Gearbox from monster truck.

[Bluefang]

Anyone ever use a HPI racing moster truck gear box, they come in both 2 and 3 speed ones from what i can see, from the supplier the new 3speed ones are like $130 complete, $90 in kit. These trucks run on a 2.9hp engine, do you guys think that the gearbox would handle 2-3kw? or even anything close.
link
http://www.hpiracing.com/products/en/87218/

 

[Hillhater]

Nice piece of kit and it can likely handle 2-3kW , but i doubt it would handle the torque at the low rpms that i am guessing you would need from it on an Ebike

 

[Bluefang]

hmm, but connecting the motor directly to the box and having the gear down after, it might be able to handle the torque at 10,000rpm, plus it has a slipper clutch inbuilt from reading about it. Just something interesting i thought i would throw out there

 

[LI-ghtcycle]

Very interesting! One thing for sure, it is compact!

 

[recumpence]

You might want to look at transmissions for 1/5 scale RC cars. I bet there are a few that would work well for our application.

Matt

 

[Byte]

I've been in RC cars for a few years, 1/8 to 1/18 scale. I've converted a Losi LST (which got one of the best 1/8 drivetrains, if not the best. Atleast it's FAR better than a Savage imo) to brushless, using a Plettenberg Bigmaxximum (motor), Quark 125A (ESC) and 5S Flightmax (Almost the same as Turnigy) LiPo. I've pulled 3+ KW (Yes, this thing does standing backflips lol) through the transmission without any problems. The transmission is cheap if bought on eBay and it's a 2-speed. http://cgi.ebay.com/Losi-LST-XXL-UP...Accessories&hash=item4cf4449c73#ht_3451wt_905

IF you want to use a RC car transmission, than use this one and not one from a Savage IMHO.

- Patrick

 

[Bluefang]

see i knew i posted here for a reason, thanks for the info Byte
wow for only $35AU i can get a 2speed automatic transmission capable of 3+ kw??? ROFL

Now your saying this is from a 1/8 car, and Matts talking about 1/5 cars, hmm wonder if they can handle 6kw thru them. I ll have too look around and see if this brand makes 1/5 sized versions.

Derek

 

[vanilla ice]

There'd be another ~5x reduction between the truck box and the tire right..

 

[Byte]

see i knew i posted here for a reason, thanks for the info Byte
wow for only $35AU i can get a 2speed automatic transmission capable of 3+ kw??? ROFL

Now your saying this is from a 1/8 car, and Matts talking about 1/5 cars, hmm wonder if they can handle 6kw thru them. I ll have too look around and see if this brand makes 1/5 sized versions.

Derek

Yes, parts for this truck are very cheap. And jup, I put 3KW through it.

FYI: This gearbox has a external and internal 2-speed. My English is not very good, so I'll try to explain it with an image, this is the gearbox opened up:

External: You can't use this one as it will shift at about 25.000rpm or so. (It's possible to adjust it, but I don't think it will be useable)
Internal: You can use this one, it can be shifted by hand or you could hook up a servo on the otherside.
Reverse: You won't need this I assume.


IIRC not many 1/5 or 1/6 cars use a gearbox. You could search for these cars, although I'm 90% sure they don't use a gearbox:
- HPI Baja
- One of the FG cars (http://www.fg-modellsport-gmbh.de/)
Oh, Losi doesn't make a 1/5 or 1/6 scale car.

EDIT: I bought my LST used, it's probably around 3-4 years old and my gearbox still looks like NEW, it's very tough.
EDIT2: I haven't got the datalogging anymore, or else I could show you the 3KW peaks...

 

[1000w]

Like mentioned earlier, no mater where in the drive line, I can see these gear boxes having problems moving an ebike and rider when they are designed to move a much lighter RC car.
I would love to be proved wrong however, this is what this hobby is all about, new ideas and testing.
Good luck.
Matt.P.

 

[vanilla ice]

How much does one of those trucks weigh? How much are we talking $$ for the 3kW gearbox you use?

 

[Bluefang]

The automatic 2 speed gears, i guess thats how the motor is connected to the gearbox normally, 2 gears on the output shaft from the motor connects to both of those gears on your gearbox? Been a slipper spur gear setup they start off in the lower gear and once rpms go over a set amount they switch to the higher which locks in until the rpms drop? From what i gather it shouldn't be too hard to run the Turnigy 200kv 63-74 motor at 100V to get 20,000rpm pretty sure its been done before and the figuring out how to adjust to 20,000rpm shift should be easier, the low amps will keep the torque down and save the controller in the process I would prefer to run this way as that section includes a slipper clutch, hopefully keep the box alive longer

So is this box a 4speed box? and do you know the ratios of all the gears? Reverse is always useful at some stage
To run all 4 gears i guess i need
http://cgi.ebay.com/Losi-LST-XXL-Slipper-SPUR-GEAR-Transmission-LST2-/220719957891?pt=Radio_Control_Parts_Accessories&hash=item3363ef4783
http://cgi.ebay.com/Losi-LST-XXL-MACH-454-CLUTCH-BELL-Gears-LST2-427-/220733640689?pt=Radio_Control_Parts_Accessories&hash=item3364c00ff1

 

[Thud]

What pitch are these gears? 48? 16?
I think a quick look through Machinest's handbook will let you figure the life expectancy of these gears.
I only have my 10th scale stuff gathering dust on the shelf. A shock reducion system will proly be required. (slipper clutch at min)

EDIT: that rc stuff is all 48 pitch.....& designed for much lighter shock loadings....add they allways have a slip built into the driveline some where...a ball diff. or a slipper clutch. The input & output shafts are also tiny. Lots of primary design issues to solve to make it workable.

