New twin motor longboard project "Now running"

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Re: New twin motor longboard project

Post by torqueboards » Sep 21, 2013 10:20 am

Nice! Can't wait to see that mount and the awesome welding skills.
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Re: New twin motor longboard project

Post by recumpence » Sep 21, 2013 11:57 am

Vapology wrote:In stead of making her breakfast in bed? For shame, for shame! I could never get away with that :)
Well, we have been married for nearly 21 years. She never likes breakfast in bed.

What my wife likes is when I do dishes and other housework for her. If you subscribe to the "Love Languages" theory, her love language is "Service". She likes being waited on.

At any rate, as for the project, I only did about 20 minutes of welding. But, the truck took nearly an hour to cool down. You do not want to quench aluminum to cool it down. Aluminum gets brittle if cooled too quickly. The slower it cools, the more stable it is.

Oh, the welds look pretty poor actually. The presence of the steel axle through the aluminum tube created some crap in the weld. No big deal. I will grind it down smooth anyway.

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Re: New twin motor longboard project

Post by recumpence » Sep 22, 2013 9:59 am

Sorry for no pictures yet. I was hoping to have the motor plates done before posting pictures so you could see the completed drive truck. :)

I have the evening at home tomorrow night. I am hoping to fabricate the motor plates then and post pictures. Actually, I will post a comprehensive step-by-step picture log of the entire process of bringing raw aluminum blocks to completed parts.

I have one question for you guys, though;

What wheelbase would you recommend? The motors will be in front of the rear truck. The deck will be dropped. So, the rear portion of the deck will need to be relatively narrow to clear the motors at full lean. So, this limits foot space. Therefore, I would like the wheelbase to be somewhat on the long side. But, I want it to still corner well.

Anyway, I could go as short as 29 inches, or as long at 36 inches (though I know 36 is really long).

What are your thoughts?

Oh, also, wait till you see the deck. It is more of a chassis than a deck in that I am TIG welding it together from 6061 box section aluminum tube with decking on top. This will give me a strong deck with lots of room to hide components between aluminum tubes. It will also allow me to shape the deck in any way I want. For instance, I will be arching it up a touch to clear the rear wheels and motors at lean and I will be giving it varying concave based on foot location and other factors.

I am thoroughly enjoying this build!

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Re: New twin motor longboard project

Post by LEVer » Sep 22, 2013 11:11 am

36 is not really long, sort of just middle for a longboard. I think Eboards shouldn't really be shorter than 30", cause it gets very twitchy at higher speed. In my experience, the two rear motors corners better than a one rear motor. I cant wait to see your build, seems like its gonna be EPIC.

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Re: New twin motor longboard project

Post by recumpence » Sep 22, 2013 12:57 pm

I have it layed out on the bench at 34 inches right now and that "Looks" correct.

Anyway, since I am welding it together, it would not be out of the question to alter the wheelbase after it is finished to accomodate something I had not thought of.

Oh, also, as for high speed handling (reduced twitchiness) I have the rear truck at a very shallow angle (I do not remember the angle at this point, I will check it and get back to you) for minimal rear steer and increased angle at front. I have adjustable plates. So, I can fine tune the handling to my taste.

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Re: New twin motor longboard project

Post by shortcircuit911 » Sep 22, 2013 1:53 pm

Sounds like it's going to be bad ass. I look forward to seeing the pics of the step by step process. I will be starting my motor mount this week out of aluminum, so it would be nice to see how someone else did theirs just to keep the ideas flowing.

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Re: New twin motor longboard project

Post by recumpence » Sep 25, 2013 6:24 pm

OK, finally, here are some pictures.

I was really hoping to post a long explanation of how all of the various parts were made. But, honestly, I just do not have the time. I took a huge number of pictures. But, I do not have the time to explain everything. So, here is the completed rear truck.

It consists of a Cindrich adjustable plate and 240mm truck that has been cut and extensively modified, TIG welded together, and assembled as you see here.

As explained earlier, the pulleys are not attached to the wheels. They spin on bearings around the truck. This keeps the belts in line. I have heard people post on this forum that belts tend to wear out faster than chains. Well, I can tell you that is NOT true if the alignment is correct. With correct alignment, a belt will last nearly forever.

Anyway, enjoy the pictures!

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truck1.jpg
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truck2.jpg
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truck3.jpg
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truck4.jpg
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Re: New twin motor longboard project

Post by sk8norcal » Sep 25, 2013 7:00 pm

looks good,

got a close up pic with the wheel pulley off showing the needle bearing deal?

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Re: New twin motor longboard project

Post by recumpence » Sep 25, 2013 8:31 pm

Here you go.

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Re: New twin motor longboard project

Post by Silenthunter » Sep 25, 2013 9:07 pm

Why you didn't use a regular bearing?

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Re: New twin motor longboard project

Post by sk8norcal » Sep 25, 2013 9:51 pm

he explained it earlier,
The reason for needle bearings is because the wheel adapters I am making consist of one inch ID tubing that runs into the wheel. The pulley will be pressed over that one inch ID tube. The bearing must fit inside the one inch ID tube and around the 3/4 inch OD truck axle extension. The only bearing that
will fit is a needle bearing.

matt, thx for those closeups,

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Re: New twin motor longboard project

Post by torqueboards » Sep 25, 2013 11:21 pm

Awesome setup! Nice machining skills.

What belt threading did you use and why did you use the 15mm width belt? Is the 15mm width actually needed? How do the 240mm long trucks ride?

Also for welding aluminum trucks to an aluminum motor mount, does it weaken the trucks? Did you reheat the aluminum motor mount to re-strengthen it?
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Re: New twin motor longboard project

Post by recumpence » Sep 26, 2013 9:07 am

The belt is 5mm pitch. It may be too wide. We shall see. The motor pulleys are 12 tooth. With low tooth count, added width is a good idea.

