Drivetrain selection for an electric drive system

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robinhood   1 mW

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Drivetrain selection for an electric drive system

Post by robinhood » Feb 15 2019 4:41am

Hi all, I am designing an electric drivetrain for a three wheeler (tuk tuk) using a BLDC motor and controller. I am powering this with a lithium ion battery pack. I am currently using a chain drive with a single reduction gear to transmit power to the rear wheels. I would like to know the best transmission option for my scenario. I have considered using chain drive/ toothed belt drive / direct gear arrangement (sort of a single reduction gearbox) for this purpose.

It would be great if I can get some advice on the drivetrain selection with regards to efficiency, maintenance, ease of sourcing/manufacturing, costs etc. Thanks in advance!

Grantmac   100 W

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Re: Drivetrain selection for an electric drive system

Post by Grantmac » Feb 15 2019 12:51pm

If a single speed chain reduction can provide the gearing you require then that will be the simplest and most efficient.

Punx0r   10 GW

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Re: Drivetrain selection for an electric drive system

Post by Punx0r » Feb 16 2019 5:59am

As evidenced by its widespread use on bicycles and motorcycle. Anything you can do in your design to keep it clean and lubricated will increase efficiency, service life and reliability :)

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 16 2019 6:32am

Thank you for your replies.

I was considering shifting to a gearbox with a single reduction as it will require least care in terms of frequent maintenance. Also, isn't the efficiency of a gear system better than a chain drive? Please clear this point.

Thank you!

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Re: Drivetrain selection for an electric drive system

Post by afewskroosloose » Feb 16 2019 9:49am

In my opinion, chain drive is the way to go.

Its cheaper than a properly sized geared belt/HTD drive and the components are readily available if you need to replace sprockets and chain. I would try to design around standard shaft and bore sizes where possible so that you can easily replace components without custom boring or machining.

The efficiency of a properly designed chain drive is quite high and comparable to spur gear and belt drives (within a few per cent).

Engineering and fabricating a custom gear drive would likely be the most costly of the options and unless you really want to do it just for fun ( sometimes that's enough :D ), Id go with a chain drive.

The one caveat is that chain drives arent ideal at super high speeds without dedicated lube system. Find a horsepower rating table for roller chain (all over the web) and note the speed and power ratings and lubrication recommendations. In truth, roller chains are abused beyond their limits and maintenance largely ignored in many cases on go karts, dirt bikes, etc and they hold up very well. A reasonably cared for properly designed chain drive will last a very long time. Be sure you account for the ability to tension it properly by making your motor mount adjustable.

My two cents....happy building!

Voltron   1 MW

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Re: Drivetrain selection for an electric drive system

Post by Voltron » Feb 16 2019 11:06am

Chain drive is actually one of the most efficient gear reduction systems, in addition to being easily regeared if you want to change ratios down the line.

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 19 2019 2:01am

Thank you for your suggestions and views.
The efficiency of a properly designed chain drive is quite high and comparable to spur gear and belt drives (within a few per cent)
From my preliminary research, the belt drives seem to have heating issues and tend to wear out pretty quickly requiring frequent replacement, unless I go for kevlar reinforced belts which are quite expensive but still have heating issues. My application is to drive for ~8-10 hrs on a daily basis in conditions involving dust and frequent water logged roads (water and particle ingress is prevalent). This might require continuous maintenance for the chains but in case of a gearbox, it seems to be lesser.

Please let me know what you think.
The one caveat is that chain drives arent ideal at super high speeds without dedicated lube system
My application has a top speed of 55 km/hr that translates to ~650rpm. Will a chain drive handle this for a longer lifetime? (assuming I select the correct chain and tension it properly)
Chain drive is actually one of the most efficient gear reduction systems, in addition to being easily regeared if you want to change ratios down the line
Thank you for this view. But in case I have a single gear spur arrangement, how difficult will it be to change ratios later?
Last edited by robinhood on Feb 20 2019 12:36am, edited 1 time in total.

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 19 2019 2:02am

Punx0r wrote:
Feb 16 2019 5:59am
As evidenced by its widespread use on bicycles and motorcycle. Anything you can do in your design to keep it clean and lubricated will increase efficiency, service life and reliability :)
Sure, will keep this in mind if I continue to use a chain drive!

