55 replies to this topic

[legomuppet9]

My differential has arrived and I have added it to my fast car. The handling is much improved and it has increased the speed through the corners. Unfortunately the straight line speed has decreased a bit but if you drive it round a twisty circuit, your time will be considerably faster
Pictures are in my Flickr photostream (in my signature).
I will make an LDD file for it, and can share it if requested.

[Hopey]

legomuppet9, on 14 December 2012 - 01:42 PM, said:

My differential has arrived and I have added it to my fast car. The handling is much improved and it has increased the speed through the corners. Unfortunately the straight line speed has decreased a bit but if you drive it round a twisty circuit, your time will be considerably faster
Pictures are in my Flickr photostream (in my signature).
I will make an LDD file for it, and can share it if requested.

How have you fitted the differential? If it's one of the new 3-stud-wide 28 tooth diffs, you typically drive it with a 20-tooth double bevel gear, resulting in a 1:1.4 gearing down. If you don't compensate for this, it'll be slower (but with more torque). The diff itself won't introduce any significant amount of friction/drag when it's going in a straight line; you should be able to gear it up more (or down less, I'm not sure what gearing you've got already) and get the speed back.

Edit: I just had a looksie at the photos, and you do still have a 5:1 reduction, so I'm not sure where the speed's gone. Could just be friction in the extra gears; perhaps try a silicon lubricant?

Also, changing the drive wheels is an easy way to play with the effective gear ratio; i.e. increasing the diameter of the wheels by 50% is equivalent to adding an extra 1.5:1 gearing up.

Edited by Hopey, 14 December 2012 - 02:06 PM.

[DLuders]

It looks plenty fast to me:

[legomuppet9]

I think its mainly just my batteries, which are weaker, the difference is hardly noticable tho.

[DLuders]

@ legomuppet9:  Are you using Rechargeable AA batteries, or new Alkaline batteries?  The rechargeable ones will only deliver 6 x 1.2V = 7.2V or so to your motor, while new Alkaline AA batteries will deliver 6 x 1.5V = 9V.  The difference in Mechanical Power is seen in Philo's graphs below.  There is a substantial difference between the "Version 1" (v1) Power Functions Receiver and the new "Version 2" (v2) Receiver:

       

Edited by DLuders, 14 December 2012 - 02:54 PM.

[legomuppet9]

i have a v1 receuver and i use alkaline batreries.