Scale it up by 180% & you will be right in the ball park of an e-bikes needs.

 

[Bluefang]

All good its only research atm, no money to buy anything lol.

Pretty sure they have a slipper clutch system on the 2 automatic gears leading into the main body, but then i know nothing about gearboxes really, relying on the experts. For shock dampening would running a V-belt to the rear wheel rather then chain, would that be adequate or do i need a proper slipper clutch. Seems gas bicycles use this to good effect with high powered engines and 3speed internal hubs.

 

[fechter]

The principle used in the two speed external gear setup is interesting.
What if you used a pair of belts instead of gears on something built a little stronger?

 

[Wheazel]

Will maybe work with a high rpm, low torque motor, and additional reduction after the gearbox.
I am pretty sure that anything else would kill it instantly or reduce the life significantly.
The small parts cant handle big forces.

 

[Byte]

How much does one of those trucks weigh? How much are we talking $$ for the 3kW gearbox you use?

My truck weighs exactly 7KG (15.5lbs).

The automatic 2 speed gears, i guess thats how the motor is connected to the gearbox normally, 2 gears on the output shaft from the motor connects to both of those gears on your gearbox? Been a slipper spur gear setup they start off in the lower gear and once rpms go over a set amount they switch to the higher which locks in until the rpms drop? From what i gather it shouldn't be too hard to run the Turnigy 200kv 63-74 motor at 100V to get 20,000rpm pretty sure its been done before and the figuring out how to adjust to 20,000rpm shift should be easier, the low amps will keep the torque down and save the controller in the process I would prefer to run this way as that section includes a slipper clutch, hopefully keep the box alive longer

So is this box a 4speed box? and do you know the ratios of all the gears? Reverse is always useful at some stage
To run all 4 gears i guess i need
http://cgi.ebay.com/Losi-LST-XXL-Slipper-SPUR-GEAR-Transmission-LST2-/220719957891?pt=Radio_Control_Parts_Accessories&hash=item3363ef4783
http://cgi.ebay.com/Losi-LST-XXL-MACH-454-CLUTCH-BELL-Gears-LST2-427-/220733640689?pt=Radio_Control_Parts_Accessories&hash=item3364c00ff1

Yes, the automatic 2-speed is connected to the motor directly. Yes, they start of in the lower gear and at X rpm they switch. If you don't want to use the external 2-speed but you need the slipper clutch you can lock it in first gear if you want. (Many converted LST's to brushless use this as they don't necessary need the 2-speed)

Yup, it's a 4-speed.
Internal 1st gear ratio: 4:1
Internal 2nd gear ratio: 2.09:1
External: Depends on the gears you use ofcourse.

You would indeed need those part, although I think it's hard to set these pinions on a motor shaft, you might want to look at some custom pinions/spurs with a Xmm bore.

Will maybe work with a high rpm, low torque motor, and additional reduction after the gearbox.
I am pretty sure that anything else would kill it instantly or reduce the life significantly.
The small parts cant handle big forces.

You probably are right on this, as this transmission only needs to move 7 kilogram instead of 100kg.


I've seen crazy things on forums, like an LST2 pulling a 1:1 car a few meters. This one is very interesting too, it's a guy who had a Savage (The one you told about before.) and converted it to brushless. Ofcourse he didn't use the gearbox and modified A LOT on the car. Anyway, he's running a big fat Lehner 2280, 14S LiPo (Yes, that's more than we run in our bikes) and a Jeti ESC. Ofcourse he's stripping gears, but just take a look at this datalog:

9+ KW!

 

[Bluefang]

Wow with the internal gears been a 4-1 and then a 2-1 it certainly makes it easier not using the first pair of automatic gears. Talking about shock loading, running this gearbox straight into a clutched 5-1 reduction drive from a pocket bike might be the easiest way to soften the start up, its a sequential gearbox isnt it, same as a motorbikes so the actual gear changes if done fast wont have much of a shock effect on the gearbox. Olaf-Lampe used a pocket bike gearbox with a massive turnigy to save the controller and you could hear the clutch slowly gripping the bell to apply force, wonder if it can save these small gearboxes.

Byte are you able to post any pictures of the way your gearbox and motor are connected? Whats the diameter of the input shaft for the gearbox, can a simple nylon "spider"joint(no idea if thats what there actually called) could be used to allow some flex.

Love the youtube videos of what these 1/8 model trucks can do, particularly the ones where they tow people in a trolley behind the car. I am not really thinking of using this on a bicycle, more like one of those old 100cc scooters so even heavier . I have seen a 60kg tank replica using similar gears pull a 4wd car, so at worst it will be a interesting test

 

[Metallover]

My thoughts are that RC gearboxes won't work. They could be scaled up, but they were designed for high (40-50k) rpm inrunner motors in a vehicle around 10-15 pounds.