EXTREMO - Scratch built 7kW billet frame scooter

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EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 03 2021 12:01pm

Hello,

I've decided to post my personal project still in design phase.

I was pretty amazed and inspired by the work done by alex_2d so I decided to work on my own design to be more affordable and easy to manufacture.

Frame dimensions, wheelbase and suspension kinematics have been calculated for best handling both on-street as well as off-road.

Key Specs:
  • Dual 72V / 3500W hub motors (7kW total power)
  • 72V 36Ah 18650 Battery Pack with 150A BMS
  • Dual 150A controller - 18 Mofset
  • Billet Aluminium EN AW-5083 frame and suspensions arms
  • Dual MTB air shocks (165mm - 41mm stroke) front and rear
  • 150mm wheel stroke (front and rear)
  • 11' wheels
  • Hidraulic dual-piston brakes with 160mm rotors
  • Approx 50Kg total weight
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I still need to select few components. I've read quite positive feedbacks about Nucular 12F controller and should be my initial choice too.

Hope you enjoy the project and follow-up with idea and suggestions.
Last edited by BigBlock on Jun 17 2021 10:36am, edited 3 times in total.
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by Chalo » Jun 03 2021 12:26pm

Seems like an awful lot of trouble and expense for a contraption that's not nearly as capable or comfortable or safe as a bike, and not nearly as lightweight or compact as a typical donut wheel scooter.

That looks to me like at least two hours battery endurance, in a vehicle that would not be fun for that long at a time. One-third as much battery would make for a more nimble, pleasant and versatile scooter, that still can go for longer than anybody wants to stand on it.

If you can only draw 50A max from your 72V battery, that's a 3.6 kW scooter. Maybe approaching 3 kW to the wheels if everything works optimally. Still plenty, but not 7 kW by any measure.
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 03 2021 12:37pm

Chalo wrote:
Jun 03 2021 12:26pm
If you can only draw 50A max from your 72V battery, that's a 3.6 kW scooter. Maybe approaching 3 kW to the wheels if everything works optimally. Still plenty, but not 7 kW by any measure.
I plan to start with a single motor - if not enough, I will then add the second motor later. Just want to understand if the extra complexity and weight is worth the extra power
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by SlowCo » Jun 03 2021 1:50pm

Nice project :thumb:
But isn't the trail too long/large for a scooter like this? It seems better to lengthen the front swingarm to get the axle at least on the steering axes. Or are you're dimensions/geometry based on a special kind of design?
Trail too large.png
Trail too large.png (48.25 KiB) Viewed 1603 times
Just an observation.
Good luck and enjoy building!

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 03 2021 2:24pm

I got 77mm of trail - I've seen some high-speed scooter going close to 95mm.... I suppose that anything between 50 and 80mm is a good banchmark for this kind of scooter with 11' wheels. Isn't it ?

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by SlowCo » Jun 03 2021 4:40pm

That's much less than it appeared.
And it will be fairly easy to fine tune later on if necessary. It's a fine balance between responsive steering at low speeds and stability at top speed. Again: great project and I hope you will update this thread with your progress.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by HTTR » Jun 07 2021 5:15am

Its not often that we get something this exciting in the scooter category. :bigthumb:

The influence of the Vostok is clearly there and I think you did a great job of simplifying some of it’s over engineered aspects. I really hope we all get to see this one come to life and am glad to support in any modest way I can.

It looks great so far in my books and would like to offer two cents of feedback as requested:

The thing that probably jumps out the most is the discrepancy between the agressive design, dimensions, and suspension system on the one hand and the power specs on the other. A 50A limit on a 72v battery is very, very low. For reference it is around half of that of the Dualtron Storm. I run what is not a relatively standard upgrade on my Dualtron Thunder with a 20s10p (samsung 40T), ANT MBS (400A peak) and a pair of 6F Nucular controllers. The Vostok 2.0 has stated spec of 500A peak :bolt: :bolt: .

The reason that there are no single motor systems in anything, but entry level scooters is because that configuration just cannot deliver power in the same manner. The original Rion Apex was the first and last such attempt and despite their race cars expertise, carbon fiber build in a super light chassis it barely equaled the performance of the half price / double weight Thunder. Sure the Vostok do its at the cost of incredible complications of the liquid cooling system and the Vostok 1 from all videos I have seen accelerates slightly faster than the Thunder and DTX but is by no means a “high performance” scooter … again from the videos shown.

