R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Nitro Off-Road > Offroad Nitro Engine Forum

Like Tree6Likes
Reply
 
Thread Tools Search this Thread
Old 11-12-2017, 12:48 PM   #1741
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

More progress.
I sat here thinking how I could add flywheel weight to the engine. Also, what if I DO use the buku clutch? It certainly weighs less than the big brass flywheel I made before so if anything I'll lose flywheel weight.
Here is what I came up with. I machined down the propeller hub that came with the engine. Up until now it's just been taking up space. It's pretty much hollow and doesn't add any weight. I machined it down because all I want is the center hub of it, which is keyed to the crankshaft. Now I can machine a large brass piece of metal to press that hub into.
This has a bunch of benefits.

1)Tons of flywheel weight.

2)A place to bump start the engine from easier.

3)I can use any normal flywheel now, standard aluminum or the Buku brass (if my clutch doesn't work out)




upload image to webside
timjs is offline   Reply With Quote
Old 11-12-2017, 01:27 PM   #1742
Tech Adept
 
Join Date: Jul 2009
Location: Florida
Posts: 158
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by timjs View Post
I installed the weights.
With these el-cheapo shoes, no extra weight, and .7mm springs I get engagement at 6,000rpm almost exactly.

With the weights added, it engages at 4,500rpm.

With the weights and .9mm springs, it engages at 8,500 rpm.

Obviously, I like 4,500rpm the best. IF I can get the engine to idle low enough. I'm sure it's simply a matter of having enough flywheel weight, but we will see.
Regardless, I just put in a Buku clutch order this morning and I'll use that instead if mine doesn't work. I always wanted one anyways.

best image hosting site
Cool, nice info..be interesting to see how you get that buku flywheel working, as I couldn't get my engine low enough to use a standard 34mm fly wheel. Think mine is somewhere around 38 or so. Also can't get engine to idel low enough for .7 springs , it's even tough for .9 springs as they still grab a little, could be my carb setup, but if messed around with it a lot. As Of now I like the 1.1 springs in the truggy.
speedworks is offline   Reply With Quote
Old 11-12-2017, 01:42 PM   #1743
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

Quote:
Originally Posted by speedworks View Post
Cool, nice info..be interesting to see how you get that buku flywheel working, as I couldn't get my engine low enough to use a standard 34mm fly wheel. Think mine is somewhere around 38 or so. Also can't get engine to idel low enough for .7 springs , it's even tough for .9 springs as they still grab a little, could be my carb setup, but if messed around with it a lot. As Of now I like the 1.1 springs in the truggy.
Not sure if you saw my post right after that one (it started the next page in the thread so you might have missed it).
My prop hub modification solves both of those problems (starting, idle).
I'm actually on the lathe right now trying to finish the part. I'm ready to just drive this thing.
timjs is offline   Reply With Quote
Old 11-12-2017, 02:38 PM   #1744
Tech Adept
 
Join Date: Jul 2009
Location: Florida
Posts: 158
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by timjs View Post
Not sure if you saw my post right after that one (it started the next page in the thread so you might have missed it).
My prop hub modification solves both of those problems (starting, idle).
I'm actually on the lathe right now trying to finish the part. I'm ready to just drive this thing.
Crap completely missed your other post lol. Now I see what your doing. Cool build, looks like it's coming along nicely. Definitely looking forward to track day!
speedworks is offline   Reply With Quote
Old 11-12-2017, 04:39 PM   #1745
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

Okay, here's the propeller hub so far. I machined it down so I can use the keyed hub portion. I made the brass section a VERY close slip fit on the hub. Any tighter and it would be a press fit.

Loctite 603 retaining compound curing now.

Once cured, I'll bolt it to the naked crankshaft, mount in the lathe between centers, and machine the O.D. concentric with the crank.

Then knurl it, since this is where the starter wheel will engage now.
The engine side has a small amount of stick out to give clearance to the bearing, and the flywheel side is flush.


ebay image hosting
timjs is offline   Reply With Quote
Old 11-12-2017, 05:32 PM   #1746
Tech Adept
 
Join Date: Jul 2009
Location: Florida
Posts: 158
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by timjs View Post
Okay, here's the propeller hub so far. I machined it down so I can use the keyed hub portion. I made the brass section a VERY close slip fit on the hub. Any tighter and it would be a press fit.

Loctite 603 retaining compound curing now.

Once cured, I'll bolt it to the naked crankshaft, mount in the lathe between centers, and machine the O.D. concentric with the crank.

