Compact Motor Mount and Longbuild build

phomann

10 W
Joined
Mar 11, 2014
Messages
77
Location
Melbourne
Hi,

I've started down the road of building an Electric Longboard (for my son). I have an Alien Drives motor mount that is beautifully made but is a bit too long. Also I want to provide a bit more clearance between the motor and the board.

HomannMount.jpg


My setup is going to be two SK3 5055 motors using the Alien Drive pulleys and wheel mounts, along with a 6S battery made up of two 3S 5000mA/h batteries.

I've tried to make the mounts as compact as I cam. As it's a twin setup, there is provision for a support bar that sits between the two motor mounts. Below is what I've come up with. Over the weekend I'll cut them out of 12mm aluminum plate on my Taig milling machine.

Cheers,

Peter
 
Last night I milled the keyway slots into the motors.

I spent quite a bit of time trying to remove the shaft from the motor housing. It is held in by two grubscrews which are obviously loctited in place. They wouldn't budge so I had to mill the slots in place.

The challenge was how to hold the motor half so as to be able to mill it on the machine. In the end I put the back shaft on the motor and suspended the two shafts between a pair of V-blocks. I need to pack up the front V-block to get the shafts parallel to the table as the rear shaft is a larger diameter than the front shaft.
MillingKeyway.JPG


The tricky bit was locating the centre (highest point) of the shaft once it was in the V-blocks. Also there was no way to trial fit the key without removing the motor of the V-blocks. On the 2nd motor I had to refit the motor onto the mill as the slot was not deep enough. It tool a while to get realign it on the V-Blocks but it went without a hitch.

KeywaySlot.JPG


KeyFitted.JPG


In the end, it all turned out OK, and I now have the 12mm pulleys mounted.
PulleyFitted.JPG


Cheers,

Peter
 
My Son and I have also been making the longboard from scratch as well. We used 8 sheets of maple veneer. It still need to be varnished but is looking good. I'm hoping that we won't need to use any risers under the trucks if at all possible.

LongboardPress.JPG


We clamped the bag as shown above by folding the end between 3 pieces of wood, rather than use the sealing tape as supplied with the bag kit. Using the wood and clamps is much quicker, less messy and produces a more reliable seal. This was a trick my sister who is a cabinet maker taught me.


LongboardCutout.JPG


Cheers,

Peter
 
Hi Ben,

Thanks for that. Yes, the number of teeth in contact may be an issue and the proper belt tension will be critical. Also it is one of the reasons I made provisions for a brace to run between the left and right motor mount.

Cheers,

Peter
 
Great job!

Was that stone heavy enough to get a curve? I can't really tell from the pictures.
 
NICE BUILD SO FAR, LOVE THAT YOU ARE MAKING YOUR DECK!

I personally don't think the key-way is required! The motor shaft inside most brushless motors is held in place by a grub screw seated onto a flat spot. If its good enough to hold the shaft in place inside the motor it should be sufficient to hold a pulley? thats my logic...

I use one grub screw, plenty of thread locker on shaft & inside the pulley bore hole, my motor pulleys won't move.


You will be able to achieve appropriate teeth-in-mesh if you go with 15T-36T with 64.2mm centre distance. Actually you can go 14T motor pulley and still be ok, however anything lower 13T motor pulley won't be suitable at this centre distance and you will experience more cogging when accelerating hard or braking. It will still work, but not as good.

The cross brace is a great idea where you get that from? I can also see you have a nice extended bump to protect your wheel pulley teeth! GOOD IDEAS! :)

Do you have a single bolt/clamp? its hard to see? I recommend not clamping on two parallel/adjacent faces. The motor mount could still tilt/twist, unless it is a super tight fitment on the truck hanger.
 
Hi,

The pulleys came with a key so I used them. If I had pulleys without I would have done what you suggested.

The gear ratio I'm using is 12:36 so I might be heading for some trouble. The wheels are 90mm Abec 11 Flywheels. If necessary I will try 15 tooth pulleys.

I figured that the cross support will provide a bit of rigidity and help keep the motors parallel to the truck axle. Also it is positioned to help against the motors being struck by curbs, etc.

There is a single bolt clamping the mount that goes across the top in the diagram. The mount is split and the bolt clamps the split. One blue line is the centre of the split. The other is the bolt centre line.

Cheers,

Peter
 
Over the weekend I spend some time making the motor mounts.

The mounts consist of two parts, the Truck Mount part and the motor mount part. Initially I made them out of 4mm Perspex and 12mm Corian. I did this so I could check the fit. Both materials are very quick to machine on my small Taig CNC Mill.

Below are the images of how they turned out.

1PerspexMotorMount.jpg


2CorianTruckMount.jpg


3TestFit.jpg




The test fit showed that they turned out as expected. The next step was to make them out of aluminium.

Cheers,

Peter
 
I then turned my hand to making 2 sets of mounts for the dual 50mm setup.

As can be seen, they turned out pretty well. I designed the mount so I didn't have to use any risers under the trucks. Time will tell if there is enough ground clearance.

4DualMounts.jpg


5DualMounts.jpg


6DualMounts.jpg


6_2DualMounts.jpg


7Clearance.jpg


My next step will be to varnish and finish the longboard itself , then work out how to neatly mount the electronics to the bottom of the board.

Cheers,

Peter
 
I had slippage with my compact motor mount. Your mount would be easy to fix if it's too close. Looks good.
 
onloop said:
Some solid looking motor mounts there!
GREAT WORK!

Yes, they are a lot more solid than they looked in the drawings. :)

Cheers,

Peter
 
Hi Guys,

I looking at my enclosure for the 120A twin motor ESC.

Has anyone looked at using a 120A/150A 24V relay for switching power to the ESC? I'm thinking it might be worth considering.

Cheers,

Peter
 
I have been running the 12/36 gear ratio for a couple hundred miles now using 5055 320kv motors and have no sign of belt wear, before that 5045 450kv for 50-60 miles. I usually cruise around 15mph, but the 320kv will top out at about 22mph and the 450kv went over 30mph (scary fast). I'm about 190lbs, if it will hold up to me it should hold up to your son.

As for esc I'm using hk150 esc, and when testing, unlike previous esc, there is no amp draw when switched off at the esc. I have left the battery plugged in for weeks and just used the esc switch. I did kill a battery once by not switching off after I drained them... might check that since a relay to support the current these motors are rated for is really big.
 
Hey just curious, what cutting tool did you use to cut the motor shaft? Did you use an endmill? I assume carbide?
 
Hi,

Yes it was carbide, but it could have been HSS as the shaft is not hardened.

Cheers,

Peter
 
Hi,

Progress has been a bit slow lately.

Today I managed to get the Grip tape onto the board. I had been thinking about the design for a while .

The design I came up with seems quite appropriate.

ElectricGripTape3.jpg


Cheers,

Peter
 
About the size of an X-acto knife along with a few sharp blades :)

It was hand cut.

Cheers,


Peter
 
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