Speaking of motors, seems that you are going for standard hubs and if so, you might want to checkout the 130/40 R6.5 originally produced to replace the square times from the Weped’s. They fit the thunder/ultra rims but as they are larger once mounted they do not work with all designs … just saying as they’d look really cool on your design.

Why dual shocks on the rear, it might be easier and cheaper to go with a single shock design like the Bronco 11 extreme.

Nucular controllers are among the best and offer a lot of configurability. The 12F is the right choice here but the waiting list can be of over a year. You should get your pre-order in asap and since there is no pre-payment or deposit involved make sure to order a pair so you give yourself some room to decide later down the road. The way it works is that you indicate your interest in buying and they issue you a waiting list number for your order and when your turn comes up you can pay for it and have it shipped or decline and they pass on to the next happy customer.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by HTTR » Jun 07 2021 5:21am

Chalo wrote:
Jun 03 2021 12:26pm
Seems like an awful lot of trouble and expense for a contraption that's not nearly as capable or comfortable or safe as a bike, and not nearly as lightweight or compact as a typical donut wheel scooter.

That looks to me like at least two hours battery endurance, in a vehicle that would not be fun for that long at a time. One-third as much battery would make for a more nimble, pleasant and versatile scooter, that still can go for longer than anybody wants to stand on it.
It's not really an either / or situation. A high powered scooter allows you to do things that you can't do with a bike or motorcycle particularly in cities or urban settings. For having tried a variety of different options, I have to say that the scooter is what works best with me and love to go on long rides. It's different. Not as safe, that's for sure and I would not go out without full protection gear.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 08 2021 6:30am

thanks for the feedback. That's exactly was I were expected sharing my project here.
HTTR wrote:
Jun 07 2021 5:15am
The reason that there are no single motor systems in anything, but entry level scooters is because that configuration just cannot deliver power in the same manner.
I agree. This is my first project of this kind thus I need to build a base point to asses my preferneces and learn how to improve. I'm definitelly convincing myself that I have to start with a dual motor setup and properly sized battery and controllers.
HTTR wrote:
Jun 07 2021 5:15am
Speaking of motors, seems that you are going for standard hubs and if so, you might want to checkout the 130/40 R6.5
I will be using 110/90-6.5 tyres but I will take a look to this 'bigger brother' option
HTTR wrote:
Jun 07 2021 5:15am
Why dual shocks on the rear, it might be easier and cheaper to go with a single shock design like the Bronco 11 extreme.
Thie air shock I gonna use are designed for MTB that have ususally a leverage of 2:1 - 3:1 - to get a 150mm wheel stroke on such short wheelbase you have to reach 5:1 ratio that requires a very stiff shock (high pressure on air chamber). When using two air shocks you can let them work at their ideal pressure (100psi) with a lot of flexibility to tune your SAG and ride height.
HTTR wrote:
Jun 07 2021 5:15am
Nucular controllers are among the best and offer a lot of configurability. The 12F is the right choice here but the waiting list can be of over a year.
I know. That's why I'm looking for something else with a faster leading time. I'm oriented to SABVOTON controllers that seems to provide good performance and plenty of configurations. Main issue I need to fix is the size and packaging under the foot board....
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 08 2021 6:57am

I got this OEM motor that should be a replacement part for the FLJ SK3 72V scooter;

It's rated at 3500W @ 72V and should have 60mm magnets.

Unfortunatelly it came without any spec sheet, so any more info would be appreciated.

Image

Wiring looks standard 3 phases BLDC with 3 hall sensors but without temp sensor

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 08 2021 7:25am

Any suggestion how much battery and phase current I can push on this motor (continous / max) ?
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BalorNG » Jun 08 2021 11:03am

Find it's no-load current and internal resistance and than you can make educated judgements... easy using a VESC.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by HTTR » Jun 08 2021 4:10pm

HTTR wrote:
Jun 07 2021 5:15am
Why dual shocks on the rear, it might be easier and cheaper to go with a single shock design like the Bronco 11 extreme.
Thie air shock I gonna use are designed for MTB that have ususally a leverage of 2:1 - 3:1 - to get a 150mm wheel stroke on such short wheelbase you have to reach 5:1 ratio that requires a very stiff shock (high pressure on air chamber). When using two air shocks you can let them work at their ideal pressure (100psi) with a lot of flexibility to tune your SAG and ride height.
HTTR wrote:
Jun 07 2021 5:15am

Thanks for the explanation. What model do you have in mind ?

