R/C Tech Forums - Made a diff checker

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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.

Quote:

Originally Posted by Bry195 (Post 15423541)

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

Quote:

Originally Posted by sbd (Post 15423676)

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. :)

its more complicated conceptually but its simpler from an application perspective. My point is that Roelof is doing it the right way. In the long run an ammeter accounts for wear and changes in the mechanics.

if a motor spins at 1000 rpm and draws 1 amp and that means 1nm of torque at the motor and a gear ratio that results in 10nm when the motor spins 500 rpm it delivers potentially half the torque.

if you use a torque transducer to measure the torque at each rpm (or an ammeter) you can do it once to calibrate the tester. The processor in the tester takes the rpm and spits out the scaled torque based on the calibration that was done at the factory.

Roelof is very smart and what he made is just as clever. My only point is that its probably superior than an off the shelf solution. It really doesnt matter. Its just talk but Roelof has helped me out in the past and i was commenting on how i think he is doing it correct.

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.

https://cimg8.ibsrv.net/gimg/www.rct...937640ade.jpeg
I made my own years ago and cost me less than $9.00 and you probably got everything you need already at your house.

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.

Thanks for the parts list, I’ll be giving the diff checker a try. I’d also be interested to try a shock pump if you make a working design.

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

Bruce