Carrera Bently LMP final drive conversion

Squeezing out those last few tenths

Carrera Bently LMP final drive conversion

Postby wixwacing » Fri 18 Jul, 2008 11:51 pm

Some of the Carrera models from around the year 2000 had major problems with their gearing. For small club and local use the gearing was too tall and you were lucky if the model managed to wind itself up by the end of the straight. On big circuits and large club tracks that are mostly straights and sweeper curves the models are fine once up to running speed. The momentum will carry them through most bends and the motor is ready to go after high corner exit speeds.

The problem was the final drive gear ratio and the large diameter tyres. The overall final drive showed the models to be lethargic out of bends and, with minimal braking, hard to stop going into the next bend! So what to do? I have toyed with the problem for some time and the only feasible solution is to lower the gear ratio. Aiming at 3 : 1, I carried out the following modes.



Image



The first item to purchase was the Ninco F1 rear axle. This is a nice wide axle with a 24z contrate on it. It's main attraction is the contrate's small diameter. Those who are familiar with Carrera rear ends know they fit a tiny 64 pitch contrate and pinion which requires little clearance under the body. Normal 27z contrates require extra room and the Bentley upper body and chassis simply do not have the clearance. It would be necessary to doctor the chassis and body to get them to fit and to be able to screw the body fully on.

The next item to be had is the Slot.It 8 z pinion. The best feature of this is its large diameter. This allows it to mesh with the contrate quite easily and not to allow too much side play and consequent poor meshing. Secondly, at 8z it gives me my target ratio of 3 : 1!

The motor was removed and the pinion fitted. The motor was then glued back into place. Next, the axle bushes were transferred onto the Ninco axle. The wheels were carefully removed from the heavily knurled Carrera axle and glued in position on the new axle. The axle was then fitted to the model and with a low current applied to the motor, the rear axle cover plate was screwed down. Be careful screwing this plate down as tightening it fully causes the axle bushes to tilt and to put excessive drag on the final drive.

Next, after an application of petroleum jelly to the gears. I decided to put it through the hoop at The Red Team's home track. On the track it was an instant transformation. The only initial problem was the lack of grip. The rear tyres were sanded lightly and then cleaned with pure hydro-carbon. Putting the model back onto red lane saw the transformation complete. The model had developed a big heap of manners and was a cinch to drive. Driving harder still I eventually managed to clock a best lap of 7.061 seconds. No cobwebs on this little baby!

The model circulated in total comfort in 1.1 to 1.2's and finally I accepted that it was now a hot contender. The rear end was quiet and the track performance was well mannered and predictable. Most deslots were of the half oversteer variety, the model would slew roud before leaving the slot telling me the guide was working well but perhaps a little balast or a change of rear tyre might help.

I've been fiddling on and off with this model for a few years now, disappointed with its out of the box performance. But now it can hold its head up on a busy track.
Image

When I'm not racing slotcars,
I'm out in the back yard, burning food!!

When I win, it's because of my talent, not my car or my controller!
User avatar
wixwacing
Marshal!!!
 
Posts: 1906
Joined: Thu 10 Jul, 2008 8:22 pm

Return to Tuning Tips

Who is online

Users browsing this forum: No registered users and 1 guest

Untitled Document
Image hosted by Photobucket.com
Image hosted by Photobucket.com

Image hosted by Photobucket.com

Image hosted by Photobucket.com

Image hosted by Photobucket.com
Image hosted by Photobucket.com

Image hosted by Photobucket.com
Image hosted by Photobucket.com

















































































































































Image hosted by Photobucket.com

cron