• If you have bought, sold or gained information from our Classifieds, please donate to HomeBuiltAirplanes and give back.

    You can become a Supporting Member which comes with a decal or just click here to donate.

Two Weedhopper (B?) Propellers for Two Chotia 460 engines

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

choppergirl

Banned
Joined
Jan 30, 2015
Messages
1,682
Location
air-war.org
I need two Weedhopper type (preferably helical twisted) propellers for two Chotia 460 engines (which I bought for $99 with my Chotia Woodhopper)

The construction manual says start with a 36"x14", but I think longer with less pitch is suppose to be better and quieter(?)

I believe at least the Weedhopper B model ran the Chotia 460, maybe later ones too...

4 bolt hole pattern on the prop.

Broken propellers: actually, if anybody has a broken Weedhopper helical twist propeller for a 460 they wouldn't mind donating to me, with at least one good side, that I could use as a template to make some new ones, that might work too, as my dad has a cabinet shop, and I could reimburse you for shipping.

~

Also, I need two exhausts, and two carbs (Walbro/Tillotson/ (Bing 54?))... the carbs, I can get on eBay... the exhausts... not so sure what I need yet.

If you know what exhausts 460's take, and/or where I could get them, let me know. I have the 460 manual, and also the 460 assembly/rebuild video from youtube. (Also the Woodhopper plans).

http://dcim7.peachcountry.com/DSC_0662.JPG

http://dcim7.peachcountry.com/DSC_0655.JPG


So like, keep your eyes out for me.... I think a lot of Weedhoppers were made, so I think this stuff should be out there.

If you've had lots of experience running 460's in the past, or want to set me straight on something on the above, reply to this thread, or PM or email me with your experience and tips.

Thanks.

CHOPPERGIRL
 
Last edited:

wakataka

Well-Known Member
Joined
May 1, 2013
Messages
94
Location
Redding, California
Weedhopper prop diameter is somewhat limited by ground clearance but also by prop tip speed. I don't recall what the RPM of the engine was but it is a direct drive, so the prop turns a lot faster than on reduction drive engines. When the prop tips approach 85% of the speed of sound, the prop efficiency drops off the chart.

Here's a good reference for calculating prop tip speed:

http://www.epi-eng.com/propeller_technology/selecting_a_propeller.htm

The Chotia 460 didn't come with a tuned exhaust. It just had a short (maybe about 6" as I recall) straight pipe. It was loud as all get out. I made a kind of muffler which consisted of a streamlined 'can' welded around the pipe with a bunch of small holes in the bottom and the trailing edge of it. It quieted the engine down some and didn't seem to have any effect on the power output. I'm sure the engine could produce more power with a tuned exhaust but I don't think Weedhopper ever sold one for it. Because it turns slow, it would need a longer resonance chamber than a Rotax, which would result in a big (and heavy) tuned exhaust.

Here's a copy of the engine manual from Weedhopper

http://ulav8r.com/weed flyers files/Chotia-460_NewManual[1].pdf

It lists a 44x19 prop.
 

Mark Z

Well-Known Member
Joined
Aug 29, 2012
Messages
820
Location
Granbury, Texas USA 0TX0
I've had friends that owned Weedhoppers with the Chotia engines and had off airport dead stick landings. Both of the Chotias were replaced with a Rotax 503 (I think).
 

wakataka

Well-Known Member
Joined
May 1, 2013
Messages
94
Location
Redding, California
I've had friends that owned Weedhoppers with the Chotia engines and had off airport dead stick landings. Both of the Chotias were replaced with a Rotax 503 (I think).
The Chotia engine was a work in progress. I flew one for over 50 hours and it was about as reliable as the chain-saw and go-kart engines that were the norm back in the early days. That's not saying much. Off-field landings were to be expected. The climb rate on the Chotia powered Weedhopper was very marginal with a 200 pound pilot on a hot day. Sometimes I'd have to wait until a thermal kicked off in order to get above the hedgerow to the next field. I wouldn't want to fly one over any unlandable terrain. And it vibrates like a hypothermic chihuahua.
 

choppergirl

Banned
Joined
Jan 30, 2015
Messages
1,682
Location
air-war.org
A super nice person mailed me some rudder pedals and 60 lbs of airplane magazines today. He also sent me a box of some aircraft rivets which turned out to fit... right diameter and grip length (1/8" x .400)(.188-.250 grip) (for about 75% of my plane... I need a few of smaller diameter and shorter, on the trailing wing edge tubes, and a few longer 1/8" that have alonger grip length (around .360), where I'm joining thicker tubes).

~

Since I'm on an extreme budget, I pretty much have to use what I have. Since I have two 460's and two planes, I'll see what I can do with the 460's for a while. If they don't work out, I'll get hopping on rebuilding the Cuyuna 430.

Around my area (southeastern US), it's a patchwork of about 50% cleared farmer's fields, and 50% forests, viewed from Google Earth.

I plan to make it a point to stay over or within gliding distance of a field as best I can.

The 460's must of worked for somebody once upon a time. One person who was nostalgic about them, was pretty gun ho and offered to buy them both off me.

He told me the 460's didn't use tuned pipes... as a tuned exhaust for it would be way too long... just a 6 inch exhaust pipe. That answered one of my questions.

Is there any way to figure out where I should start with the needle and jetting stuff on these 460's...

If I bought Mukuni or Bings off of ebay for them, how close is the stock that comes in them going to be to "right" for a 460?

Or should I not fret about it too much off the bat, until I've run them a while and then want to fiddle with the jetting to make them run better?

