Building a 4DOF from the SK3 kit provided by Simukit

Hi all,

I am a flight simmer and would like to build a motion sim to enhance the flight experience. I have read several threads and realized that it is a time consuming process, and take a fair bit of dedication get a build to work well. So to make thing a little bit easier for myself I decided to buy the kit from Simukit and build it by following their instructions. Since some of our members, @jjanu , @axenic have already done this before, it gave me the confidence to try out this solution.

I should said that I do like many other complete commercial solutions (racingCube, njmotion) but I thought that the Simukit parts are generic enough that if I would like to build a 6DOF from it in the future then that will also be possible.

So I have placed the order two weeks ago to Simukit for their 3DOF 400W kit, the SK3 frame kit, and an extra 400W kit for implement traction loss. Today I have received all the three packages and I would like to start a thread to document my built process. Hopefully if I run into a problem then some member could help me to over come it. And if the thread can serve to help someone else then that will be great too.

Fingers crossed ....

Stargazer

For those who are interested, the cost of the three kits that I bought was:

1. kit SK3: $799 euro
2. kit 3DOF 400W: $1199 euro
3. shipping cost for 1. and 2. : $552.08 euro
4. kit for traction loss 400W motor and accessory: $277.89 euro
5. shipping cost to USA for 4. : $100.56 euro

Total cost in US dollar including PayPal fee: $3527.19

Yesterday I spray painted the frame so that it won't look too bland. Then I went a head and hook up the power supplies to the chassis and power it up at the end.

The power supply suppose to convert from 110V AC input to 24V DC output. But when I check the output with the voltmeter, it only show 20V. Would any body know why this is? In my case both brand new power supplies gave the 20V output reading instead of 24V.

@jjanu @axenic did you have this problem? Also I don't see how one can secure the power supplies to the chassis at all, do you have a way to secure the power supplies?

Another odd thing that I found was with the motor crank arms. They are not pre-drilled so that one can just hook it up to the other joint. Each crank seems to have a line of small indentation markings for drill holes. May be it was left to the customer to decide how long or short the crank arm suppose to operate. This approach doesn't work for a newbie like me because I have no clue as to where the drill supposed to be made. Also if the user doesn't have a drill press then this could be hard to get it right.

Could somebody please give me some help? @jjanu and @axenic what did you do for these crank arms?

Stargazer,

Following the recommendation of my contact at Simukit for my model of sim and load I needed to drill my cranks at the center indent which is at the 4th hole from one side or the other. I didn't use a table drill; a hand-drill did the job but I was constantly verifying my angle to make sure I was vertical while drilling. Use a quality drill bit for metal of the exact diameter of the screw so there's no wiggle once assembled. A special attention needs to be given to that part of the installation since the crank assembly will have to endure a huge torque and load, back and forth. Once the cranks are mounted to the motors and everything is well tighten the ball-joint need to rotate without effort. If you feel resistance when moving the ball-joint, give a little slack to the nut on the outer side of the ball-joint. I didn't test the power supplies output voltage before launching the system but I had no problem. These psu's are built to output the amp and volt that they're required to provide. So don't worry. Just make sure that your 15-amp 120 volt electric line that you will plug your sim in is not loaded with any other appliance, not even a light. Keep that line completely free and dedicated for you sim since there are going to be peak loads when the motors are highly solicited. And you don't want your breaker to jump every time it happens. Do yourself a favor and buy a Kill-A-Watt digital electric meter that you plug into the outlet. It costs about 30$ on Amazon and it tells you exactly how many volts and amp your sim is pulling from the line. I have one and I'm very pleased with it. You just plug your sim in the device.

Make sure to perform several motion tests with Simtools and the Simukit platform before adding your cockpit onto it. That will allow you to see if everything works well with the base before going any further.

You can watch my vids to follow the steps that I performed:

Step 1


Step 2


Good luck and let us know how it goes

Thank you @jjanu for the tip on how to drill the crank hole. I have also sent the question on the crank drilling to Simukit and here is the reply that I got from them:

"Hello,
yes it is you who must drill the cranks

it depends on the weight of the pilot + steering wheel + pedal + playseat
5cm if the weight is greater than 130kg
5.5cm if the weight is less than 130kg

Bien à vous "

This is good information to know and I wasn't able to find it anywhere easily.

With regard to the power supply voltage of 20v instead of 24v, Simukit sent me a picture of an adjustment screw on the back of the power supply which one can tune to the desired output voltage.

I was away on vacation until yesterday so there was not too much progress.

Today I drilled several holes into the frame Rio help secure the power supplies and the saber tooth controllers. This process took a fair bit of time for me and I broke a drill bit in the process.

I don't know why Simukit doesn't pre drilled these holes to make it easier for the user. There was also no supplied screws so I ended up having to use zip ties instead. A temporary solution I will replace them with proper screws when I get them.