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Chalo   100 GW

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Re: Drivetrain selection for an electric drive system

Post by Chalo » Feb 19 2019 2:26am

robinhood wrote:
Feb 19 2019 2:01am
But in case I have a single gear spur arrangement, how difficult will it be to change ratios later?
The distance between gear centers will vary with ratio, and it's difficult or impossible to change without remanufacturing parts. Chains are easy. They're tolerant of imprecision and wear, and they remain more efficient than gears until they are quite worn out. Replacement sprockets and chain are inexpensive. You can use a chain case to reduce maintenance and keep things cleaner.

Have you ruled out the use of a front hub motor for your trike? That might be the simplest, quietest, and lowest maintenance option.
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Re: Drivetrain selection for an electric drive system

Post by amberwolf » Feb 19 2019 11:07pm

robinhood wrote:
Feb 19 2019 2:01am
My application is to drive for ~8-10 hrs on a daily basis in conditions involving dust and frequent water logged roads (water and particle ingress is prevalent).
That's probably going to be a HUGE battery pack.

Or a small one that can be charged at a very high rate so you aren't sitting idle charging most of the day. LTO might work.

Or several smaller swappable ones, and a central charging station they're kept at that you regularly visit to swap out.

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Chalo   100 GW

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Re: Drivetrain selection for an electric drive system

Post by Chalo » Feb 19 2019 11:21pm

amberwolf wrote:
Feb 19 2019 11:07pm
robinhood wrote:
Feb 19 2019 2:01am
My application is to drive for ~8-10 hrs on a daily basis in conditions involving dust and frequent water logged roads (water and particle ingress is prevalent).
That's probably going to be a HUGE battery pack.
Yeah, no kidding-- I missed that detail. There's no way an electric tuktuk with that kind of endurance will be as economical as a normal gas powered version. What's the goal here? Demonstration of the possibilities, or something practical?
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 20 2019 12:25am

Chalo wrote:
Feb 19 2019 2:26am
robinhood wrote:
Feb 19 2019 2:01am
But in case I have a single gear spur arrangement, how difficult will it be to change ratios later?
Have you ruled out the use of a front hub motor for your trike? That might be the simplest, quietest, and lowest maintenance option.
A front hub motor is an option, however for my application, I would need >5kW hub motor which is turning out to be expensive, also due to the fact that the trike is being steered by the front wheel, I'm afraid it might affect the vehicle dynamics in terms of steering, a lot.

Could you give me some links to resources about chain tensioning and other chain drive design/maintenance parameters? It would be great to read about them!

Thanks in advance!
Last edited by robinhood on Feb 20 2019 12:34am, edited 1 time in total.

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 20 2019 12:26am

amberwolf wrote:
Feb 19 2019 11:07pm
robinhood wrote:
Feb 19 2019 2:01am
My application is to drive for ~8-10 hrs on a daily basis in conditions involving dust and frequent water logged roads (water and particle ingress is prevalent).
That's probably going to be a HUGE battery pack.

Or a small one that can be charged at a very high rate so you aren't sitting idle charging most of the day. LTO might work.

Or several smaller swappable ones, and a central charging station they're kept at that you regularly visit to swap out.
Not really huge, I'm powering it with Li-ion packs that weigh around 30kgs, chargeable in ~6-8hrs. Thanks for the other suggestions, I will take note!

robinhood   1 mW

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Re: Drivetrain selection for an electric drive system

Post by robinhood » Feb 20 2019 12:31am

Chalo wrote:
Feb 19 2019 11:21pm
amberwolf wrote:
Feb 19 2019 11:07pm
robinhood wrote:
Feb 19 2019 2:01am
My application is to drive for ~8-10 hrs on a daily basis in conditions involving dust and frequent water logged roads (water and particle ingress is prevalent).
That's probably going to be a HUGE battery pack.
Yeah, no kidding-- I missed that detail. There's no way an electric tuktuk with that kind of endurance will be as economical as a normal gas powered version. What's the goal here? Demonstration of the possibilities, or something practical?
When I mentioned 8-10 hrs, I meant to say the entire operational time in a day. The distance covered wouldn't exceed 125 miles a day which seems to be normal. I'm still working out the economics, but just figuring out the possibilities as for now. Trying out different motors and drive-train arrangements. Most of the suggestions here have favored the use of a chain drive which I am already using. Will try playing around with the gearing to obtain optimum performance characteristics!

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