What I need is to find a local motorcross nut who lives and breathes tricking out his two strokes... or become said nut myself. I print out all the real world tips and advice I find on running aircraft 2 strokes and keep it in it's own binder.
 
Last edited:

Armilite

Well-Known Member
Joined
Sep 5, 2011
Messages
3,651
Location
AMES, IA USA
I would look at these New Carbs. Flat Side Carbs are as close as you can get to Fuel Injection.
eBay item number: 262649382095

Chotia 460 Manual
http://ulav8r.com/weed flyers files/Chotia-460_NewManual[1].pdf

From Manual:
===> Never run the engine at full power for more than 45 seconds while on the ground or it may
overheat. Avoid slow air speed climb outs at full throttle when the outside air temperature is
above 85 degrees F. It is best to add 2 – 3 mph to your climb speed on hot days to avoid
overheating the engine and thus seizing it up at this most critical time in your flight.
For optimum performance at take-off and cruise with pilots of average weight, the engine should
develop a minimum of 3400 – 3500 RPM tied down on the ground (static RPM). Heavier pilots
will need 3500 – 3600 RPM and may experience longer take-off runs, more sluggish climbs, and
lower cruise speeds. Lighter pilots may get by with a bit lower static RPM. However, a properly
broken-in engine should turn 3600 RPM on the ground and unload up to 3700 in the air using a 44
x 19 prop (provided)
. It is impossible to over-rev and harm the engine since its structural red line
is 6000 RPM and it is very hard to reach 4000 even in a dive. <====

While I don't see the Spec's of the Chotia 460 I think it was less than 20hp. From From Wikipedia the Chotia Weedhopper seeemed to use more Rotax's 277, 377, 447, account the Chotia 460 was under powered for it. I would seriously looked into maybe bumping up the Compression, and using a Good Tuned Pipe for your Max rpms.

Web Post: Mine swings a 44/18 Prop. this Chiotia 460 single cyl. dual points ign. One set of point set ATDC for hand starting and the second set of points for BTDC spark timing for power production. engine was [email protected] 25 hp however people say it was more like 15hp. It pulls me and a 256lb plane not bad also not as reliable as a modern engine. if someone could setup a solid state ign. might be an opt. With the points and condinser ign.

===> Web Post: Hi. I said i'd get a weight on the chotia 460 i told you about. Chotia 460
Formerly Produced by:
Weedhopper of Utah INC.
1148 Century Drive
P.O. Box 2253
Ogden, UT 84404
(801) 621 3941
(they are no longer located there) Check this site [email protected] groups.com

This company produced the first engine specifically designed for ultralight aircraft. Unlike most engines used on ultralights in 1982 that were designed for other purposes and adapted, the Chotia 460 gives large torque at low rpm. It was designed for long life, reliability and ease of tuning.

Type: Single Cylinder, air-cooled, direct drive, two stroke.

Cylinder:
Bore: 88.00 mm (3.47 in.)
Stroke: 75.00 mm (2.95 in.)
Swept volume: 456 cc (27.85 cu in.)
Schnurle-port design.
4 bolt exhaust flange.

Connecting Rod: Machined bar stock.
Needle bearings at both ends.

Crankshaft: Three ball bearings.
Reversible rotation.
Direct drive.

Induction: Impulse fuel pump.
Bowl-type carburetor.
Fuel-Oil ratio 50:1

Ignition: Four D - sized flashlight batteries giving
24 Hours operation before full-power misfire
(Then giving 4 hours cruise available)
Standard 14 mm spark plug (NGK B6ES) NOTE: If using Radio equipment Get a spark plug that has a resistor in it!!! Like a NGK(b R 6es)

Dimensions: Length 305 mm (12.0 in.)
Width 178 mm ( 7.0 in.)
Height 406 mm (16.0 in.)
Weight (DRY) 14.3 kg(31.5 lbs)
Performance Ratings (S/L):
T-O 18.6 kW (25 HP) at 4700 rpm
Continuos 14.9 kW (20 HP) at 3500 rpm
Prop size 44/18 approx.
=====================================
I don't see the Compression Ratio(CR) it use's, but if you take your Cranking psi and divide by 14.7 that will put you in the Ball Park. Condsider this, a Single Cylinder Simonini 400.5cc engine with 9.5cr, Tuned Pipe, makes 54hp at 6500rpms. Simonini Engines Case and Cylinders are Optimized for Max Air Flow.

Chotia 460 = 456cc, if 90% efficient at 3500rpms = 34hp & 51cfm if Designed and Built right, is possible! Match the Carb CFM to the Engines CFM, and machine the Head for a 10.8 to 11.8cr. 91 Octane is good for Max Cranking 175psi. 175psi/14.7 = 11.9cr. Cylinder & Case Porting can add 10-15% to over all HP! A Tuned Pipe in place of a Muffler can add 35% more HP. If, it's 90% efficient and it makes [email protected] + 15%(Porting) = 23hp, 23hp + 35%(Tuned Pipe) = 31.05hp.

Considering the 1971 Skidoo Blizzard Singles, 246(29hp), 292(31hp), 340(36hp). The 277 was never put in a Blizzard but made 26hp at 6250rpms with a 11.8cr.

Personally, I would sell the Chotia 460's and just buy any Rotax Single, and you would have a better engine. Many of the old Sled Singles go for $50 to $150. You have the 246/247/250, 277, 292, 299/300/302, 318/320, 335/340 to pick from. Some even have CDI or can be converted from Points over to CDI easy.

If you go with the Chotia, I would differently look into using the Engine Ceramic and other Coatings!!!!
 
Top