1/6 Losi Hummer (CC1717) Build
 

1/6 Losi Hummer (CC1717) Build

With Castle selling their 1717’s for a bargain recently, I decided to plan a build that would make the most of one of these motors:


http://i779.photobucket.com/albums/y..._4818Small.jpg

Since the 1717 is almost as large (20oz) as my Neu 1527 (21.8oz), I figured I could plan another larger-scale build in the 16-20lb range. I again will make use of the Losi LST2/Muggy platform because I have seen that it is quite capable in a truck this size. If you haven’t seen it, here’s my previous large-scale build:

http://www.rc-monster.com/forum/showthread.php?t=26979

The first thing I had to consider with the 1717 is that it has a relatively high kv and a larger diameter than the 15-series. For both of these reasons, I looked for a center diff with a larger spur gear and decided on the AE RC8T that comes with a 54t spur. I want to have gearing options for 6s-8s and for both MT and 1/5 scale tires. Playing with the top-speed estimator, I was happy with the gearing options available with the 54t spur. For example, with 1/5 scale tires and running on 8s, I could use a 12t pinion and get a top speed around 51mph (I’ll be running 45/11 Muggy diffs):

Differential Ratio: 4.090909090909091
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 12
Total Voltage: 29.60
Motor KV: 1580
Tire Diameter (inches): 6.8
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 4.5 : 1
Total Ratio: 18.40909 : 1
Tire Circumference (inches): 21.36 inches (542.62 mm)
Rollout: 1.16:1
Total Motor Speed: 46768 RPM
Vehicle Speed: 51.39 mph (82.56 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...


Or, with MT Badlands on 6s, I could use a 19t pinion and get a top speed of 52mph:

Differential Ratio: 4.090909090909091
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 54
Pinion Tooth Count: 19
Total Voltage: 22.20
Motor KV: 1580
Tire Diameter (inches): 5.84
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor Coil Resistance: 0
Spur/Pinion Ratio: 2.84 : 1
Total Ratio: 11.62679 : 1
Tire Circumference (inches): 18.35 inches (466.01 mm)
Rollout: 1.58:1
Total Motor Speed: 35076 RPM
Vehicle Speed: 52.41 mph (84.2 km/h)
Effective KV Value: 1580
KT constant: 0.86 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

And therefore, any setup I’d want to use with this would be possible with pinions in the range 12-20t. I know that 8s puts the 1717 slightly over its max rpm of 45,000 – but others have been doing it, so I’ll possibly give it a try.

I’d like to have reverse and esc braking, so I’ll either run 6s through a MMM or pick up a Mamba XL to run either 6s or 8s.


Next, I looked into various bodies for this and found myself looking at extra large 1/8 scale or 1/6 scale bodies with wheelbases from 16-18 inches. I don’t want to go as large as 1/5 scale with this because it would likely become too heavy for the 1717. I really liked the FG Jeep body, but found that it is currently unavailable in the US. Since I wanted to do something a little different than a pick-up body, I settled on the FG Hummer body. I like the size and the look of it. It has a wheelbase of 17.5 inches, so that’s the wheelbase I’ll build my truck to have:

http://i779.photobucket.com/albums/y..._4811Small.jpg

The FG truck itself with the Hummer body definitely has the monster truck look with very large tires and a wide stance:

http://i779.photobucket.com/albums/y...9_bigSmall.jpg

I’m thinking right now of setting mine up initially at least with a more scale-size tire look. I’ve mocked it up with MT Badlands:

http://i779.photobucket.com/albums/y..._4821Small.jpg


I might end up going with larger tires, but we’ll see.

Anyway, that’s the start of this project – I’m in no hurry with it, but hopefully will have it done sometime this summer to be able to run it in the nice weather.

I think it'll look great with the somewhat smaller tires, definitely gives it a more scale look. I'm curious to see how wide the body is in relation to the chassis and its track width, so measurements please?!? Either way, subscribed. Cool to see you starting another large scale.

This is going to be a very cool build, going by Brian's previous build.

Be very interesting to see how the 1717 handles the 8s, i have thought about running it higher myself.

Great now your giving me idea's...............

niiiiice, should be a very fun and cool looking truck :D

Sounds cool! May look more scale (and true to life) rolling on some phaltlines.

