Hippie's GTP Project
 

Im thinking about converting a 1/8 buggy based car. I have a couple of ?'s for those that have done it . What would be the best for racing single or 2 speed ?. Also what is the better car for racing . The ofna gtp or kyosho gt ?. I can get a used kyosho gt ( in very good shape) from my friend dave for $150.00 as a roller & it comes with a 2 speed . Then there is the ofna gtp with a single speed new for about the same price. There is also the ofne dm-1 spec a little pricy at $300.00 my cost . Im thinking i would use a MEDUSA motor on 4s. Which one would be the best choice ?.

I would go with the single speed if racing. My yusa with the 2 speed gets sideways when shifting under power. Fun when playing but i can see it being a big issue when racing.

By dm-1 do you mean the 1/7th scale car or the newer, shorter one with the std rear shocks and the pushrod front shocks?

The newer shorter one. What medusa on 4s would be goog for this project ?. I cant afford another neu :lol:.

60 - 2000kv should be good...

I'd love the DM-1 but not sure how easy to convert - the kyosho gt I thought was no longer made - A GTP2 would be easiest and parts are pretty easy as a lot is shared with the new LX1/MBX...

I agree with the motor choice, that would be the best bet. Only thing I do not like about the gtp are the k-sereis diffs. Not the best bet. Wish they had an upgraded jammin version with hyper diffs...

They now make the gt2 . But my friend has a gt in real good shape . Do you agree with linc that the single speed would be better for racing, than the two speed ?. The only way i can get the gt2 is to buy a rtr kar . whick i would rather not do .

Well I have the single speed pretty good - To be honest I have no issue with torque because of the brushless (1512 1Y). The only thing I wanted a two speed for was more top end speed. 60-70+...

But then I'd have all the pain of pinions etc so for me single speed I think is fine... I just need to get my but into gear to paint my new 350z body...

Would the motor you recomended still be good with a single speed ?.

I ran my GTP the other day on 4s (set up for 10s, but the cells aren't in yet), and even though it wouldn't get fast enough to shift, it was really hard to keep from spinning those tires. Then, this evening (in between bouts of rain), I made up a quick-n-dirty harness to tie 4 2s packs together just to see. Well, I got it to shift all right, and what people say about on power shifting is correct; all 4 tires broke loose and started to fishtail. Was able to get it under control, but barely. Man, this thing was FAST (no GPS or radar to verify)!!! I'm sure the damp road conditions didn't help.

If you go with the 2 speed, make sure you have really sticky tires. It might help to keep the difference in ratio closer together so there isn't such a drastic change in rpm/torque when it shifts.

Thank's for chiming in brian . If thats the case maybe i'll just get a single speed car. It's looking like the ofna gtp is the leading canadit . since my friends kyosho has a 2 speed that i would have to lock in gear . I can get a really good price on the gtp . Do you agree with the MEDUSA motor recomended eairler in this thread . This would be run on 4s .

60 - 2000kv should be good...

People say the 60mm will be fine, but I personally would go with the 70mm version when it comes out. The GTP is a fairly heavy vehicle (at least mine is) and geared tall enough to hit higher speeds with one gear will put a decent load on it.

Again, for something that will be going fast, I would probably mate a 2000 kv motor with 5s. For 4s, I would run a kv of ~2500. I like higher rpms when geared tall, because the ESC may have trouble getting rotor position on take-off, which may cause cogging. A faster motor geared right should take off smoothly and have decent top end. The Medusas are rated upwards of 60k rpm, so 40k+ should still be well into the efficiency range.

I only have a 4s pack & would rather not buy a new pack . My buggy uses a 2550 kv motor on 4s & runs great . Do you know when the 70mm medusa's are going to be avalible ?. Also i noticed your gtp2 has a chassis brace connected to the diff's not the chassis . The gtp car has a rear chassis brace connected to the chassis that looks a little different than normal bracs. Will this cause a problem wtih mounting a motor ?.

The chassis brace connecting all the diffs was custom. I've found that the normal F/R braces that angle down to the chassis still allows flex. With the brace I made, there is MUCH less flex. The stock rear brace on the GTP attaches to the radio box. I imagine some type of custom brace will need to be done so it is on the other side of the driveshaft (otherwise would interfere with the motor). Pic showing the crappy rear brace layout:

http://www.ofna.com/images/UltraGTP/...tr-top-big.jpg

Brian i just looked at the medusa motor on your calculator . The 60mm motor only goes up tp 2000 kv. Do you know if they make a larger kv motor ?.

Not that I know of. That's one of the odd things about Medusa; their kv ratings don't go high enough for each range of motors IMO. For instance, I'd like a 60mm one for my Slash running on 3s, but the kv as you see only goes to 2000. I have to step down to a 50mm to get the kv I want. I'm sure it'll be fine but...

