Go-karts are a huge amount of fun, but often lack the most basic of mechanical conveniences such as a reverse gear. You can’t start a small four-stroke engine in reverse, so their simple chain drive transmissions lack the extra cogs to make it happen. Enter [HowToLou], who has given his go-kart a reversing option by the addition of an electric motor.
It’s an extremely simple arrangement, the motor is a geared 12 V item which drives a V-belt to the axle. The motor is mounted on a pivot with a lever, such that normally the belt isn’t engaged, thus reverse can be selected by pulling the lever. A simple button switch applies power to the motor, meaning that the machine can travel sedately backwards on electric power.
We’re not entirely convinced by the integrity of some of his fixings and it would be interesting to see how much the V-belt wears under the influence of the pulley when not engaged, but as an alternative to a full gearbox we can see the point. But then again as regular readers may know, we’re more used to full electric traction.
So, presumably you need to carry a battery too, now.
What’s next? electric start? Yeesh. Fuggedaboutit. Leave the tonnage at home.
A simple reversing gear would certainly be cheaper and lighter
This often done in cars with motorcycle engine swaps.
It’s done in some hybrid vehicles too, reverse being done by the electric motor.
Basically all eCVT based vehicles are like this. They are a very basic design where it’s all just a planetary gearset moving power around between the engine, the two electric motors, and the wheels. Much like the Go-Kart example here, there’s no mechanisms or allowances for the output of the engine to be reversed. So they simply move the car on electric power alone in reverse. And with the way the eCVT is set up, the engine can still generate power via MG1 (the starter/motor gen) while doing this to keep MG2 powered and essentially runs as a series hybrid in that state.
The other hybrid/PHEV design that I’m aware of other than the eCVT is the old Honda IMA-like design where they keep a traditional automatic transmission and replace the torque converter with a single electric motor and a couple clutches. These will have the traditional reverse mechanisms as part of the automatic transmission. Ford uses this on their Explorer and F-150 hybrids and I think Kia/Hyundai use it in some of theirs.
Pretty sure the original Insight (the two door lozenge of a car, supremely cool, IMA) was a manual transmission. You could defeat the engine stop/start by holding the clutch in, I think. It was a long time ago. Also using recirculate on the A/C would do it.
I do remember the Insight piston-to-cylinder head clearance was so tight you had to read a letter code off of the top of each plug and replace them with the same code. The letter told you the indexing relative to where the threads would bottom out. Otherwise the piston could collide with the side electrode.
Best of all, the battery pack was just a heap of rechargeable D cells!
One other way to reverse – use a 2-stroke engine like very old Saabs and a bi-directional starter motor. Shut down, start in reverse, shut down, go forward. Two stroke engines can run backwards.
I’m just being a pedantic jerk, as most nerds are prone to. Ignore me. I rather like my Prius eCVT, especially at current gas prices.
Anybody remember the Litestar? Did it even have reverse? I want one. :-)
I’m in the decision mode for the same dilemma, right now. This solution works, but slowly, and not the most elegant solution, as there is an off the shelf forward/reverse kit that will fit his kart. It uses a planetary gear that shifts with a cable from driving the shaft, to driving the outside body that has a sprocket attached. Unfortunately, it’s not going to fit the shaft on mine, so I’m faced with building it from scratch, or machining my shaft down to size and re-splining it. There is also a more expensive forward/neutral/reverse gearbox to be had, but again, doesn’t fit my application.
Also, this electric solution has nothing to prevent someone accidentally stomping the accelerator while the reverse is engaged. A linkage to a locking pin on the pedal would do. Can’t pull the reverse lever unless pedal is at rest, can’t depress the pedal unless reverse lever is at rest. A starter clutch from a small motorcycle would also be a nice feature. That would negate the need for the tensioning pulley and lever altogether. The motor would never be engaged with the drive train unless powered, and could use a simple foot switch that, if far enough from the accelerator pedal, means you couldn’t have your foot on both anyway.
