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My Savage's new 21cc powerplant

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Old 10-18-2008, 09:12 PM
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neoseekers
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Default My Savage's new 21cc powerplant

I thought I quit this hobby years ago. I wasn't too thrilled about re-powered it with another nitro motor and I couldn't justify converting to a brushless/lipo system just yet. I had a spare Echo motor for my trimmer, but the trimmer will never die. Why not try to revive the old Savage.

Check out the final test run. I'm back in action again.
http://www.youtube.com/watch?v=_JqRfJfbqOg
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Old 10-18-2008, 10:16 PM
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Default RE: My Savage's new 21cc powerplant

nice!

now if only it was still strong enough to bash[>:]
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Old 10-18-2008, 10:18 PM
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Default RE: My Savage's new 21cc powerplant

you'll need to make an aluminum roll cage for the fuel tank!

but nice work there
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Old 10-19-2008, 12:28 AM
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Default RE: My Savage's new 21cc powerplant


ORIGINAL: neoseekers

I thought I quit this hobby years ago. I wasn't too thrilled about re-powered it with another nitro motor and I couldn't justify converting to a brushless/lipo system just yet. I had a spare Echo motor for my trimmer, but the trimmer will never die. Why not try to revive the old Savage.

Check out the final test run. I'm back in action again.
http://www.youtube.com/watch?v=_JqRfJfbqOg
Very nice! good fabrication in making the pan to hold the gas 2-stoke engine.

BTW, what displacement is taht Echo? A 25cc?
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Old 10-19-2008, 12:52 AM
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Default RE: My Savage's new 21cc powerplant


ORIGINAL: SAVAGEJIM


ORIGINAL: neoseekers

I thought I quit this hobby years ago. I wasn't too thrilled about re-powered it with another nitro motor and I couldn't justify converting to a brushless/lipo system just yet. I had a spare Echo motor for my trimmer, but the trimmer will never die. Why not try to revive the old Savage.

Check out the final test run. I'm back in action again.
http://www.youtube.com/watch?v=_JqRfJfbqOg
Very nice! good fabrication in making the pan to hold the gas 2-stoke engine.

BTW, what displacement is taht Echo? A 25cc?
lol read the thread title
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Old 10-19-2008, 01:29 AM
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Default RE: My Savage's new 21cc powerplant

oh, I missed the measurement units behind it. I was under the impression he took an old Savage .21ci and modded it to mount the weed eater engine
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Old 10-19-2008, 02:53 AM
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Default RE: My Savage's new 21cc powerplant

funny though.....it STILL sounds like a weed wacker....
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Old 10-19-2008, 03:56 AM
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Default RE: My Savage's new 21cc powerplant

Nice,im doing basically the same thing except the 26cc engine connects straight to the hpi 2 speed,nopt with the gears giving me a total ratio of 7:5:1.What is tyour total ratio?In case you dont know what that is would you be able to tell me howmany teeth is on the pinion and spur gear?
Since i have a feelling my ratio wont give me enough top end.
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Old 10-19-2008, 09:33 AM
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Default RE: My Savage's new 21cc powerplant

Looks cool. How's the chassis flex? Looks like if it flexes you will lose you gear mess and chew up the spur. Some supports in the vertical (like the original TVP's) may be an option.

I like it.
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Old 10-19-2008, 10:37 AM
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Default RE: My Savage's new 21cc powerplant

i need to see a video of that whipper snapper.....very nice vid. nice job on that project[sm=thumbs_up.gif]
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Old 10-19-2008, 10:46 AM
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Default RE: My Savage's new 21cc powerplant

now if only it was still strong enough to bash[>:]
I've bashed the hell out of it and only broke the servo because the spring was too tight. I am ordering the cheap MG559 servos from China.

funny though.....it STILL sounds like a weed wacker....
It actually has a nice deep monster truck tone, not like those 4 cylinder imports.

What is tyour total ratio?
The tranny is single speed. I used a 49T on the motor and 49T on the spur. 7.5:1 ratio. Fast, but not impress with the hole shot. I put and 34T on the motor. The motor is sitting on 4 bolts so I can raised to lower it so it sit nicely on the spur gear. I try to get a photo so you'll see what I mean. About 11:1 gear ratio works better for me, but lost some top end. I thought about upgrading to the 2 speed tranny. What is the gear ratio for first and second?

How's the chassis flex? Looks like if it flexes you will lose you gear mess and chew up the spur
The chassis is extended with a 5in angle bar with the motor plate for support. The gears are still line up so it looks like the chassis is holding up.
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Old 10-20-2008, 04:36 AM
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Default RE: My Savage's new 21cc powerplant

Im not to sure on the tranny ratios,in second gears,in first gears it is roughly 2:1 biut that is really rough.
Really 11:1 works better.Thats funny,I heard people saying around 6:1 is a good ratio.What is your top end on the 7 :5:1 approx?
Also i got the mgg995 servo on mine for $10 each,and they are strong though weith ym radio glitchy for some reason,hopefully yours will be good.
Also what ratio is the video of?You should get some videos of topspeed runs.
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Old 10-20-2008, 03:02 PM
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Default RE: My Savage's new 21cc powerplant

The ratio in the video is 11:1. Very slow on the top end. Then again I don't need speed. I was thinking about getting a 2 or 3 speed tranny. My only concern is shredding the gears when shifting since these gas motor have so much torque. Here are the specs I've found for the tranny.

2-Speed
1st Gear: 18/44*32/29 = .45141 = 2.22:1
2nd Gear: 23/39*32/29 = .65075 = 1.54:1

3-Speed
1st Gear: 18/44*31/30 = .42272 = 2.37:1
2nd Gear: 21/41*31/30 = .52927 = 1.89:1
3rd Gear: 24/38*31/30 = .65263 = 1.53:1

I had some servo glitches when I ran long wire for the kill switch. I shortened the wires and it solved the problem.
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Old 10-20-2008, 07:42 PM
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Default RE: My Savage's new 21cc powerplant

Yes, the 2speed & 3speed trannies will not hold up to the torque of a gas engine. I am of course estimating your gas engine is producing just a little more than 1ft-lbs (say, like 200in-oz). Hpi uses cast gears for the most part inside their trannies. These might gears might withstand adound 100in-oz before you risk stripping them (that is a guess, I have not actually done any experiments on them).

Machined and hardened gears (like how Robinson Racing makes their steel spurs) should be up to the task. But the problem would be machining and treating the gears to take the same shapes as the stock tranny gears.
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Old 10-21-2008, 11:54 PM
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Default RE: My Savage's new 21cc powerplant

I have the 2 speed in mine if i can get it to shift(due to gas engines turn opisite way of nitros,and with less rpms),it will be great,should sugnificanlty make the top speed higher.
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Old 03-20-2018, 08:56 PM
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Default Hey there every one

Im on the same boat im looking to convert my savage x as well i have it all set up and layed out just dont have a clue on how to after hours of looking in forms web pics videos ive seen sone beautiful conversion done i was hoping tou can share some ligth idk if my motor is to big nor if the motor configuration layout is the ideal one for me but im really exited to build it please help
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