Aluminum get brittle when cooling if it cools too quickly. I welded the truck together and let it cool slowly. That allows the aluminum to cool without getting too brittle.

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Re: New twin motor longboard project

Post by torqueboards » Sep 26, 2013 10:01 am

How did you cool it slowly? Did you just let the air cool it down after welding? Ex. Welded it and just let it cool. Or did you have to heat it up and slowly lower it? Is that also the 15mm width belt? Is that the HTD thread or GT2 thread on the belt?

I was also going to go 15mm GT2 threading on one of my builds but decided it probably wasn't necessary. I'll end up going 9mm GT2 and to end up keeping all my setup with the same belt setup.
Awesome work. It's crazy seeing the totally customized work :D
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Re: New twin motor longboard project

Post by recumpence » Sep 26, 2013 12:47 pm

I welded the parts and let them cool slowly with a towel over them.

I run HTD belts on most of my projects. Here is some background on this;

I used to manufacture RC helicopters. Now I manufacture high end electric bicycle drive systems. I have used HTD, GT2, L, XL, and MXL pitches. I have used as small as 2mm pitch and as large as 25mm wide 5mm pitches. My experience has been that GT2 pitch profile is only higher holding than HTD in very small pitches at high RPM. At our low RPM with larger pitch, there is no discernable difference between HTD and GT2.

I went with 15mm wide because I am running a small 12 tooth motor pulley. That small tooth count requires a wider belt to prevent skipping. It is really easy to go to a narrower belt. But, this wide belt is pretty much guarranteed to not skip.

Anyway, the efficiency is lower with wider belts. So, I plan on testing 9mm width too.

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Re: New twin motor longboard project

Post by torqueboards » Sep 26, 2013 2:40 pm

Awesome Matt! So in your opinion for our application of using belts on electric skateboards. There is no real benefit to using a GT2 belt with an electric skateboard? Would the belt even last longer? There would be no better grab unless higher RPMs and with smaller pitch sizing. I was going to use GT2 belts on my setup but am thinking otherwise now if there will be no noticeable difference on a 5mm pitch for GT2. Is there a slight better difference or none at all? The price difference is not much if any. If there is a slight benefit I may opt for the GT2 belt still.

For 14 tooth, would you still use a 15mm belt and/or would 9mm suffice?
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Re: New twin motor longboard project

Post by recumpence » Sep 26, 2013 5:54 pm

For 14 tooth, I would say 9mm wide should be fine. Of course, that depends on the torque you plan to put through it.

If you can go to GT2 without much added cost, than why not? :)

I am extremely experienced with belts, but not with skateboards. So, I may be off on that.

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Re: New twin motor longboard project

Post by torqueboards » Sep 26, 2013 8:24 pm

What are you using to keep your drive hub inside the wheel?
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Re: New twin motor longboard project

Post by recumpence » Sep 28, 2013 9:16 am

Nothing. The hub slides onto the carrier (oversized portion of the axle) and the wheel slides onto the axle while keying into the hub. Once the nut is on, the hub is captured and does not need to be fastened to the wheel.

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Re: New twin motor longboard project

Post by recumpence » Oct 02, 2013 8:52 am

Little teaser update......

The wheelbase is 35 and 1/2 inches. It looks a touch long. But, I really want stability. Plus, the way the deck is laid out, it drops down in front of the motors. This nearly kills the rear 8 inches of the deck. So, I need as much room between the trucks as possible to stand. Also, with the 240mm wide trucks, the added length helps the overall proportions from a looks standpoint.

So, wait till you see this thing. It has an "Aircraft" look to it. You will see what I mean when I post pictures. :)

It will be a few days yet to get some decent pictures. But, rest assured, I will.

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Re: New twin motor longboard project (finished TIG welding p

Post by recumpence » Oct 13, 2013 6:20 pm

Hey Guys,

The fabrication continues. Unfortunately my TIG welder took a dump last week. So, I am waiting for it to be repaired. In the meantime I did some drive system testing. I ran the drive wheel against my bicycle tire to use it as a make shift dyno. The unloaded speed is 26.6 Mph. So, under load it should max out around 23 mph. That is plenty.

The startup torque is huge. I have no doubt it will be a beast to ride.

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Re: New twin motor longboard project

Post by recumpence » Oct 21, 2013 7:17 pm

Here are a few pictures of the "Deck". I finally got my TIG welder back and went to work immediately.

The deck top and bottom will be 1/8 inch thick carbon fiber/plywood laminate. The packs will be sandwiched between the top and bottom decking sheets. So, the overall thickness of the deck will be 1.25 inches with the packs totally invisible within that 1.25 inch thick deck. :)

It looks like the finished board will weigh in at 18 pounds with six 3S-5000 mah packs. I have no idea if that is light, heavy, or about correct for a board of this size with twin motors and this many packs.

Wait till you see how I plan to mount the two ESCs! :mrgreen:

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Re: New twin motor longboard project

Post by Murfix » Oct 22, 2013 1:16 am

I hope you'll like the handling of the thing. It's a very nice project.

I'm dreaming of having a 3D printer and the opportunity to weld (maybe even CNC). Then, the world lies at your feet!
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Re: New twin motor longboard project

Post by recumpence » Oct 22, 2013 7:10 am

The trucks are adjustable. So, the handling is adjustable to a certain degree.

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Re: New twin motor longboard project

Post by Murfix » Oct 22, 2013 7:20 am

Have you tried it yet? It seems to me that you could do a first test already!
Memo to myself: Screw it, just do it!
1 Apr 2013 - Start pre-engineering my first EV build!
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