gru units
 

i have fitted a hpi gru to my cc-01 and after the modifications to get it to fit i am trying to find out about the ratio's of the different gru's

i am running a tekin rs with 21.5 brushless motor and on its own is way too fast so after a search about i came across a hpi gru so off we go

my biggest problem was getting the gears to mesh as i am using the alloy motor mount and metal spur gear with the bigger of the 2 pinions that come with it as the smaller one was too slow

in the end i had to modify the chassis and also had to drill a new hole in the gru unit to get the mesh nearly right

would it have been easier to go for 1 of the rc4wd gru's and if so how would i know which to go for

thanks for any help i can get on this

regards ian

I'm going to try to answer what I think your question is. (Capitals, spaces & punctuation are good things, friend)


The RC4WD GRUs are the bomb! With the 21.5 system you're using, the 4:1 version would probably be best. I've heard they don't like being spun too fast for long periods, but if you take proper care, it should last.

Re: gru units
 

I do appologise for my punctuation but to my defense i had not been up long :oops:

I thank you for your reply my friend and will take on board what you have said and maybe look for an rc4wd gru.

The truck is built for scale use so will not be run at full speed for prolonged periods.

Thanks again ian

Cheers! Check the classified section. I got mine through there.

Re: gru units
 

Yes, the RC4WD gru is much easier to use in the cc-01. Minimal adjustments to the chassis tub (gru is same diameter as motor and pushes motor back into battery compartment (same as the HPI gru) but no other mods necessary.
the RC4WD ratios are 2:1, 3:1 and 4:1 (each available separately). The HPI is something like 7.2:1 or thereabouts. I would recommend changing the motor too to a 55t.

[edit: I have cc-01 rigs with each RC4WD 4:1 gru and HPI gru. I'd personally never use the HPI again. The quality of the RC4WD unit is so far superior its worth the extra $20 to buy theirs over the HPI unit. At least last time I bought them that was the difference, $20 vs $40.]

Re: gru units
 

Thanks again for even more good information that has got me sorted now rc4wd it will be. "thumbsup"

What gru would you use with the 55t motor ??

I would like to keep the motor i have in there now (tekin 21.5 brushless)as i love how smooth it is and prefer brushless to brushed.

It also has plenty of settings i can mess around with (drag brake,push etc etc).

Thanks again guys :)

Re: gru units
 

I use a 45t with a 2:1 and its a great combo of wheel speed and low speed torque. With your 21.5 I would go the 3:1 to keep it still a bit fast ot 4:1 to slow it right down and give great torque.

Re: gru units
 

Ok thanks again.

Is it possible to just change the gears rather than buying the 2 units (3.1/4.1).

As that way i could buy the 3.1 and also a spare gearset.

regards ian

Re: gru units
 

Not that I know of, but they are so cheap you really could afford to get both.

Re: gru units
 

With 55t I run 4:1. I like it slow. Ill post a video shortly showing the max speed with that setup.

Re: gru units
 

I have the Great Planes GD-600 GRU. The ratio is 2.5:1. I got it for $5 shipped from ebay. It is a fairly good unit but you will need to turn down the pinion shaft on the unit to fit the stock Tamiya pinion gear. I did so by mounting the stock motor in the unit then ran it against a steel file until I got it down to the right diameter.

I believe there are two other pinion sizes available for the GD-600 which are sold separately.

Re: gru units
 

Maybe if i was in the us i would be being in the uk not so cheap.

Price of gru's x 2 plus postage plus possible import and royal mail handling charge not so cheap :x

Thanks again folks

Re: gru units
 

Here is the video.
MDR 5 7 09 - YouTube

It's about 5 minutes long but the pertinent part is the last 9 seconds where the rig does a 'fly by'. Rig has 55t motor and 4:1 rc4wd gru. Tha is a full throttle pass.

Re: gru units
 

Now that is impressive i likes that a lot.

Looks like time to spend some money lol.

i was also looking at your steering is this hard to do and do you know any links how to do this.

One last question what combination esc/motor are you running as its a minefield working out whats good bad or useless.

thanks again

regards ian

Re: gru units
 

Thanks Ian.
The steering isnt very hard to set up. I find its an improvement but if you have a brand new cc-01 the steering will be tight and it may not be necessary to do this. I did the steering as an experiment and was happy with it. You should drive your cc-01 as stock first to get a sense of the steering slop and then make adjustments, as with any change, so you can see the direct effects of modifications.

I'm not very picky about the esc's or motors really. I used to be and my favorite was the Castle Creations Sidewinder. I have that in a couple rigs. However, I also have the stock cc-01 esc in a couple rigs (one not a cc-01, lol). There are two main differences I see in them, first is the CC Sidewinder (or other top shelf brands) are programmable so you can adjust the drag brake and other things. The drag brake isnt as important if you're running a gru because the gru acts as a drag brake (although not adjustable).

Secondly the better esc's don't have a delay when going from forward to reverse. This can mean the difference between rolling your rig down an embankment or saving it, lol. There was one I used to run that was HORRIBLE about that. The delay was too long and was frustrating to drive. Pulled it after one drive. I can't remember the name now, started with an L maybe...
For me, the quality of the esc isnt important but if I were doing competitions I would be more inclined to use better equipment.

For motors I like Novak's Fifty-Five (55t motor) but also run the basic Integy 55t motors. Again, I don't see much difference although I like the Novak's reputation for quality.

Re: gru units
 

Lots of good info here, I have a question though, I just picked up a used RC4wd gru and I don't know which one it is, is there any way to tell which one it us and what pinion does it take?

Re: gru units
 

OOh, wish I could help. I've only ever had the 4:1 so dont know the differences. I would suggest emailing or calling RC4WD directly on that. They're very helpful.

Could you count the teeth on the gears and divide the big one by the small one? EG: big gear 48t, small gear 12t would be 4:1.

I just insalled a hpi gru in my lr3 and it works great but wow it's noisy. Do they all make noise?

Sent from my DROID3 using Tapatalk 2

Re: gru units
 

I packed mine with grease and it is still noisy. Shouldn't be any grinding noises or anything, but it's full of metal gears so yes, it makes some noise.