I also did the wiring for the arduino and the saber tooth. I soldered the connection wherever I can to make sure there is no loose connection somewhere. At the end I also use gorilla glue to secure the arduino connectors. The whole process took all the morning.

One thing is that all the instructions are in French. I learned a little bit of French while living in Montreal,Canada. I can imagine others may have some difficulty following it. Simukit said the English instructions is in their to do list.

Another thing I found is that the power supply cannot be adjust to 24V by tuning the potentiometer as previously indicated by simukit support. 20V is its max and it only goes down from there. I am not sure why and I have no idea if this will effect the sabertooth operation or not? Could @jjanu or @axenic confirm the output voltage on their systems? Thanks.

Is there a 110V / 230V selector switch on the PSUs ?

@ausieSim I was looking for it but I could not find it.

If there were a voltage selector, it would be a red switch, usually on the metal side of the PSU

@ausieSim as you can see from the picture, there is no switch. I wonder if this psu can auto detect the voltage by itself? Clearly from the label it does support both 110v and 220v.

Hi, sorry for the delay, I see only now your posts.
The PSU can auto adjust from the input. The 20/24V diff is more of a concern IMO. The little potentiometer does nothing ?

For the crancks, I drilled them at the 5th hole, which was enough to move a 300kg load (Simukit calculations). I did this with metal bits on a lowcost vertical mont for my drill.
Be aware that one of my cranck were not rightfully pierced, and I had to adjust the hole to attach it on the motor axe.

If you need some help to translate part of the manual, do not hesitate to PM me.

Edit:
Also, BIG warning, as it cost me a 3 weeks delay and some more money...
Can you measure the heigh of the two gears that are provided to rotate the potentiometer from the motor ?

Simukit said they areviewed their design after I pinpoint to them there is a BIG flaw in the design.
So : heigh should not be around 2cm (0.25in).
If so, I remade them myself and can share you the blueprints, if you have a 3Dprinter (or somebody who can print them for you).

This is very important, as you will have to place the gear early before beeing able to finalize your test.

If you still go with the old simukit gear design, and your motor go on a full turn, the bolt of the cranck will hit and destroy the potentiometer, its mount, and maybe the gears...

@axenic I have emailed and also made call to Simukit but so far I have not heard from them about the 20v problem yet. I am hoping that it was some simple setting that I have missed. Until I heard back from them I don't want to turn on the rig yet.

About the crank I will drill on the 5th hole as you have suggested.

I just measured the potentiometer gears and they are about .59inch height or 1.5cm. Does this sound right to you?

@axenic what was the size of the drill bit that you used for drilling the crank?

So I finally got a reply from Simukit with regard to the 20V output and they are as baffle as I am. But they said that 20V will still work with the sabertooth so I can continue with the testing until they figure out the 20V problem.

Feeling brave, I downloaded the arduino software, sabertooth library, power up the rig and try to run the arduino sketch.

The arduino IDE has no problem seeing the arduino micro board and it is on COM3. The sketch was compiled ok but when I tried to upload it then it just stuck in the uploading state for a long time (see the screen shot). At the end it gave an upload error message. I am now completely stuck. Would somebody know what could be wrong with my arduino?

Hi stargazer !
The bit should be the same width as the bolt.
You should drill with an 10 mm bit. Try to use some vertical handler, to add the fewer play possible.

Once done, place a bolt on the newly pierced hole in the crank, place the crank on the motor axe, and try to rotate it a full turn. (you cannot place a bolt between the motor's axe and the crank, as It won't turn anoymore, but keep the crank aligned).
If you can rotate it without having the head of th bolt hitting the small gear, you are good. If not... you will want to change them.

The other point troubling me are the little screws used to tighten the gears to the axes. Again, try to make them collide. If they touch... you will want to change them.

Theses two points are important : yesterday, I had a miss-contact and one of my motor went crazy. It would have break everything (again) if I hadn't change the design.

Finally, about the arduino:
Be sure to run it as administrator (right click, run as, admin).
Be sure to have selected the right arduino type. (micro) (Tools : boards : Arduino/Genuino Micro)
Be sure to use the 1.8.5 Arduino version.
Use a usb2 port.

I finally found out what was wrong with my arduino uploading : I was using the wrong board. Instead of arduino "micro" I was using arduino "nano" for board type. One problem fixed.

But there seems to be no lack of problems for the project, the next problem was with the motor cranks: on some of them the holes of the crank did not line up with that of the motor. So I had to do some more drilling in order to be able to connect the crank arm to the motor. See pictures.

I also managed to drill the holes on the cranks (at the fifth mark as recommended by @axenic ) so that it could connect to the upper joints.

The next thing to do is to buy simtools and start doing some testing with the rig. This will be a major milestone for the project ... if it works.

That is a great looking 3dof! What was the name of the Rollercoaster that you were using in your test video? That looks like a good one!