Electric Cyclekart - similar to the Morgan 3 wheeler thread but 4 wheeled

[Madmarcus]

Similar to the electric Morgan thread from a couple of months ago I'm looking to build a cyclekart. Think vintage Gran Prix go kart with 17" motorcycle wheels to give the old school pre-WWII look. Driving on grass and dirt with an initial design goal of 600rpm / approximately 40mph depending on specific tires.

Constraints
48v system (firm)
3kW (conservatively) 5kW (firm maximum)
500 lbs max weight but I'm aiming for 400 lbs (both weights include the driver)

I could buy (new or used) a single bigger motor as was suggested in the Morgan thread but the my experience with smaller silly vehicles suggests using two e-scooter motors in the 48v 1500-2000W range each driving one rear wheel on stub axles. That's the heavier solution but keeping each side as lower power might provide some saving in cost.

What is the current consensus on random e-scooter motors? Any brands to focus on or avoid? Any particularly low kV motors to help keep the rear sprocket size down? I am somewhat price limited by the competition rules so I'm probably not looking for high end motors.

Could a 6374 or similar smaller eskateboard motors work? My thought is that they would overheat almost instantly since they are at most 1/4 the mass of the MY1020 shaped escooter motors but I have no experience with them? I can probably get reasonable airflow over them but nothing more than you would get on a skateboard or bike mounting.

Links to motors are purely for example purposes! I didn't take any time other than to quickly find examples to compare mass.

 

[Madmarcus]

Whether it's the wrong part of the forum or people didn't think I provided enough info I'll ask followup questions in the escooter part of the forum.

 

[fechter]

A small eskateboard motor is probably going to overheat pretty badly. That's a lot of weight.
Even with a large size 3kw motor, that much weight is going to be a heavy load, especially if you run into any kind of hill. A physically larger motor will take longer to overheat. You may need more than one gear. Something more like a Sur-ron motor would be in the ballpark.

 

[Madmarcus]

Ok, perhaps I'll continue here for now.

The current solution is to use 2 48v 2kW MY1020s. Build guidelines say I can't go over 48v and all of the 2.5kW rated motors I'm finding are either 60v or 72v. Since weight matters I'm not sure that the heavier 60v motor would be enough better when run at 48v to be significant but that is one of my real questions. Even with two of them I'm not matching the 12.4 Nm that the Honda GX200 (the normal motor on these cyclekarts) can put out but that is just looking at specs not motor curves.

The esk8 motors are still tempting when I see go kart builds although the build guidelines maximum of 5kW rated power kills them as anything interesting is rated at more than 2.5kW anyway. Same with the Surron motor which I'm fairly sure is rated well above 5kW.

 

[classicalgas]

The cycle kart rules seem to be deliberately handicapping both electric drives and three wheelers like the Morgan.

Your effective track is about half what the four wheel cyclekarts have, and many of those are as low as is practical already, so you'll have a cornering disadvantage.

The theoretical electric drive advantage is mostly negated by the torque converter most of the karts run. That's on top of the power limit that's already handicapping electric karts vs ICE.

 

[Madmarcus]

The cycle kart rules seem to be deliberately handicapping both electric drives and three wheelers like the Morgan.

The theoretical electric drive advantage is mostly negated by the torque converter most of the karts run. That's on top of the power limit that's already handicapping electric karts vs ICE.

True.

To be fair it started with a bunch of people who liked tinkering with motors. I get the feeling that the electric rules were as simple as looking at the 5kW rating on the GX200 and and saying 5kW is 5kW. Of course even if I recognize that I don't think I'm qualified to really lobby for a different set of rules. So I'll try to build one that is at least marginally comparable because I think it's a fun challenge while I try to get other people interested in reworking the electric rules.

Lack of knowledge of electric drive trains doesn't quite explain the 3 wheeler issue but there seem to be some inherent conflicts in cyclekarts. Is it about making things that are cool or is it really racing? And if it is racing shouldn't everyone start from the same baseline? Weird in a way since the pre-WWI cars were at times such a mish mash of different design ideas.