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by HTTR » Jun 08 2021 4:15pm

BigBlock wrote:
Jun 08 2021 7:25am
Any suggestion how much battery and phase current I can push on this motor (continous / max) ?
If this is the one that comes from the Aliexpress "FLJ Official Store" then I saw a couple guys use it on a Thunder build with the same 20s10p (40T), AntBMS 300A so that would be 150A peak they are throwing at it BUT with phase cables upgraded to 12AWG high temp silicone ones and one when to 10AWG. Passing to these is on my to do list for this winter .... when I hope to get the Nuclear 12F to replace the pair of 6F I have.

Where are you located ?

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 10 2021 6:23am

I'm using this one just because I found quite cheep in a local bike store:

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 10 2021 7:16am

I 'm also working to a different steering tube design - the classic straight tube looks cheep and not in line with the overall style

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 12 2021 6:21am

I'm struggling to find the right space to fit the battery pack - It looks the best I can do with 18650 is 20s9p...

I would like to reach at least 120A per motor (peak) - Looking at Molicel P28A or Samsung 25S

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by Chalo » Jun 12 2021 8:07pm

Trust me that you won't be able to use 120A in the front motor. Amps are torque, and there's simply no way to stick down that much torque in the front unless you are going backwards.
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by spinningmagnets » Jun 12 2021 9:25pm

Easy burnouts can be fun a couple of times, but...the novelty wears off and it quickly becomes tiring and expensive to replace the tires frequently. Power is not acceleration.

Once you raise the power to the point where full throttle breaks the tires loose at all speeds, then any more power is a waste of available battery volume. Whatever extra room you may have in the battery compartment might be better used to extend range, but...the choice is yours. Fun project, though...

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 13 2021 5:06am

spinningmagnets wrote:
Jun 12 2021 9:25pm
Whatever extra room you may have in the battery compartment might be better used to extend range, but...the choice is yours. Fun project, though...
I agree. But you have also to consider that such scooter is a fun machine not intended for very long range. I prefer to save weight too.

Using the Molicel P28a the pack will have capacity of 25Ah, a peak power of 315A and a reasonable weigth of 4.1Kg

Going with an energy focused cell (Samsung 30Q) the pack will provide 27Ah with a peak power of 135A

Under normal cruising conditions how long you can drive with 25Ah ?? I hope at least 40-50 Km....
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by HTTR » Jun 14 2021 5:12pm

You always have the option to design the column to include the controllers, particularly for if you are using some Nucular 12F which are relatively small and that has the added bonus of providing more cooling and letting the battery breath a bit.

Am sure you considered 21700 batteries so will not go there.

40Ah (20s10p in samsung 20P) on stock thunder motors gets just under 98 km range (and still a bit left) of cool cruising, mostly on flat between 30 and 50 Km/h.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 17 2021 10:31am

I finally managed to fit a 20s12p that will give ideal balance between performance and capacity.

Using Samsung 30Q I will end up with a 36Ah pack and 150A BMS

Going with traditional layout will allow to spread the series connection by all 12 cells (150/12 = 12,5A) that should be managed with easier weldable nickel strips (0,15mm) without going with copper or copper + nickel sandwitch.

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by cheapcookie » Jun 20 2021 5:21am

I hope b- and b+ will be on one side of the battery, how much current are these controllers rated for ?

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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jun 21 2021 10:44am

what you mean b- b+ on same side ? They are the first e last rows of 12 cells.

The controllers are Fardriver rated at 150A max and 400A phase current. They are 18 Fets controller. I've not tried yet but they seems very well engineered.

https://www.aliexpress.com/item/1005002326822446.html
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Re: EXTREMO - Scratch built 7kW billet frame scooter

Post by BigBlock » Jul 20 2021 12:36pm

Just a quick update: I've completed the machining of the first batch of parts. A lot of work.... Always excited to see parts designed from scratch coming to life :D

I personally like the rough machine finish, so I think I will keep as is

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