I would wait to see what others say though. I've never run a Medusa, but the little I saw the wires seem kinda thin compared to Neu or even Feigao. They seem to run ok though. For $100, I suppose you could run the 60mm 2000kv on 4s and see how it goes. If their present models are any guide, their 70mm motors will probably only go up to 1200-1500kv.

I just found there site . They have two new 60mm motors listed . One is 3100kv & the other was around 2200kv. They also had there 70 mm motors listed They went up to 2300kv .

Oooh, 3100kv! Perfect for me. :smile:

IMO, the 2300kv 70mm would be perfect. Otherwise, the 2200kv 60mm would be my next choice. Actually, you might think this is crazy, but the 3100 60mm on 4s geared down would probably work quite well too. Yeah, it would be spinning close to 46k rpm, but that should be just fine. Would be taking a page out of Novaks book (use a smaller motor that revs high instead of a larger lower-revving motor). Might want to check Griffins motor calc to see where the efficiency starts falling.

Dang, the 70mm motors sell for under $125... You can't go wrong there.

I would like the 1200kv model to run 10s on, maybe with a pair of 5s rhino lipos... That would be a cheap setup, and pair it with lutach's 10s esc... Under $500 bucks for a hv car system!!!

I just had my friend dave order me a OFNA ultra GTP . I will be using the medusa 70mm 2300 kv motor on 4s. What size pinion would be good. Im came up with this using a 13t pinion .


Differential Ratio: 3.142857142857143
Transmission Ratio: 1
Other Ratio: 1
Spur Tooth Count: 49
Pinion Tooth Count: 13
Total Voltage: 14.8
Motor KV: 2300
Tire Diameter (inches): 4.5
Tire Ballooning (inches): 0
Motor Current Draw: 0
Motor coil Ω: 0
Spur/Pinion Ratio: 3.77 : 1
Total Ratio: 11.84615 : 1
Tire Circumference (inches): 14.14 inches (359.08 mm)
Total Motor Speed: 34040 RPM
Vehicle Speed: 38.47 mph (61.79 km/h)
Estimated Adjusted Speed: 37 mph (59 km/h) - 5% loss
Effective KV Value: 2300
KT constant: 0.59 oz-in/A
Motor Torque: Amperage not specified...
Final Torque: Amperage not specified...
Final Power: Amperage not specified...

Well, the tires on my GTP are closer to 4.25", which will drop the speed to around 35mph. You can use a 14T pinion to get back up to ~37mph. I don't think you'll have any problems with a 15T (~40mph) or maybe even a 16T pinion (~42mph), if the vehicle is kept light. But, a 14T pinion is a good place to start.

Well i ordered my GTP today. It will be here friday . I plan on using the RC-monster motor mount with a MEDUSA 70mm 2300kv motor on 4s flightpower lipo with a MM esc.

Changed thread title per OP...

Thank you BRIAN :smile:.

These GTP kits are becoming quite popular. Not surprising since the rollers are pretty cheap.

Post some pics when you can, rchippie.

I plan on using 5.5 mm plugs . Sinice the motor i will be using has a max amp draw of 100 amps. Does this sound good ?.

The 5.5mm plugs will work fine. I use them on the 1515/1Y in my GTP. They are rated for 150A constant. You could probably get away with 4mm plugs, but the less resistance the better.

I knew they would be . I just like confermation on my descions :lol:.

Hmm I'm running a 1512 1Y 2650kv on 5s with 20/22T pinion.... I think i might be geared for a little more speed...

Brian i found this upgraded brace .

http://www.nitrohouse.com/catalog/pr...6e0eaa933db736

Those braces in your link are just upgraded versions of the stock setup - probably lighter. No matter what, you're gonna need to come up with a different rear brace scheme because that is right where the motor goes - unless you find another location for the motor somewhere...

Okay :smile: The guy at nitro house told me the upgraded brace would bolt directly to the chassis & not have to mount to the box . I'll figure something out :lol:.

The front one yes, but the rear one just looks like a lighter replacement judging by the shape. He could be right, but it doesn't look like it to me...

This is what I did - Custom rear brace and an old MBX front brace (in addition to gtp brace) - Rock solid and no issue for motor placement

http://i168.photobucket.com/albums/u180/Arct1k/001.jpg

Brian & chris how thick are your braces ?. Thats looks like what im gonig to have to make .

I used 1/8 as that is what I could get at lowes...

I got my GTP today. I all ready mounted the RC-MONSTER MM . I trying to decide if i want to make my own battery box out of kydex or buy one from mike .

If you can make your own you should. It's much more satisfying.

Here are the first few pics .

I really like the battery box idea i came up with .

http://skellyo.com/hippie/gtp/

That adjustable battery box is pretty sweet. Nice job. :yes:

thank's but it's acctually not adjustable it just looks that way :lol: . This box is made for FP lipo . It is also long enough to fit the zippy R lipo in case i decide to get one latter .