Simulator project 3DOF + heave + acc/brake + traction loss = 5DOF

First of all I would like to inform that this will be a long project as it is besides building the simulator is connected to three major other projects and issues, namely

• finishing of the 35m2 room in the basement where the simulator will be placed
• building a 72m2 garage for my daughters family
• waiting for our present Samsung 46” TV to be obsolete next year when the main channels in Finland transfers to DVB-T2

Although I have built a lot of stuff and also have electronics and Arduino as a hobby I am a complete rookie when it comes to simulators so I also have to search for a lot of information and one excellent source is this forum.

As a retired engineer and a grandfather to a seven year old “gamer” I thought that building a simulator would be technically challenging and when ready it will certainly make my grandson a more frequent visitor at our house.

As many of you here my goal is to build the simulator at a reasonable cost. As the project will take some time I have time to search for feasible solutions and economical parts. In my garage I have enough tooling for the project and machinery - a lathe, a vertical mill and a MIG welding machine - so parts fabrication should not be an issue.

As one big money hole are the gear motors I first intend to make a pre-study of some truck wiper motors.

After reading a lot of wiper motor stuff on this site and other information sources I decided to test two wiper motors,

• a Mercedes-Benz Sprinter Bosch wiper motor
• a Peugeot Expert (= Citroen Jumpy) Valeo wiper motor

I sourced the wiper motors from a breakers yard for this initial testing. According to information found the Bosch wiper motor from 1996 or earlier should have been fitted with a metal gear but to my dissapointment this was not the case. The Valeo wiper motor from 2000 was constructed as seen on pictures - dual worm gears and a two stage reduction. Although with plastic gears this should in my opinion be stronger than a one stage solution.


Tomorrow I will dismantle the Valeo wiper motor in order to see its condition and also at the same time isolate the ground connection from the motor body.

Opening up the Valeo wiper motor showed that it was in good condition except for the wire insulations that cracked when bending the wires. Because of that I just cut the wires as needed for dismantling.

Removing of the motor brush plate was the most difficult operation. In order to get the plate off without damage I had to,

- remove the mounting glue around the wire connection pieces
- grind down the two mounting stud heads
- when carefully bending off the brush plate also bend off the mountings under the brush plate around the two mounting studs - this can be difficult as seen in the picture where I had to unmount one clip and cut the other one.


When the brush plate was removed the following modifications were done

- the yellow overheat protector was removed and the mounting points on the plate soldered together
- the negative trace soldered at the point were I had to cut it when dismantling the brush plate

The negative connection is marked in black, high speed positive with broken red and low speed with continuous red.

For remounting of the brush plate I had to tap two M3 holes.

The collector was also cleaned with fine 400 grit emery cloth and the gaps gleaned with a “file” made from a hacksaw blade with the teeth sides grinded flat.


When assembled three new wires were soldered to the brush plate connection points and the plastic caps refitted and filled with engine grade silicone. Now I just have to wait for the silicone to cure.

Although the MB Sprinter wiper motor was fitted with plastic gears I decided to examine it a little bit closer. When opened up I noticed that the ground isolation on this motor would be really easy to do. The only thing needed was to remove the brown overheat protector and solder a wire to the foil going to the ground brush.

Things I didn’t like on this wiper motor was the use of a spring washer to fix the position of the output axle - guide difficult to remove without breaking it.

The big disappointment with this wiper motor was that it can’t be run in reverse - it is very noisy and the brushes are arching. So this wiper motor has to be skipped.

The silicone on the Valeo wiper motor had cured so I tested it a little bit

- runs fine in both directions
- runs 58 rpm in CW direction and 52 in CCW direction - a little bit slower that I had hoped for.

I have to test how turning of the motor housing affects the CW and CCW speeds and see if I can get them equal without any unwanted side effects. I will also make a quick test bench with variable load and wiper motor arm so I can make some measurements of the motor torque, current draw and heating.

Forgot to ask question in the previous post.

I have some rough ideas on how I will design the movements except for the heave that probably needs more power than a wiper motor can deliver. Thinking about spring or gas spring assistance?

But the question to those of you that have more experience of simulators - what would the absolute minimum movement in mm and speed mm/s be for a working heave on a Formula 1/Dirt simulator?

Grateful for hints based on experience.

Thank you for your info and link - had not noticed it.

Then some new findings...

I made a wiper motor arm with multiple fixing points 45, 55, 65 and 75 mm from output axle center and a quick test bench of some tubing, flat bar and nuts and bolts.

Unfortunately already when loading the mowing flat bar with my hand the toothed cone connection of the wiper motor arm started to slip. Obviously this type of connection is not strong enough when increasing the load.

I will modify the output axle and wiper motor arm mounting hole to something like this before I can continue.

I also ordered a couple of Monster Moto shields to be able to set up a more controlled test bench. The Arduino I already have and for testing I will run the setup from a car battery.

You actually summarize all the reasons why I first want to make some quick performance tests on the Valeo wiper motor before is start to sketch up a possible simulator frame. Measuring the torque, under load speed, current draw and motor heating should give me a better knowledge of what is possible and not possible with a wiper motor.

I will have look on SimCalc when I have motor data. For design of the simulator I intend to use Fusion 360 where I also can check movements, forces and flex of the frame.

Using the milling machine I modified the wiper output axle and milled a matching hole in a flat bar. After I had bended the flat bar to run free from the motor mounting bolts I drilled this time fixing points 35, 45, 55, 65, 75 and 85 mm from the axle center.







When mounting the motor I noticed that the arm could not rotate as it touched the mounting plate so I had to mill down the fixing points on the wiper motor by 2 mm.

Now I could mount everything in the quick made temporary test bench.

I did some preliminary tests with this setup although I could not make a optimum position for the arm angle as the motor runs full turns. When I get the Monster Moto shield I think I also add a potentiometer setup to be able to run the motor in a 120 degree sector and optimize the arm angle.

In my test setup the moving bar where the car jack is hanging is 100 cm long and the arm connection rod is at the middle. The wiper motor arm hole at 7,5 cm from the center was used.
The car jack weight was 7,9 kg. At the point where the angle between the rotating wiper arm and the connection rod is 90 degrees the current was highest - about 12A. Stalling the motor increased the current to about 19A.

Under load the rotation speed of the motor dropped from 58 to 50 rpm CW and 52 to 45 CCW.

Next I will make some rough calculations from these figures and continue when I can control the test setup to better match actual use.

Valeo wiper motor torque test and calculation

On test bench the load arm length is 0,8m and the load is 77,5N which gives a torque of 62Nm.
The wiper motor is lifting the arm at 0,42m from the pivot point that gives a lifting force of 62Nm/0,42m = 147,6 N. This force is generated with a wiper motor arm of 0,075m so the motor torque is about 11,1Mn.

Electrical calculation based on the current at the same rotation point as the previous test = 12A.
Motor running 6000 rpm, gearbox 1:100, worm gear efficiency estimate 50%.
Motor power to hp (12V x 12A)/746VA = 0,193
Electric motor torque (0,193 x 7 121)/ 6 000 = 0,229Nm
Torque at gearbox output 0,229 x 100 x 0,5 = 11,45Nm

So both approaches ends up with about 11Nm.

Stall current of 19A gives a stall torque of 18,1Nm.

Are my calculations giving a correct ballpark torque for the Valeo wiper motor? If they are correct it seems that it would be possible to make the basic 2dof with a motor arm of maximum of 45-50mm.