Maybe instead use the same concept as the Prius does, have a differential that both electric and engine are driving.
as a child i had a pedal car that used a friction handbrake against the wheel. it was a simple system that worked well. this could use a pair of pulleys coupled to the crankshaft to give a fixed low speed then pull a lever to couple the driven pulleys rotation to a wheel via friction. make sure to keep belt guards over the pulleys though to avoid getting hair and fingers tangled.
How about just a simple centrifugal clutch on your 12VDC reversing motor, a longer chain and an engine mounted adapter plate to add the motor and an idler gear to the existing chain drive? Might have to play with the clutch engagement speed but should work
Why not chain drive instead of a belt? Think for a minute about the Cassette (the cluster of gears on the rear wheel of a multi-speed bicycle) on a bicycle. When you pedal forward the cassette rotates the rear wheel. When you pedal backwards the cassette ratchets and the wheel does not turn backwards. So, for the reverse motor you mount the cassette backwards so that the electric motor turns the axle shaft backwards thus giving you a reverse gear (or gears if you incorporate a derailer so you can shift between the gears on the cassette). When the go-kart is in forward motion the cassette for the reverse is ratcheting.
Hello AB, I am faced with a no reverse problem on a Triumph Spitfire that I put a motorcycle engine in. I am not rich and everything is on a budget because, well, I am cheap! I thought about doing the very thing you explained, but when I thought more about it, at least in my head, it won’t work and here us why. The cassette only ratchets one direction and whether placed on the drive side or drivin side, it would only lock going forward, then when the car/cart overcame the speed of the cassette, would it ratchet. In other words, if the electric motor was turned on and the chain drive the car/cart backwards, it would only ratchet if the car/cart went faster than the driving motor. Now, turn off the electric motor and use the engine to propel the vehicle, the cassette is pushed to force the motor the wrong direction.
The same principle is used in an electric start motorcycle that doesn’t use a bendix. When the starter us engaged, it spins a one way clutch. Once the engine starts, the speed “overruns” the speed if the ine way clutch… it is all in the same direction.
If you can prove me wrong on this, I would love it, because I lay awake at night trying to figure out a low cost reverse option.
I thought about using a flex plate on the driveshaft and a bendix starter, that is only engaged when active and retracts when not, but I simply don’t have room near the rear of the car and frankly don’t want a saw blade spinning next to my legs!
Please chime in, I would live to hear a rebuttal, or other ideas!
Brad
This is interesting. I wonder if I can implement something similar for my trike. I only have forward gears and have to push it backwards.
The permanently engaged Vee belt will probably be fine for a long time. The Myford TriLeva lathe ( http://www.lathes.co.uk/myfordtrileva/ ) used a very similar arrangement and was intended for light-industrial use.
My 96 Honda Goldwing accomplishes reverse similarly. Pop it in Neutral, pull a lever to slide over an engagement, boom. Your starter motor is reverse.
With the GL1800’s you don’t even need a lever. Just put it in N and press the reverse button. it still uses the starter though.
Neat, hope it was done with just what was on hand, in that case, cool. but if thought out and parts acquired, eh, not so great. If you going to think it through, then perhaps actual reverse gear select with the lever??
I would think it would be easier to run a cog direct onto the drive chain with a lever. Much simpler. I’ve only ever seen it done this way. With both systems you still need something to remind you it’s engaged!!!
Otherwise be always easier to use a quad motor with reverse built in…
Old tillers have a wheel with rubber on it that you would move lever to push the wheel into the drive belt on out side of the belt spinning the wheel that went to gear box backwards thus moving it backwards when gear box in neutral big rear tine tillers had this before the actual gear box would have rear tine running in reverse option which was the cats meow
There are Forward – Neytral – Reverse gearboxes avaialble for gokarts for about $100 that remove all this complexity. https://amzn.to/3DgJOn3