Then knurl it, since this is where the starter wheel will engage now.
The engine side has a small amount of stick out to give clearance to the bearing, and the flywheel side is flush.


ebay image hosting
Looking good, wonder how much it will weigh compared to steel setup. Guessing you'll have more weight and will be able to get lower rpm for idle.
speedworks is offline   Reply With Quote
Old 11-12-2017, 06:13 PM   #1747
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

Quote:
Originally Posted by speedworks View Post
Looking good, wonder how much it will weigh compared to steel setup. Guessing you'll have more weight and will be able to get lower rpm for idle.
It's definitely heavier.
I'm thinking I can get a reliable 3-4k idle, making the 4500rpm or 6000rpm clutch arrangement work well.
These engines will idle down to 1500ish with s propeller.. it just shows it's all about flyweight.
timjs is offline   Reply With Quote
Old 11-13-2017, 05:21 AM   #1748
Tech Adept
 
Join Date: Jul 2009
Location: Florida
Posts: 158
Trader Rating: 3 (100%+)
Default

Quote:
Originally Posted by timjs View Post
It's definitely heavier.
I'm thinking I can get a reliable 3-4k idle, making the 4500rpm or 6000rpm clutch arrangement work well.
These engines will idle down to 1500ish with s propeller.. it just shows it's all about flyweight.
Sounds like it will work out great for ya. Wonder if the extra weight will cause slower revs. And if so, will it even be noticed. Looking forward to seeing how it runs!
speedworks is offline   Reply With Quote
Old 12-07-2017, 06:42 PM   #1749
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

Okay so I've been tinkering some more.
My propeller hub that I turned into a flyweight turned out nice. I got it mounted and did some test fires on a spare chassis as a bench test. Unfortunately, the D shaped key section stripped out and the flyweight was able to spin on the crank. Bummer.





So I decided to make a new flyweight but instead of machining down another prop hub to steal its keyway, I wanted to use a tapered collet system that we're used to using on our 2 strokes to secure the flywheel.

I machined the collet first. (I still need to slit it) It had to be custom made, because the section of the crankshaft by the front bearing is much larger than the typical flywheel collets you have in your pile of RC parts...
Then I made a new flyweight.

The flywheel itself is secured by being tightened up against the flyweight with a diamond friction disc. These discs are used in automotive engines to lock cam sprockets to the cams, and other high torque applications. It will not slip.

Testing soon first with my DIY weighted shoes, then with my Buku setup if the DIY don't work out.



timjs is offline   Reply With Quote
Old 12-07-2017, 11:53 PM   #1750
Tech Adept
 
Join Date: Jul 2009
Location: Florida
Posts: 158
Trader Rating: 3 (100%+)
Default

Looking good! Iv never heard of those disc before, but that should definitely hold it in place. Looks like that lathe is giving you a great surface finish!.
speedworks is offline   Reply With Quote
Old 12-09-2017, 11:16 AM   #1751
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

More bench testing. Trying to get an idle below 4,500 RPM because that's when my clutch engages. It seems that once I idle just a little too low, the engine actually starts running backwards at really high RPM and shoots a huge plume out of the carburetor. Has anyone else encountered this? It did not do this when I had the engine in my HPI bullet. It seems that the engine is bouncing off of the compression stroke right before it stalls and then starts running backwards. But I have 105 grams of flywheel weight at the moment.
Here is a video. It doesn't show the backwards thing, it's just a running video.
+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
timjs is offline   Reply With Quote
Old 12-09-2017, 12:57 PM   #1752
Tech Regular
 
timjs's Avatar
 
Join Date: Jun 2015
Posts: 365
Default

Success!!

The rpm is as low as it can go reliably. So I went to a larger clutch spring.

Here's a video of the engine idling (which it was for two entire tanks prior to shooting the video) and I can grab the clutch bell.

This is with el-cheapo aluminum shoes, with one tungsten-copper slug per shoe added for weight, along with .8 springs. The .7 springs in the last video were engaging at idle. They would likely work great with standard shoes, which are usually less than 2 grams. My shoes weigh 3 grams each.
Of course I still have Buku on the sidelines, just in case.

Once I get my chassis back from my buddy who is milling the engine mount slots ect, I'll put it all together and go for a test run!

Im excited! Sharkey, where ya at ???

I wish more people were active here still!

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
timjs is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
[FS] OS FS26S-C 4-stroke Engine squarehead R/C Items: For Sale/Trade 2 10-09-2005 06:22 PM
What is long stroke / short stroke engine? turboburns Electric Off-Road 18 10-03-2005 04:44 PM
Development of a new RC car Drift Electric On-Road 3 09-26-2005 09:41 AM
Development of a new RC car Drift Nitro On-Road 1 09-26-2005 08:43 AM
Development of a new RC car Drift Monster Trucks 3 09-26-2005 08:41 AM



Currently Active Users Viewing This Thread: 2 (0 members and 2 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 04:32 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net