 

[classicalgas]

there seem to be some inherent conflicts in cyclekarts. Is it about making things that are cool or is it really racing? And if it is racing shouldn't everyone start from the same baseline? Weird in a way since the pre-WWI cars were at times such a mish mash of different design ideas

I'd agree, there's the usual conflict between "build a fun car in your home shop on shoestring"( which isn't far from the original street driven cycle car DNA) and "I want to win"( which is where a lot of the cycle car racing specials came from) The conflict between those two driving viewpoints has been the downfall of so many "race for fun" organizations (from vintage auto racing to soapbox derby ) that it's become an accepted fact that rulebooks will look like an unabridged Websters within a decade of the formation any new racing series.

The maximum track spec is there for four wheelers, I think, to encourage passing on narrow race courses. You know that if there weren't a limit in the rules, you'd see track widths grow to absurd dimensions. Three wheelers suffer as a result, at least on paved courses.

What the cyclekart thing started as was sort of a loose "spec racing" series, where the chassis and drive train of all the cars was supposed to be comparable, with just the body open to individual interpretation. That didn't last long.

I think a three wheeler with AWD would be fun, especially on the dirt tracks. Could you learn to balance wheelspin if you had two throttles? (one for the front pair of motors and one for the rear ) Accelerate with both axles, let the front pair drag the car around the corners, and step the rear out at will.

 

[Madmarcus]

I'd agree, there's the usual conflict between "build a fun car in your home shop on shoestring"( which isn't far from the original street driven cycle car DNA) and "I want to win"( which is where a lot of the cycle car racing specials came from) The conflict between those two driving viewpoints has been the downfall of so many "race for fun" organizations (from vintage auto racing to soapbox derby ) that it's become an accepted fact that rulebooks will look like an unabridged Websters within a decade of the formation any new racing series.

Unlike some other race for fun groups there is still a portion of the hobby that pays at least lip service to "we're here to have fun not compete" but it's clear that most of it has gone the way you describe.

Luckily, in a sense, I'm more interested in designing this as an exercise at working within the constraints.

 

[classicalgas]

Luckily, in a sense, I'm more interested in designing this as an exercise at working within the constraints.

I looked at doing a three wheel Morganesque cyclekart, but decided that building for street use made more sense for me ( even though I could fit a small dirt track on my property ) So building to meet "road legal" specs instead of cyclekart specs.

Pedals and a nominal 750W, 30mph top speed. Light as possible with 1920's style aero and body construction, yard tool battery packs for ruggedness and hot swap battery capability.

There's an authentic four wheel Morgan three wheeler special out there, with tube videos of it racing...it's a hoot!

 

[Madmarcus]

I looked at doing a three wheel Morganesque cyclekart, ...it's a hoot!

I've watched it! Who knows I might even hit you up for info about getting something street legal in the same homebuilt class 3 ebike fashion.

Your video is one of the reasons I'm going to keep working on this even though it is fairly clear that I'm at least going to have to violate the guideline about battery size. For now I'll probably stay with 48v as I don't feel much of a need to compete with the 80+mph electric cyclekart on youtube.

 

[classicalgas]

I've watched it! Who knows I might even hit you up for info about getting something street legal in the same homebuilt class 3 ebike fashion.

Basically I'm putting a TSDZ2B in a used tadpole trike ( that came with a 3spd IGH ) and driving that with EGO yard tool packs.
Bodywork is laminated 3mm plywood, including a full belly pan.

I'll fiddle with gearing until I can't pedal fast enough at 30mph to keep the power boosted.

 

[MxusMick]

I have a salvage treadmill motor mounted to a trike with a belt to pulley on one rear wheel, it has an on off button throttle. With a 36v battery it goes about 20mph, very sketchy, but silent and belt works good, no drag pedalling. It's a cheap way to get powered up, if you like scrounging.