Nice project. This looks like a similar setup to what I hope to do once all of my R/C gear arrives here at our new home. I have two of those Hummer bodies as well. They are nice and big so they cover extended projects like this one very well. I like the idea of having a few options for the tires, because they can have very different effects for top speed and better handling depending on what you end up trying to do with the project. For just fun bashing the smaller tires will be a great choice. For high speed runs the larger tires give you more runout to get your speeds up. This should be fun to watch. I have been wondering how peoples drivetrains are holding up using these 1717's, because I picked up three of them before leaving Korea. I have not gotten to play with mine at all, but the mere size of these motors is intimidatingly emense when mounting them into a 1/8th scale vehicle.

I've been thinking that since I'm leaning toward the smaller tires I can start out with a slightly smaller spur gear, and use one of these new Maximizer aluminum diff cups I just picked up:

http://i779.photobucket.com/albums/y..._1080Small.jpg

One "unique" feature they have is that they take a larger ID bearing (10mm) because they are made a bit beefier than stock:

http://i779.photobucket.com/albums/y..._1082Small.jpg

I'm using an 8ight-T 50t spur gear and Sportwerks internals - so I shimmed everything inside properly and it fits nicely.
The 50t spur gear gives me almost as much flexibility as the 54 RC8T spur, and this way, I can either sell the RC8T diff if I don't use it, or drop it in later if I need it - only if I run 1/5 scale tires on 8s.

Here's what the CD looks like assembled:

http://i779.photobucket.com/albums/y..._1084Small.jpg

http://i779.photobucket.com/albums/y..._1085Small.jpg

I'm just waiting for new 100k diff fluid to arrive in the mail to fill this up (I used up the last of my old 100k fluid in my other large-scale CD).

looks very shiny and would be strong...

BUT i moved heaven and earth to remove that rubbish, weak 10x16x5mm bearing on the savage cups as it fails prematurely compared to the 8x16x5mm bearing.

So im using a vorza cup now with HD internal diffs... Just a heads up when your 10mm ID bearing fails.

Otherwise.. very shiny indeed :)

Or I could turn it down so the 8mm bearing fits!

Yea you could brian, thats what i wantedt to do with the IRC Cups... but they told me the alloy quality means that it has to be that diameter for a reason or it could crack and fail.

So turn it down but at a risk?

I wouldnt risk it as a lot of strain is put on those areas with brushless setups... especially that 1717!

I'll see how long the bearing lasts and go from there, I guess.

Edit: I could always enlarge the opening in the CD mount for one of these:

10x19x5 bearing

Brian, i was wondering why the inner surface of the cup doesn't look shining like the outer surface. Are they anodized or hard coated?

I wondered the same thing, but I'm not sure what it is - some type of rougher finish on the inside, though.

maybe just polished on the outside?

do you know the quality of the alloy? if it isnt a high grade, it could be very dull if not polished?

Jahay, they are 7075-t6.. and I believe that they put some layer of coating/anodizing on the inner to make it harder..

Speaking of 7075-t6 aluminum...here is what I'm making my chassis out of:

http://i779.photobucket.com/albums/y..._1095Small.jpg

It was a 12"x24" piece of 7075-t6 that I cut in half lengthwise. I have the other half as a spare if I mess this one up. :oh:

It's 4mm thick:

http://i779.photobucket.com/albums/y..._1093Small.jpg

I'm using flat plate for this build because I'll have more options for battery size and placement than I did for my other build using aluminum u-channel. Since I don't have the rails of the u-channel for strength on this one, I'll be sure to brace it well so it's nice and strong.

If you are using a hummer body, you should bling this chassis out and polish it to a mirror shine hah
interested to see how this takes shape!

How much?
 

How much did that 12" X 24" sheet of 7075 cost you, and where did you acquire it from? That looks like an interesting way to start out for a custom home made chassis setup. I kind of like the idea of starting from scratch and designing your own chassis the way you want it.

Couldn't pass up this deal on ebay:

http://cgi.ebay.com/7075-T6-Aluminum...item20b53c96d0

Very nice.
 

That is pretty good for $20, but is there anyway to varify the quality of the aluminum or to make sure you are truly getting 7075 T6? That should be a great piece of aluminum for making a very unique chassis for a great R/C project. Remember, measure twice, cut once. Good luck with your personal design.

Well, in the above picture (where the light reflects off of it), you can see that the aluminum has been stamped "7075-T6." I bought this from a store that primarily deals in metals, that I've bought from before, and that has excellent feedback. So, I guess I'm just going to trust them on this without further testing or verification.

Maybe use this as my inspiration:

http://i779.photobucket.com/albums/y...blingSmall.jpg

:lol:

haha wow that looks silly! but i can appreciate the work needed to drop it all the way down!

Oh brother???
 

