Boardnamics CNC Motor Mount w/ Idler Tensioner

After seeing such interest in idlers for motor mounts, I decided to set out on my own to produce a mount that would make idlers more mainstream. What I provide is a little different from what I have seen. The idler is a tensioner as well. Moving the idler in the slot is what changes the center distance required for the belt.

With this design, you get the benefit of non slippage w/ an idler, with the compatibility to fit ANY motor size. This will fit any bolt pattern as big as 6364 sk3’s, to small 42mm size motors without an issue.

This mount is made to be run with Caliber II style trucks, preferably 10" ones. The clamping pressure is supplied by 2 perpendicular M6 set screws. It is also angle adjustable to provide the needed clearance for your setup. The idler is made with 2 608rs bearings clamped with an M8 bolt.

Dimensions: The clamp piece is 50mm diameter, 3/8" thick. The arm is 1/4" thick, 64mm wide, and 148mm long.

The mount’s are machined out of heat treated 6061 T6511 aluminum. This makes them considerably lighter than steel and acts as a much needed heat sink to keep your motor running cooler.

You’re probably wondering what belt to use with this mount. When I start production shortly, a 12mm HTD5M belt WILL BE INCLUDED. I calculated the clearance, and the following gear ratios are supported for a 325mm belt: 107mm wheel: 40/16, 40/15, 40/14 97mm wheel: All these^, 36/18, 36/17, 36/16 90mm and below: Everything listed above, 36/15, 36/14

There are more ratios possible with a longer or shorter belt. I am thinking of selling 320mm and 330mm belts to accommodate a lot of ratios.

In the picture, some of the hardware isn’t stainless steel. If I get enough interest, I will go out and buy in bulk quantity all the necessary hardware in stainless.

I am located in San Diego, California. I would be willing to ship internationally. My price would be $40 per set with some discounts for those who buy more two or more.

Anyways, yeah that’s the plan. Leave some feedback like constructive criticism and let me know if any of you are interested! I will answer all question about the mount. Thanks[poll type=regular max=1 public=true]

  • Not interested.
  • Interested in 1 set.
  • Interested in 2 or more sets. [/poll]

That looks awesome. I’ll give a pair a try. Have you thought about Paris clamps?

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I don’t have any Paris trucks yet. Something I will look into though. They’re tricky by the looks of it, not as much room to clamp to

Why wouldnt it work with a longer belt if you used a bigger gear ratio?

(I just dont understand, not trying to sound rude)

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Now that I think about it, a longer belt would work. I calculated everything based on what I deemed most popular, 36t spur and 14-16t pinion. It is hard to make a mount that can fit really small, and really big ratios. What do you classify as a big ratio? 36/18-20?

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Haha i think @longhairedboy uses 25t - 15t so thats kind of the opposite. Id say 32-44t wheel pulleys are common along with 14-16t motor pulleys.

Amen to that… I have been toying with mounts for a year in Fusion 360 and still havnt got it 100%…

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Yeah, they are little tough to work with. I used a pair of Paris 195’s with the @psychotiller RIPBA motor mounts and they are lush. I think Paris trucks ride better and hold up better than Caliber trucks, just my opinion.

Maybe look at Aliens Paris rings for there motor mounts.


16/32 on kegels baby


Nice work! I am glad to see this becoming a thing

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Nice project! I would like to see more pictures with motor, wheels, pulleys, belt and idler in action. :slight_smile:

This looks really nice! Good work.

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Will it work on 6374 motor with 13/40 gearing 107mm?

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With a 320mm belt, yes it will. I am thinking about selling 2 different belt lengths to fit people’s options. I am trying to target the main ratios people use the most though. 320mm and 330mm covers most.

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Do you have enough clampingpower with just the setscrews tightened on the trucks?

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I can’t get it loose. You have to really torque them down and use a quality 3mm hex. I orientated them 90 degrees of each other on flat spots of the truck.


A 30mm idler pulley is optional but a bit large. You can find 27mm OD bearings with a 8mm ID. Not a bad option for some with the room.

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I was thinking about this a year ago in my thinking i was trying to make idler spring loaded for automatic tension … never got to do it …U have me thinking about it again…

Great job love it

Thanks :slight_smile: Just trying to bring something a little new to the table. Idler’s that are adjustable I haven’t seen much of.

@Lionkev55 I keep throwing this at the screen but nothing happens, can you help? :stuck_out_tongue_closed_eyes:


Any chance of including 15mm T5 belts also? :stuck_out_tongue: would we need two bearings, I think they are 7mm wide each? What do you think ?

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