mine to see if I can make it work, with as little modification to the truck as possible. I'd really like to know which way the motor is rotating in both the 3 gear, and the 4 gear transmission. Mine is a complete 180o flip, so I will be running the brushless reversed of normal rotation .....why I was asking which way the X60's run

[y2kgtp]

Which of these is the 4 gear? I think the truck does, as I found it in an article about a rumored 4 gear being tested.....

[Group B]

Can I ask a stupid question?

What is the advantage of having a mid-mount motor & trans?

[y2kgtp]

Can I ask a stupid question?

What is the advantage of having a mid-mount motor & trans?

My reasoning behind it is prob less technical than X-factories

I don't see any advantage of the motor behind the real axle. All it does is create leverage
for the truck to wheelie more on power. With the weight now in front of the axle, this puts
more weight on the front end. It should steer better under power as I see it.

+ no one else really has a Mid Motor Losi Stadium truck, do they?

[Bongo Fury]

Yep, the truck has the 4 gear, you can see the bump in the tranny case for the extra idler gear. The motor is positioned the same as yours, but rotating in a standard direction, as opposed to your need for opposite rotation. On the 3 gear they bring the top shaft out of the other side of the tranny to address the motor rotation issue, which is why it is flipped compared to yours.

The mid mount setup, which is a very old idea btw, is intended to move the mass closer together, reducing rotational inertia. Thus the car turns easier, and stops turning easier too. Quicker reaction, pretty standard race car stuff.

Sadly you are not the first mid Losi, while uncommon, I’ve seen pictures of several posted in various places. Some are just converted nitro trucks, suggest checking out a Losi nitro truck for ideas.

I’ll check, but I’m not sure how you reverse the direction of a sensored brushless set up. It’s not as easy as just flipping wires like with sensorless I don’t think.