Yea that does look silly. Kind of pointless wouldn't ya say? I bet it rides like crap to, because of the way they had to modify the suspension just to get it lowered like that. What a waste of a Hummer. Like you said I can appreciate the talent and the amount of work it took to do that, but for what? Sorry I am more of a practicality type person. All that flash for cash stuff is just stupid to me. Belive me when I was younger I used to put high value stereos in my rides, but one can only take so much loud music and the human ears were just not meant for that kind of punishment. I am sure that money could have been spent for a much more realistic facelift.

at least any thieves will have probs getting his 28" rims off haha

Catalytic converter.
 

Or the catalytic converter which have become so popular with thieves these days. From what I understand there is a very tiny ring seal of sorts made from a semi precious metal inside each converter that can be sold. Hardly seems worth the trouble of removing the converter, and then tearing the converter apart to me? Anyway kind of hard removing anything from the bottom of that vehicle now without putting it up on a lift.

That hummer probably has airbags which ride pretty darn good, hydralics have a sucky ride. It was also body dropped, body lowered over the chassis raising the floor. But yea, kind of a waste IMO too. Btw you don't have to take the catalytic converters apart, local scrap yards pay up to about $100 each as is. Sucks the theifs only have to invest in a jack and a cordless sawzall.

Back on topic. I'm curious, what's the width of the body?

Overdriven: I know you asked that before - I just haven't had the body back out of its box to measure - I think it's around 11" wide but will measure this weekend.

i got some 1/8th from the same seller a couple months ago for my custom chassis build. its def softer than normal 1/8th buggy chassis aluminum. and it bends a lot easier.

one thing i noticed is it doesnt take a countersink very well. its not a clean edge at least. it leaves a lip around the edge. its no my counter sink causing it because its a brand new 6 fluted bit. its almost like it pushed the alum out.



it bends my bumper back all the time if i tap into anything at the last bend to the left in the picture.

http://i63.photobucket.com/albums/h1...C/DSCN2879.jpg

completed chassis.
http://i63.photobucket.com/albums/h1...C/DSCN2993.jpg

Did you buy 7075-T6 or 7075-O? I guess I'll have to see how my piece works for my build.

I will say that from my experience 1/8" aluminum sticking out in front supporting a bumper will bend every time - that's what happened when I tried it with 6061-T6 anyways.

Edit: I checked out your build - I hadn't seen it before - nice work.

Here's what I'm currently doing - cutting pieces of 1/4" aluminum angle (1.5"x2") for a custom part of this new truck (this isn't the motor mount):

http://i779.photobucket.com/albums/y..._1098Small.jpg

ah, now that i look further in my archive of pics. its 7075-O softer stuff i suppose, right?



http://i63.photobucket.com/albums/h1...DSCN2832-1.jpg

thanks for the compliments, its been a long journey to get it running.

Yes, it is softer because it has not been heat-treated.

Yea it is annealed

Here's what I cut out of the 1/4" angle today. I still need to do some filing:


http://i779.photobucket.com/albums/y..._1111Small.jpg


http://i779.photobucket.com/albums/y..._1107Small.jpg



It's a bit beefier than stock - I may cut away some more metal, but my plan is to connect these shock towers through the bulkheads to the chassis with long bolts and connect my braces (whatever they end up looking like) directly to these shock towers.

Nice work
 

We can see where your going with this and I kind of like it. Just looking at your effots I can see various ways to do this. Its always nice to see some home made alternatives to most of the weaker stock parts that we have had to deal with over the years. Personally I like parts like this one to be beefier so they hold up better. Unless you are terribly concerned about excess wieght I would just leave them the way you made them at least for now. These types of projects take a lot longer, but always turn out better and can still be modified even more to make adjustments to suit ones taste in engineering, balance, and handling. Nice work, keep it up.

Nice work! I wish i could do this! THis is going to be awesome... i want to see more progress on this chassis.. quite intrigued as to how this will turn out.

You could easily do this - the only tools I use are a tabletop drill press, hacksaws, files, dremel, tap, and other hand tools.

The dimensions of the body are:

11.25" wide at wheel wells (widest spot):

http://i779.photobucket.com/albums/y..._1126Small.jpg

25.5" long:

http://i779.photobucket.com/albums/y..._1128Small.jpg

7.5" high:

http://i779.photobucket.com/albums/y..._1131Small.jpg

and compared to 4 year old girl:

http://i779.photobucket.com/albums/y..._1132Small.jpg

Thanks for the measurements and the size reference Brian!

haha awesome pics bud! Crazy how big that body really is!!!!