Super Street Sensation (8448) - RC in progress

[Finntech]

This is my RC MOD for 8448. It is not ready yet, but I like to start this topic anyway. Hope it don't mind.

This is a great supercar, and I find out that it may not be too difficult to motorize it with PF-elements. So I want to give it a try.

I have added

Propulsion:

1 m-motor, goes well with gears 1, 2, 3, R, but it's not strong enough for 4 and 5. XL-motor is already ordered.

Steering:

1 m-motor to steering, 24 teeth clutch gear + 8 teeth gear. Steering wheel in cabin works

Gearbox

2 m-motors for partially remote controlled gearbox, 1 motor in both side, remote: 1+R, 2+3 or 4+5 and free position with all pairs. So when changing e.g. from first to fifth gear, you need to move the gear shifter manually. Dead simple system, works very well. One can think that is useless with only 2 gear + free, but it's so cool to change gear to bigger or smaller while driving!

Others:

1 battery box, easily remove

2 IR-receivers

2 remote controller

All the original functions are still working, suspension, convertible top, steering wheel, dummy engine, gearbox

Here is just a quick video, showing how the PF-elements are added. I will try to take a video of functions if somebody is interested, after I have changed the XL-motor for driving.

http://www.youtube.com/watch?v=igSChCkTA2k&feature=youtu.be

Edit: new video of driving, still m-motor and batteries not 100 %. You can hear me changing gears between 2nd and 3rd, and if you look closely, you are able to see it goes faster (obviously) with 3rd gear. In 3rd gear propulsion is louder as you can hear, but it sounds must worse on the video than it actually is.

http://www.youtube.com/watch?v=nPCWDZfivsQ&feature=youtu.be

Wheelcaps btw. are from 8157 (system formula), it is matter of taste but I think they look cool. They are easy to take off anyway.

Sorry I can't describe the functions very well, because of language. Continues, hope you liked this small sample.

Udate, pics (sorry about the quality, camera not good):

Update edit: pictures seems to be quite large, sorry, I'm helpless with photobucket and can not resize them smaller.

Edited February 1, 2012 by Finntech

[timslegos]

Looks interesting, keep up the progress.

tim

[Blakbird]

The original instructions for this model included a section on motorizing it with the old 9V geared motor. However, the motor was only intended to be run with the model up on jacks (no load on the tires). The gear ratios in this model were designed to run the engine from the wheels, not the other way around. You may be able to get enough torque to drive the model fast from the XL motor, but I think you'll destroy various gears and axles inside the model if you do.

I seem to recall that there were also instructions somewhere to put an RCX in this model which would also control the steering, but I can't seem to find them at the moment.

[trekman]

I built the 8448 up from spares which I had, and then added 4wd and a mid diff. Maybe it was due to the 4WD, but I found that the gear ratios were such that I did not drive well even from the XL motor. Fitting the XL was easy, when you kept the engine in the front, as there was space in the rear, but I found that there was a lot of crunching as it crawled along. It is a nice build. It is the transition stage before full studless came in.

[Finntech]

Well I hope that XL-motor won't destroy parts... is it really that powerful? I kind a believe that it will work fine, but let's see. Maybe some gearing is necessary, for build up more speed, since I heard that a XL-motor is much slower than m-motor.

After I completed the 8448 I actually added jacks for lifting the rear wheels from the ground, just like Blackbird mentioned, and ran the model like that... But it's quite boring in a long run, it is much more fun to actually drive the car.

I was surprised that only one m-motor was enough to move the car in a different speeds, I wasn't expecting that. I tried one m-motor setup with older 8880 also, but basically it didn't move at all. I guess it was because of 4WD, drivetrain on that model is not very smooth, even though it is very cool design. Maybe 4WD was really the problem, why Trekman's model didn't move well. My model is not crunching at all, of course that might be just because of less torque. Drivetrain keeps noise of course while driving, but it's not crunching, grinding, slipping etc.

[trekman]

Well I hope that XL-motor won't destroy parts... is it really that powerful? I kind a believe that it will work fine, but let's see. Maybe some gearing is necessary, for build up more speed, since I heard that a XL-motor is much slower than m-motor.

After I completed the 8448 I actually added jacks for lifting the rear wheels from the ground, just like Blackbird mentioned, and ran the model like that... But it's quite boring in a long run, it is much more fun to actually drive the car.

I was surprised that only one m-motor was enough to move the car in a different speeds, I wasn't expecting that. I tried one m-motor setup with older 8880 also, but basically it didn't move at all. I guess it was because of 4WD, drivetrain on that model is not very smooth, even though it is very cool design. Maybe 4WD was really the problem, why Trekman's model didn't move well. My model is not crunching at all, of course that might be just because of less torque. Drivetrain keeps noise of course while driving, but it's not crunching, grinding, slipping etc.

After the work involved in getting the 4WD fitted and it not moving as well as expected I ended up dismantling it. But it would be great to see you RC'ing and it working well. I do think that it is a very nice model, especially with the modular build.

