Project Thumper (aka Four Stroke Maxx)

[deaconblue23]

Well I made a trip to Lowe's this evening for some supplies for our saltwater pool (more or less for truck parts, couldn't tell the wife that though ). I got longer bolts, some 1" standoffs will cut them if I have to, lock washers and flats, and a fresh tube of blue loctite. I really did not like the way the engine was lining up so i machined down the mounts we will see how it works out. Pictures will be up soon!!

Aluminum bulkheads why would I want to do that. Then my plastic A arms would look trashy!!!! The guy I got the chassis from has them on eBay, I might look into them later, my wife is having a cow over how much I spent just to get the parts I have now.

 

[abadk9420]

Looks like this is going to be a sweet project when you get all together, just one question, if this is a 4 stroke engine then why does it run on "standard 2 stroke nitro methane."

 

[deaconblue23]

Because it does? :\ Really dont know but all small 4 strokes run on it, most planes run on 10% to 15% nitro though. This engine will be running on 20% or 30% I will start on 20% though. I guess its kinda like 4 stroke string trimmers they still use 40:1 gas oil mix.

More pictures, probably the last post till Friday. Tomorrow is payday though!

 

[olds97_lss]

More than likely due to the size of the engines. Running anything but really high octane fuel with nitro in it wouldn't give you the power you need to keep it running. Those tiny combustion chambers don't give you much room for a fuel/air mixture. So running highly oxygenated fuel (nitro infused methane) gives you more bang for the smaller chamber.

I've seen a few that were converted to diesel. They ran, but not nearly as peppy as NitroMethane.

 

[traxxas t-maxx]

What are you doing with the old nitro motor.

 

[deaconblue23]

It is sitting on my work bench right now. I do not know if I am going to keep it or what I have not taken it apart to look at the piston, rod, and crank yet. So as for now it sits.

 

[traxxas t-maxx]

Well if its still good and you don't want it talk to me.

 

[deaconblue23]

Time for an early morning update!!! I have got the engine mounts machined and lifted to where I think they need to be, also got the fuel tank shimmed and mounted. Now on to the pictures!!!!

The only real issue I have found right now is that with the new thicker chassis I have to find some new screws to mount the tranny. The screws I had only go into the tranny by two or three threads and that is not near enough for my liking.

 

[Lessen]

Lookin' good Deacon. Are you planning on running that pipe? It might be pretty restrictive for a two stroke. If you want to quiet the engine down a bit O.S. makes an exhaust for the smaller 4-stroke engines.

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXF36&P=7

This might be the right header for your application...

http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXXF14&P=7

 

[deaconblue23]

Actually I do not know about the pipe yet, will just have to see. As far as the header goes all it is right now is steel brake line I was just going to use my tubing bender and then flare it out to make it large enough to fit the pipe if I am going to use it at all. I am pretty sure that it is a single chamber pipe. We will just have to see how it works out. Right now it is a lot of trial and error. Luckily enough I just love to tinker on things til I get it right. I just finished up replacing some of the wiring on the truck evidently mice like wire insulation , that is what I get for leaving it in my storage building all winter I guess. :\

 

[Metalhead Matt]

Mice are destructive! The truck looks great Deacon. I will be scooping your thread for a test rip. I've seen a couple 4 stroke Maxx's and they where all pretty slow. But I have no idea how they where geared. You seem to have that figured out enough for some testing, and by how clean of a project you have, I'm sure you'll get it figured out. Keep up the great work and best of luck!

 

[deaconblue23]

I now have all the electronics rewired and installed, still bending pipe to get the exhaust done. I am having trouble getting the bends tight enough, the good thing is pipe is cheap! Might try and have some pictures up this evening. Does anybody have any thoughts or reasons why I should or should not use my t-maxx exhaust pipe that is in the pictures. I am open to any ideas or thoughts on upgrades that I might need. After all this is a learning process for me and hopefully everyone following the build.

 

[olds97_lss]

Well, if it's a 3.3 maxx with revo style diffs, then no. Other than bulkheads, it should hold up ok. If it has old diffs... then with a torquey engine, you may have diff failures more frequently.

Do you have a fuel pump/regulator? Don't 4-strokes need that to run right?

 

[deaconblue23]

Actually from the home work I have done 4 strokes have pretty good "draw" on the intake stroke. Some do not even need a pressurized fuel tank, they will pick it up on its own. Yeah I am afraid the diffs will not hold but I plan on taking it easy the first couple of runs, at least till I get used to it and how "differently" the 4 stroke will behave. I did calculate it earlier and since it is .26 cubic inches it figures out to be 4.28 cubic centimeters. I have been looking at aluminum diff cups on fleabay to see if I can find a good buy, after I get them I will just seal the diffs and pack them full of synthetic grease!

 

[olds97_lss]

Huh! Didn't know that.

I was following a thumper revo build a few years ago and he was having fuel delivery issues until he found the right pump/regulator for it. May have been a different style of engine or something.

Wish I could find that thing again. He had race footage of it. Was cool to see/hear the thumper in the mix with all the other 2 cycle rigs.

EDIT:
Found it!
http://video.google.com/videoplay?docid=-4531439947363954250&hl=en

 

[deaconblue23]

That is one thing I am looking forward to is gobs of torque, a lot of people say "they dont have the horsepower!" but torque is what gets you out of that turn quicker, and also off the line like a bat out of hell! horsepower doesn't really mean squat on a really curvy track, just on the straights where you can rev that 2 stroke to the moon!

That video is sweet, I am glad to see the revo holding its own. And it just sounds so cool compared to all the 2 strokes, sounds like a little motorcycle or 4 wheeler. Thanks for finding that it was very cool to watch it!

 

[olds97_lss]

Thought maybe that would get a spur under your seat to get yours going!

If you notice, there were 3 or 4 other vids of the race as well.

 

[deaconblue23]

Yeah I book marked that video and when I have time (HA that is funny!!!) I will watch the rest. I would have it done by now but I work to much, plus I must tend to wife every now and then they need attention too you know!

 

[deaconblue23]

Well I just won some new Revo spec diffs off of fleabay, I got to thinking about what you said and I might as well get them so when I need them. As far as the bulkheads go I might wait until I tear up the ones that I have now, just have to wait and see.

 

[olds97_lss]

Well, I have no idea the compatibility from maxx 2.5 to maxx 3.3 or revo diffs/axles/bearings. I have a feeling you may need more parts to use those diffs in an older style maxx, but I could be wrong.