Spektrum DX7 on a Tmaxx

[jojoviudez]

Today I took off the 3 channel receiver from my tmaxx and will be experimenting using a spektrum dx7 radio paired with an ar6100 receiver to control the tmaxx. I used to fly a slowstick before getting the tmaxx, and i really liked the strong performance of the dx7 radio so I decided to try it out. The immediate problem I resolved crudely is with the throttle. Instead of a trigger type control from the TQ3 radio controller, the dx7 has stick controllers, just like some old tamiya remote control cars did. so i needed a way to have the throttle go back to zero or the starting point. i dont want to open up my radio just to put a spring in there, so i used a simple rubber band and viola! the throttle servo goes to throttle, the steering servo goes to aileron and the forward/reverse servo goes to aux. i have yet to try it outside, but its a foggy day in anchorage alaska. I'm pretty sure its gonna work, i tried a servo test and it worked ok. i programmed one switch to act as a throttle kill since i don't want it to be still running once i'm done. i am quite eager and excited to try it outdoors. I'm sure there will be lots of trimming, but once that's done, i'll be all set.

 

[jojoviudez]

It worked! I drove the tmaxx yesterday and I felt more confident using the dx7 compared to the 27mhz radio that originally came with the tmaxx. No glitches as expected of a 2.4ghz transmitter. I don't drive the truck to where I can no longer see it, this setup really works for me. I never did get used to the pistol grip controller anyways. I used to have an old cheap rc that uses the stick control, and I liked that alot. I will be using the dx7 on my tmaxx from now on. Goodbye to long antenna's.

 

[Rolex]

There was a time that ground and air frequencies were strictly controlled and not interchangeable, but that's changed with the 2.4 technology.

 

[jojoviudez]

There was a time that ground and air frequencies were strictly controlled and not interchangeable, but that's changed with the 2.4 technology.

I agree with you Rolex. Computer radios nowadays is really getting sophisticated every time a manufacturer introduces a new model. Too much technology for me thou. I'm just happy to have an integrated timer and a model match on the transmitter, and ofcourse 2.4 ghz is the way to go. I wonder what frequency will be the next step higher? Or will there ever be one. Anyway, I took my tmaxx 3.3 out tonight and I am impressed by the power. It was too much power that it always wants to go wheelie on me. I will have to program the dx7 to lower the throttle a bit and with a flick of a switch go WOT whohooo. I don't race but this is my idea of fun for now! I took some photos that I would like to share. Hope you like it.

 

[Metalhead Matt]

Two of your tires are on backwards. This makes them more likely to rip. Nice lookin' rig. Is that a stock 2.5 pipe? Swapping to the new resinator would really open that 3.3 up. You could always step up a tooth or 2 on the clutch bell if it's wheeling to much for your liking. Backing the slipper off helps as well.

 

[jojoviudez]

Two of your tires are on backwards. This makes them more likely to rip. Nice lookin' rig. Is that a stock 2.5 pipe? Swapping to the new resinator would really open that 3.3 up. You could always step up a tooth or 2 on the clutch bell if it's wheeling to much for your liking. Backing the slipper off helps as well.

Thanks for noticing the wheels, I was in a hurry to run it that I mixed up the wheel direction. I'm guessing it's the stock 2.5 pipe, i got this 3.3 used and alot of trimming and screws needs to be replaced. otherwise it's a strong 3.3 so far. I'm not into racing as I just enjoy running it as it is. however I did buy a rubber coupling and attached it to the pipe exhaust pointed it downwards, thinking i could minimize the noise. but i guess it did not. it's louder than my trx.15 tmaxx. I have attached the wheelie wheels that came with it. and i have yet to enjoy those wheelies. today i tried to run it, but it would'nt start and i ended up flooding the engine and wasting fuel since i could see it spit out of the exhaust. i'm back to finding out what's wrong and i may have to tear down the engine since the pullstart is not retracting all the way back and feels like its sticky or gummy to touch. must be something dirty in the engine. I'm using blue thunder 20% nitro. I'd like to ask if I can use Byron's 15% nitro and 18% oil with the tmaxx 3.3? I'm learning as i go with this nitro engine stuff, I am enjoying but it's a tedious thing to tear down, clean and then rebuild. but there is something about the nitro smell that is definitely addicting.

 

[Metalhead Matt]

I think your current fuel is most of your problem. Byrons 20% is my favorite. Never checked the oil content. It's a lot less oily than some other brands. Take your p/s off and clean the one way bearing really good. Use brake cleaner, carb and choke cleaner, ect... Unless you have some nitro cleaner lying around. Change your glow plug, make sure your ignitor is charged all of the way and it should run better for ya.

