Belt tightening for the steering wheel

After putting together a wheelbase with htd 3m 20t to 72t pulley there is a need to say that the friction required for tightening the belts is plainly insane.
Motor is a car fan motor which is pretty heavy, roughly around 2 human fists size. I measured around 0.75 Nm back when it was direct drive. But that was too weak and motor would get hot after half an hour of use.
Now I used an Timing Pulley Distance Between Centres Calculator website and it says that about 7cm shaft to shaft is an ok length. Doesn't really work
After tightening it real good it was able to get north of 1 Nm but any more force and the belt start skipping like mad. The belt is 96t 288mm htd 3m 9mm wide.
Now am I really doing something wrong here or is all that crazy friction a must? Maybe adding an idler pulley would help?

From my experience, you really need 5m pulleys if you're trying to get decent torque. This is what is used in the T300 and T500. They have longer teeth which helps the belt grip better.
However, if you're willing to start over again though, you should probably look into using a "vee" belt system, like Fanatec use.
I haven't used them myself, as I've invested so much time and money into using 5m timing pulleys now. But the vee belt are meant to provide a smoother feel, and they way the belt grips the pulley is a lot better.

Also, something you might want to consider using is idler pulleys. All commercial belt drive wheels use them, however they add unwanted resistance, so the wheel will be harder to turn, even when the power to the motor is off.

Also, make sure that there's no sideways movement between the front and back plates of your build, if that makes sense. To do this, you need "columns" going from the front to the back of the your build. It's hard for me to explain this but look at how the Fanatec CSW is build on YouTube. It will help .

Thanks for the help!

I saw a post where it was recommended to use htd5m, it was probably yours .
The wheel is built a little differently from the most diy wheels. There will be a picture in this post.
The main problem here is that smaller pulley is so small that a 1 or 1.1 cm hole (size of the motor shaft) cannot be safely drilled through it. So it is held in place by super glue. I got lucky that one portion of the motor shaft is ~0.8 cm and the pulley was drilled to that size. But the pulley flew off 2 or three times now when pushing it too hard.

I thought about maybe drilling a hole through the shaft, perpendicular to it, and putting a screw through it. Same holes would be drilled through the pulley if it survives. The width of the protruding part of the small pulley is 13 mm and motor shaft is around 10 or 11 mm so...

Will get an idler or two to try and maximize the contact area between belt and small pulley. For now the wheel produced around 2.3 Nm at ~60% duty cycle and performs like a thrustmaster TX, maybe around 5% better. Did a test with a guy from openffb chat.

I guess when you say that one part of the shaft is 0.8cm, you're saying that there's a flat on the shaft?
If so, you can use a pulley that has grub screws fitted. They're about £3 on eBay, you just have to wait about a month. Grub screws have worked for me in the past, as long as they're used on a flat surface. They're no good on a completely round shaft though.
Hopefully putting idler pulley will help you.

Also, if adding extra components is within your budget, your could make a dual belt system, as shown in my picture. It'll put less strain on the motor and the motor pulley will be less likely to slip.

Also, when you're finished. Make sure you bolt down your encoder. If you leave it to hang freely like that, it'll lose position. Only slightly, but after a 20min race you'll be about 5 degrees out.

Your setup looks... Futuristic

Unfirtunately the whole motor shaft is flat. The way car fan was mounted is like... There are those two "sticks" close to the motor on the shaft. Fan hub slides onto shaft and the thing that is machined at the end of the shaft serves to enter a ring between the slightly wider part and the hub. Do you have any suggestions on modifying the shaft? Maybe reduce its diameter or make a D shaft like you mentioned.

Oh and forgot to mention the V belts from fanatec and Indonesian wheels. A friend who is experienced in the field gave me advice not to use flat belts because they will have some slip.

I have one more questions. Do you feel the belt teeth on the wheel. I can feel the transition between teeth on my wheel which is kinda annoying.

And hey we have the same ball bearings

I wouldn't like to give advice on modifying the shaft. My past attempts at that kind of job have failed. Sorry.
It's hard to say about feeling the belt teeth. I think the notchy feeling that comes from the motor is going to be more prominent than any notchy feeling you get from the belt. Can't say for certain though, as I've not tried different pulley types.

Hi! I have both 3M and 5M belts in use and 5M feels clearly more notchy.

Your jumping problem may be because of flexible base... It really needs to be rigid when belt is tight. Also there might be a chance that your motor 'turns'... in picture you can't tell how many anchorage points are there to base (only 2 on back side)?

Actually you are spot on.
Whole construction was bending in an arc like shape and the motor was rattling because it didn't have 3rd screw used. This was an attempt to make it work without using a drill.

Tried idlers, without any success, belt is too short to fit an idler in there...

I have 2 really really thick square plywood boards that will be horizontal structural support, like almost every other diy wheel out there. If that works and speed is great than it may be a good idea to add second set of pulleys like in Chris setup.

Got some epoxy to glue that pulley to motor shaft Real Good!

These are plans for the future, as I'm currently developing for a stepper motor base which kinda works for now and there are other more important thing to do for now. There will be a post in these forums soon when I make a video. So main purpose of the dc wheel is to have a reference point for development of stepper
and also have 2 setups for some real time competitions