Made a diff checker
 

Seen the original from Monaco RC I must say it is a bit overpriced. The idea of using an ammeter to measure force is not new to me as I have used that idea from the start of my heated oil bath break in bench for nitro engines so this is nothing more based on an electric motor and an ammeter.

I promised some guys to make some so I went online shopping in Asia, all it needs:
- a smal 6 volt 300 rpm geard motor
- 5 digit ammeter (is also used by the Monaco RC version)
- a case
- a switch
- a small 5v regulator
- cheap 7mm hex wrech to modify
- some wires

The electronics is simpel: wire -> switch -> 5v regulator -> ammeter -> motor
Between the switch and the regulator I mounted a diode so wrong polarity will not harm

I thought to be smart by using cheap Chinese steel 7mm hex wrenches to cut of the 1/4" hex part and drill an hole through it but the guys now how to hard metals, so no go....
Lucky I also had ordered the Tamiya style wrenches which was easy to modify for the 4mm motor shaft mount so that can be used on the wheelnut of car.

The adapter for the diff itself was made on the lathe from 10mm aluminum

Without the work it is about 20~25 dollar worth of parts and some time to put it all together.

https://cimg6.ibsrv.net/gimg/www.rct...8ce1a14fa1.jpg
https://cimg0.ibsrv.net/gimg/www.rct...f678278b1e.jpg
https://cimg3.ibsrv.net/gimg/www.rct...b2caf09039.jpg
https://cimg8.ibsrv.net/gimg/www.rct...3c1ad98231.jpg

I bought one and realized it could be made very easily. I have the new Monaco. I dont think it has an ammeter. I think its simply a motor with a known amp/speed and the change in velocity provides the variable that indicates current in a lookup table.

This sounds technically more complicated than just measuring the amp draw. I think the Monaco is just what Roelf did with a fancier box - and actually its box is probably the most expensive part. :)

I have not seen the Mocaco but if it also starts with a low number w/o any load then for sure it is an ammeter. If the meter shows zero w/o load then they have adjusted the meter to show 0.

This is the one:
https://www.dx.com/p/0-36-led-5-digi...3#.XKHoyNhcKUk

Comes in several colors.

The motor:
https://www.dx.com/p/chihai-motor-ch...1#.XKHqOthcKUk

The regulator:
https://www.dx.com/p/super-mini-dc-d...4#.XKHqxthcKUk

The box with a very tight fit for all parts:
https://www.dx.com/p/btoomet-2pcs-wa...9#.XKHrHdhcKUk
A package of 2 is almost the same price as one ;)

And easy to modify:
https://www.dx.com/p/mini-hexagon-nu...7#.XKHsathcKUk

Using a torque meter is indeed beter for all systems because you will use a universal standard scale which will not be different among several different products. I know many years ago there was such a torque tool to measure offroad diffs Never know what hapened with it but it probably wasn't a succes or too expensive.

This is only to compare and if you use the same tool and within the production all the same spec materials (basically the motor) you can make it a setup option to note.

Niftech made one for onroad 1/12 - 1/10 pan cars in the early to mid 90's that utilized a miniature torque wrench. I will see if i can find the ad.

now how about a vacuum pump for shocks? My arm gets tired when I have to use the one I have.. ;)

Busy with it!

Did find a vacuum pump and a vacuum meter on DX.com. Could manage a plexiglass tube of 60mm with a 3mm thickness. Have 60mm silicone O-rings and large round aluminum and plastick (PE) for the base. I need to choose which material to use and ge an air valve (fish tank shop)

It will have a center 6mm pin to hold a diff or an holder for the 4 shocks.

Here the parts:

https://www.dx.com/p/DC-12V-Electric...5#.XLW2kdhcKUk

https://nl.aliexpress.com/i/32917944...ce82428bed08-2

Thanks for sharing. I wouldn't buy a diff checker, but I would build one.

Bruce

@mushromed

Here a sneak peek:

https://cimg2.ibsrv.net/gimg/www.rct...59c629db5e.jpg


https://cimg9.ibsrv.net/gimg/www.rct...54036b11da.jpg

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I would rather buy a vacuum tool that removes all the air from the diff rather than some checker. Regular rebuilds cost less than one checker. Having several diffs built at different CTS, I personally see this as a vanity tool while it may provide consistency in theory with numbers, the best method is to rebuild as the data is presented in variables that often times are irrelevant. My point imho is that if you open a diff to top it off.. change the oil, if it is leaking replace bad seals, outdrive, and or, case I believe this will provide more consistency hard or soft. After all the engineers that developed the oil are in theory correct.

Removing the air bubbles from a diff is pointless. You will trap air in it when you seal the case, and the moment you spin it up, it emulsifies the air back into the oil.

The experience as with shocks is that more or less a drop of oil can make a huge difference. Going a small step lighter in oil but using a drop of extra oil can make a diff and a shock harder. So a meter will check if you did it right. In case of good drivers I think it is wise to see if your change is established or was is wrongly done.
It is like you want more toe-in and screwed it up with a toe out because you did not measure it..

Great work! I had no idea I needed a new tool/project until now!
Stupid question: How (and when) do you use this if the scale is in current and not a torque value? Do you just check the difference between front and rear diffs?

You can check stiffness of different diffs. The valor is not important, the important is the difference between 2 numbers (ex: 1600 is stiffer than 1400)