[Blakbird]

Well I hope that XL-motor won't destroy parts... is it really that powerful?

Yes, the XL is powerful enough to twist axles even without any gearing. When you add the gear ratio on the 8448 between the motor and the wheels, I don't see any possibility of it not destroying parts. It will work fine on jacks just like the smaller motor, but it takes a lot of torque to actually propel a car that heavy at speed. The issue is not the power of the motor, it is the strength of the drive system.

[SNIPE]

Yes, the XL is powerful enough to twist axles even without any gearing. When you add the gear ratio on the 8448 between the motor and the wheels, I don't see any possibility of it not destroying parts. It will work fine on jacks just like the smaller motor, but it takes a lot of torque to actually propel a car that heavy at speed. The issue is not the power of the motor, it is the strength of the drive system.

I once added 4 pull back motors, a v14 engine and a 9v motor, broke 1 12 tooth gear and 3 or 4 10 tooth bevel gears .as a result.

[Finntech]

Yes, the XL is powerful enough to twist axles even without any gearing. When you add the gear ratio on the 8448 between the motor and the wheels, I don't see any possibility of it not destroying parts. It will work fine on jacks just like the smaller motor, but it takes a lot of torque to actually propel a car that heavy at speed. The issue is not the power of the motor, it is the strength of the drive system.

I see, you are saying that gears and axles should be stronger, not motor weaker. But still, what if I gear the motor up a bit for a little less torque? And maybe use lighter wheels instead of the originals, would that help? I'm also using 1,2v rechargeable batteries instead of 1,5v, so I assume that the motor provides less torque that way. I'm going to try it anyway, if I destroy gears and axles so be it... I want to see it myself. And I have spares.

Edited January 31, 2012 by Finntech

[Blakbird]

I see, you are saying that gears and axles should be stronger, not motor weaker. But still, what if I gear the motor up a bit for a little less torque? And maybe use lighter wheels instead of the originals, would that help? I'm also using 1,2v rechargeable batteries instead of 1,5v, so I assume that the motor provides less torque that way. I'm going to try it anyway, if I destroy gears and axles so be it... I want to see it myself. And I have spares.

You said your goal was to be able to actually drive the car in any gear. From that point of view, it will never work because the car isn't designed for that and the parts can't take it. You can drive very slowly by gearing everything down and probably be OK, but you can't drive fast in high gear no matter how big the motor is. Gear and axles are your weak points. Look at the results of trial trucks for evidence. If you really want a LEGO car to drive fast, the only way to do is put the motors right at the drive wheels, or have a very light car.

There's a reason none of the the LEGO Technic cars has ever been R/C. There have been some Racers, but they use special parts. Real R/C cars of this size use steel parts, and they still break regularly.

The new rock crawler is going to be R/C. We'll see how LEGO handles that. I suspect there will be some new parts involved to strengthen the drivetrain. But 8448 was only designed to spin the wheels on jacks. While you technically can modify it to be R/C, you will reach the limits of LEGO parts very quickly.

[timslegos]

Nice remote control functions. It is too bad lego parts cant handle more strain, i love fast cars.

tim

[Finntech]

You said your goal was to be able to actually drive the car in any gear. From that point of view, it will never work because the car isn't designed for that and the parts can't take it. You can drive very slowly by gearing everything down and probably be OK, but you can't drive fast in high gear no matter how big the motor is.

Making this model run fast with RC was not my target, but able to drive it in any gear, just like you said. I have now added XL-motor, and it drives very well with gears 1-5 (and reverse). I didn't gear it down as far I have understood what gearing means, I have one 16 gear in motor and second 16 gear in axle what goes trought gearbox (center). That said I don't know these things too well, maybe I geared it down accidentally.

I'm running the motor with 7,2V, so it seems to be quite slow. The car is definitely not going fast even with 5th gear, but it is good speed for model that size. And like I said, my goal was not to make it actually fast. I'd say its top speed is quite perfect to drive inside.

What pleases me most is the motorized gearbox, changing gear from 4th to 5th and back works very well while driving. It doesn't change speed much, but it works!

I will try to take good pictures and better video later.

[bmollema]

My attept resulted in 3 workable gears (R,1 and 2 (very slow driving)) but the rest will not move the car

See pics on http://www.mocpages.com/moc.php/290753.

Bernhard

[Finntech]

My attept resulted in 3 workable gears (R,1 and 2 (very slow driving)) but the rest will not move the car

See pics on http://www.mocpages.com/moc.php/290753.

Bernhard

Nice, I like it! It's cool to have remote controlled gears. I see you have used m-motor for drive, it is probably just not strong enough for rest of the gears. After I changed the motor to XL, it was slipping and crunching gears, but afer some tweaking (making connections stronger, finding correct gear setup between motor and axle) it worked fine with all gears.

[Paul B Technic]

I have just found this post and it has given me some ideas for adding a motor to drive the back wheels (off the ground) of mine. I am also going to look at adding a remote control for the gear box so I can control this.