 

[jojoviudez]

I think your current fuel is most of your problem. Byrons 20% is my favorite. Never checked the oil content. It's a lot less oily than some other brands. Take your p/s off and clean the one way bearing really good. Use brake cleaner, carb and choke cleaner, ect... Unless you have some nitro cleaner lying around. Change your glow plug, make sure your ignitor is charged all of the way and it should run better for ya.

Thanks for the tip. I will do that today. Byrons fuel is expensive at LHS at $16 compared to blue thunder around $12. The engine revs and pulls very good....once it starts....and that's a hit and miss arrrrghhh. But I agree with you about the Byrons 20%, that was my first fuel choice before I switched. That one started right away for me.
so do you think Byrons 15% nitro and 18% oil will work?

 

[Rolex]

I totally recommend the 20%.

 

[Foolproof]

Me switching from Top Fuel 20% to O'Donnells 20% I could see a change. I wish my lhs had the Byrons and I would use it. Havent seen any - comments about it.

 

[olds97_lss]

I've run many fuels and like byrons the best. $18 a gallon? I wish! I buy 25% nitro which I think has 10 or 11% oil in it, $30 a gallon (maybe more, i don't pay attention).

I've run trinity MHP, blue thunder, traxxas, hpi, wildcat, odonnells and byrons. Out of all of them, byrons is at the top with trinity at second. Didn't care for the rest. Too oily.

 

[jojoviudez]

I've run many fuels and like byrons the best. $18 a gallon? I wish! I buy 25% nitro which I think has 10 or 11% oil in it, $30 a gallon (maybe more, i don't pay attention).

I've run trinity MHP, blue thunder, traxxas, hpi, wildcat, odonnells and byrons. Out of all of them, byrons is at the top with trinity at second. Didn't care for the rest. Too oily.

I will definitely give trinity a try if i find one at LHS. there are only 2 hobby stores in anchorage. byron fuel is about $18 a quart regular price. they are giving 20% discount because LHS is moving to a new location. thanks for the info.

 

[olds97_lss]

OOOoooooooohhhhhhhhh... $18 a quart! Thought you meant a gallon! lol

 

[Metalhead Matt]

Ouch. I'd find some buds to go in on a bulk shipment. That's twice as much as we pay here at the lhs.

 

[jojoviudez]

Update on using the spektrum dx7 on the tmaxx 3.3:
The control is still tricky, especially the throttle trim. But I notice when the battery becomes low, the throttle servo goes WOT. I'm using 4 AA nimh 2000 mah. My question is, how long do they normally lasts using 3 tmaxx standard servos connected to a receiver? But I am getting used to it thou.
On a side note. Today, I got a good deal. I bought 2 gallons of byrons fuel for just a whopping $20!!!! I think it retails for $32 per gallon here in alaska. Looks like i'll have enough fuel to finely tune my 3.3 if it will ever hold a tune hehehe.

 

[Metalhead Matt]

If it doesn't hold a tune, it may need sealed. You'd be much better off with a 5 cell hump pack. The 4 aa's your using only puts out 4.8 volts. That's the minimum required to run your electronics. A quality 5 cell hump pack runs about $10-15.

 

[Rolex]

I notice when the battery becomes low, the throttle servo goes WOT.

That's exactly the reason you need a fail safe.

 

[jojoviudez]

That's exactly the reason you need a fail safe.

I agree, a failsafe is a good device to have. I read this here at rcnitrotalk on another forum. Are those cheap failsafe from ebay any good? Or do i need to shell out for a quality failsafe unit? I think these should be standard features for receivers.

If it doesn't hold a tune, it may need sealed. You'd be much better off with a 5 cell hump pack. The 4 aa's your using only puts out 4.8 volts. That's the minimum required to run your electronics. A quality 5 cell hump pack runs about $10-15.

I have the 5 cell hump pack for HPI but I dont have the charger. I think I will look for a 7.4 v lipo and figure out how to install it on the tmaxx.

 

[Macguyver]

i bought a couple of the cheap ebay failsafes just to see if they work .....and they do work ...but i havent tried them in the truck while driving ....???how reliable are they ????? i dont know ...but they do work

i use a duratrax one in my truck ....will try the cheap ones in my other truck

 

[jojoviudez]

i bought a couple of the cheap ebay failsafes just to see if they work .....and they do work ...but i havent tried them in the truck while driving ....???how reliable are they ????? i dont know ...but they do work

i use a duratrax one in my truck ....will try the cheap ones in my other truck

where have you triied the failsafes on an airplane or a car? if you say they work i will definitely get me one of those cheap failsafes....as soon as the wife grants me access to the credit card hehehe. your duratrax is a name brand one, i'm sure it costs more but if it does its job well then I'm sure its very much worth it.