Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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hicksi   100 µW

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Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 22 2018 4:27am

Hey Team,

As expected we have got as far with our build as we can without asking for advice.

Long story short, we got the build to a point on Saturday where we were able to test drive the scooter:

Set up:
GoPed BigFoot Scooter
800W 36V DC Motor (China)
36V speed controller (4 position)/(China)
X2 5S 18650 battery packs (Series)
11T front sprocket
74T rear sprocket

It may just be me, but I felt after the test ride that we were 'missing a trick' and the motor should have more to give. Low to Mid torque and topped out around 8-10mph. I've been looking at several videos online of similar builds. In particular retail scoots (urban scoot 800) and kids 800W quads, mini mx bikes etc... These things look ALLOT faster. Couple of questions to save my sanity;

1. Looking into the gearing i think we are geared way to high, running a 74T on the rear, if you look up spares for the chaos 800W scooter for instance it runs a 55T rear sprocket. I've not had much experience with these chinese DC 800W motors, but are they set up for high torque/low rpm so running a 55T rear sprocket we won't see a major loss in acceleration but the top speed may increase?

2. Power source range across the builds, most retail scoots use X3 12V SLA batteries, what set up is most common on the DIY DC motor scooters?

If nothing changes ill still be happy, as always the quest for more speed continues. If anyone is interested we have X2 goped bigfoot scooters that don't get used with their original petrol motors as the UK prohibits the use pretty much anywhere, we've gone for a 'bolt on' approach to cover them to electric, we've got the brakes and motor mounts sorted. Its a case of tidying everything up now and sorting the chain tension and sorting the gear ratios out...

Thanks in advance!

Tom

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fechter   100 GW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by fechter » Jan 22 2018 9:25am

Do you have any way to measure the battery current? That would tell you a lot. If geared too low, top speed will be slow, but it should be able to climb a tree and do wheelies.

Another test is to measure the full throttle speed with the wheel off the ground and compare that to actual riding.

It does seem like the gearing might be too low.
"One test is worth a thousand opinions"

hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 22 2018 10:37am

Hey fechter thanks for the reply!

The full throttle speed of the rear wheel off the floor did seem allot faster than on the road. However our excitement may have got the better of us on that one.

It didn’t exactly go very fast, nor did it wheelie or go barking up a tree ha.

We have a low budget Chinese 4 position throttle. Reads out 38v as we were testing low charge 18650 packs from my companions longboard project. Think they are 42v full charge. The voltage would drop like stink when on the gas. However didn’t let the resting voltage go below 36v.

If that info is of any use... I’ll get the actual stats from my friend that built the packs and get back to you.

In the mean time I have a Halfords volt120 kids scooter I bought for inspiration. That has x3 12v SLA batteries inside but I think they are very low A

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MrDude_1   100 kW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by MrDude_1 » Jan 22 2018 11:37am

10-12mph is about right.
Just like the "750w" goped ESR750.
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hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 22 2018 1:35pm

Spot on thanks mr dude.

I guess I just had really high hopes. Other similar vehicles using the 800w motor seem to be zipping along.

I did get those battery specs:
Sony VTC3
5s2p
Two of these so essentially 10s2p
36v around 20-30A continuous

Am I Wong in thinking these are high torque motors? I read they have a max RPM around 2500. So if I drop from 74T to 56T I won’t loose too much acceleration but may gain some top end?

hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 22 2018 1:36pm

That ESR750,

Was that a lithium ion battery and brushless motor?

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MrDude_1   100 kW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by MrDude_1 » Jan 22 2018 3:12pm

hicksi wrote:
Jan 22 2018 1:36pm
That ESR750,

Was that a lithium ion battery and brushless motor?
All of them run the same brushed DC motor.
You can get them in lead acid or lithium, but the difference is weight and range, not top speed or acceleration.
If you get an upgraded motor, you can accelerate faster or gear it to go faster... but if you try to push much more power than stock through the stock motor, it just burns up the brushes.

I already went through all that with my goped. I put 8S lithium in it to get a bit more speed and longer range... and it burned the brushes. It was so stinky the first time I took it to work (3 miles) on lipo that I had to put it outside.

I ended up redoing the whole thing with a 80-100 brushless motor, phaserunner controller and 16s lipo. It then went over 40mph with excellent range but the chain couldnt take the power and constantly needed replacement.
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hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 22 2018 6:11pm

Jesus. H Christ man.

That really made me chuckle!!!

I have many a stinky garage story involving various Chinese/jank electrical ‘good ideas’ we had. Don’t get me started on my buds spot welder. I have nightmares about that thing.

So moving forward i guess I’m not ‘missing a trick’. What I’ve got is what I’ve got. And our budget certainly doesn’t permit brushless just yet.

I think we’ll experiment with a few sprocket sizes. And our best hope is to acchieve greatness in the range dept. As speed is out of the question... The good news is we’ll have a tried and tested motor mount system by then that then new motors should be easy to bolt on...

Quick one, how can you tell when the brushes are gone? Does the motor just stop working?

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by ESR_RSE » Jan 22 2018 7:30pm

Looking at Mr_Dude's chart you seem to be geared for torque (You are like 75% the max speed of stock).

http://www.billetboard.com/showthread.p ... -questions

Perhaps swap to a different tooth drive gear?

Someone else in another thread mentioned on the older black cased stock ESR750 motor the following:
"My original ESR came with 13/76 (5.85 ratio) and a 53 link chain.
I switched to 15/72 (4.80 ratio) with a 52 link chain and I still have good take off speed and can top out at about 21 MPH."


I'm still reading up on upgrading batteries. I have an old used ESR shipping to me soon in WA.

hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 23 2018 3:39am

Hey mate that’s absolutely amazing. Thanks for digging that up.

Wish I got into the ESRs when they came out.

Goped industry fell flat on its arse years ago. Ended up with 3 goquads and two Bigfoot’s. Live near the beach so we wanted an electric version to ride along the fronts... we also didn’t want to start chopping up the bigfoot frame so we can switch back to gas if we ever wanted...

As the drive sprockets are generic China think I can pick these up pretty cheap. So I’ll try a 13T (stock 11T).

We’re currently looking to rip up new ‘old laptop’ batt packs to harvest the 18650s. We’ve got everything else we need to make them. We were looking at lipo packs but when you look big the prices jack up... guess we’re aiming for somthing like 10-20S within our limits

hicksi   100 µW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by hicksi » Jan 23 2018 6:16am

ESR-RSE

Just wanted to say that was a really helpful link.

Looking into either gearing up the front to 15T (%100)

Or gearing the rear down to 57T (95.5%) and saving a little acceleration

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MrDude_1   100 kW

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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by MrDude_1 » Jan 23 2018 12:21pm

LOL I forgot I even made that chart. :lol:
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Re: Torque / Speed Help - DIY 800W 36V Scooter build - 11F / 74R Sprockets - GoPed conversion

Post by ESR_RSE » Jan 23 2018 6:51pm

You might want to start with the 15 tooth on motor since I also read that under 12 it hurts the chain. Guessing due to very tight circle at higher speed and likely creates extra friction (perhaps even slower speeds)

There is a tensioner solution you should look into, "Slakinater" Chain Tensioner for ESR Electric Go-Peds. Order from DDM

Can you share further details on controller + batteries you swapped into the ESR? (i.e. where ordered or pics?)

I used to have a GoQuad, too bad not closer to WA or I would buy one off of you.

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