Cox Engines Forum
You are not logged in! Please login or register! Guests are limited to posting in the "General Questions (Guest Posting Allowed)" section only. Becoming a member is fast, easy and FREE!


Back Plate Hole size for Venturi (behind screen) Babe_b10
Back Plate Hole size for Venturi (behind screen) Pixel

Log in

I forgot my password

Search
 
 

Display results as :
 


Rechercher Advanced Search

Latest topics
» Filling cotton inside of muffler?
by Levent Suberk Today at 3:26 am

» Minnie Mambo Rescue
by GallopingGhostler Today at 1:40 am

» The Stork
by KariFS Today at 12:43 am

» Dope free build
by OhBee Today at 12:31 am

» Jerobee Alfa T33 Can Am.... It’s all mine!!!
by davidll1984 Yesterday at 11:19 pm

» Wanted: Decals Thunderbolt
by dckrsn Yesterday at 11:11 pm

» Tarno carb operation
by dckrsn Yesterday at 10:35 pm

» question: gas powered cox or other 1/2a engines using the OS G5 plug
by davidll1984 Yesterday at 10:16 pm

» Free Flight Modelling
by NEW222 Yesterday at 7:35 pm

» Model Locomotive stuff
by rsv1cox Yesterday at 1:43 pm

» **Black Lynx Engine Giveaway** Cox Engine of the Month (2020)
by MauricioB Yesterday at 10:16 am

» TD 09 Ducted Fan
by getback Yesterday at 8:39 am

Cox Engine of The Month
January-2021
Jason_WI's

"Bucket-O-Parts Cox TD .15 Special"



PAST WINNERS

CEF Traveling Engine

Win This Engine!
Forum Store
CEF Ear Savers
Gallery


Back Plate Hole size for Venturi (behind screen) Empty

Back Plate Hole size for Venturi (behind screen)

Go down

Back Plate Hole size for Venturi (behind screen) Empty Back Plate Hole size for Venturi (behind screen)

Post  sosam117 on Thu May 14, 2020 10:56 am

While cleaning up my Texaco engines I noticed the Venturi hole sizes were different.
The original "Texaco .049" engine with the black back plate has a venturi hole size of .086"
The original "Texaco .049 Jr." engine with the gray back plate has a venturi hole size of .063"
So, I looked at my old Thimble Drone .049 with the metal back plate and the venturi size is .063"
I modified the Texaco .049 back plate with a 3/32 o.d. aluminum tubing 1/16 long
and press it into the .086 diameter venturi hole.
The i.d. on the aluminum tubing is 1/16 dia.

Why were the larger 8cc Texaco engines have the larger .086" holes on the venturi?
Is that why the Texaco Jr. had the "gray" back plates to tell the different venturi size?
And now I know why when I flew in the SAM Texaco event, some of the other contestants had the old metal back plates.
They got longer runs than what I was getting.
I tried to get longer runs by removing some of the plastic inside the back plate but that was still not enough.
You can see the removed plastic in the photos.

I'm guessing the larger venturi hole was for the Black Widow and other hotter engines?
What are your ideas?

Original Cox Texaco .049 back plate with a .086" diameter venturi --- plastic removed inside for more fuel.
Back Plate Hole size for Venturi (behind screen) Origin10

Original Cox Texaco Jr. .049 back plate with a .063" diameter venturi.
Back Plate Hole size for Venturi (behind screen) New_ai10

Original Cox Texaco .049 back plate modified with a 3/32 o.d. x 1/16 i.d. x 1/16 long aluminum tubing.
Back Plate Hole size for Venturi (behind screen) Mod_ai10
sosam117
sosam117
Gold Member
Gold Member

Posts : 281
Join date : 2016-03-23
Location : Suburb of Chicago, Illinois

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  aspeed on Thu May 14, 2020 12:09 pm

As long as you are allowed to put inserts in, you could go even smaller than .062" Just make it the right size to lift the plane up steady.
aspeed
aspeed
Platinum Member
Platinum Member

Posts : 533
Join date : 2013-01-18
Location : Leamington Ont. Can.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  sosam117 on Thu May 14, 2020 10:35 pm

aspeed wrote:As long as you are allowed to put inserts in, you could go even smaller than .062"  Just make it the right size to lift the plane up steady.

The 3/32 aluminum tubing is a nice press fit into the larger hole.
So the I.D. of the tubing automaticly is 1/16 of an inch.
Only way it would work out is try to find thick walled tubing to reduce the I.D.
Haven't found any thick walled aluminum tubing?
sosam117
sosam117
Gold Member
Gold Member

Posts : 281
Join date : 2016-03-23
Location : Suburb of Chicago, Illinois

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  aspeed on Fri May 15, 2020 9:25 am

I guess I am spoiled with a lathe. A piece of welding rod with an appropriate size hole would work. It would need to be fairly centred, or solder up brass tube and drill it out.
aspeed
aspeed
Platinum Member
Platinum Member

Posts : 533
Join date : 2013-01-18
Location : Leamington Ont. Can.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  Basswood on Fri May 15, 2020 1:21 pm

Sosam 117
My thinking is when you pressed in the aluminum tubing you probably almost took away as much volume as you created removing the plastic in the fuel tank.
Basswood
Basswood
Basswood
Silver Member
Silver Member

Posts : 97
Join date : 2020-02-19
Age : 64
Location : Phoenix, Az.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  aspeed on Fri May 15, 2020 8:06 pm

Basswood wrote:Sosam 117
My thinking is when you pressed in the aluminum tubing you probably almost took away as much volume as you created removing the plastic in the fuel tank.
Basswood
I think it is in a separate passage before the tank, so it would be a plus still. You can also turn away some of the centre part, as it tapers down to about 3/32" so you could get a few more drops of running time.
aspeed
aspeed
Platinum Member
Platinum Member

Posts : 533
Join date : 2013-01-18
Location : Leamington Ont. Can.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  Basswood on Sat May 16, 2020 12:36 am

[quote="sosam117"]While cleaning up my Texaco engines I noticed the Venturi hole sizes were different.
The original "Texaco .049" engine with the black back plate has a venturi hole size of .086"
The original "Texaco .049 Jr." engine with the gray back plate has a venturi hole size of .063"
So, I looked at my old Thimble Drone .049 with the metal back plate and the venturi size is .063"
I modified the Texaco .049 back plate with a 3/32 o.d. aluminum tubing 1/16 long
and press it into the .086 diameter venturi hole.
The i.d. on the aluminum tubing is 1/16 dia.

Why were the larger 8cc Texaco engines have the larger .086" holes on the venturi?
Is that why the Texaco Jr. had the "gray" back plates to tell the different venturi size?
And now I know why when I flew in the SAM Texaco event, some of the other contestants had the old metal back plates.
They got longer runs than what I was getting.
I tried to get longer runs by removing some of the plastic inside the back plate but that was still not enough.
You can see the removed plastic in the photos.

I'm guessing the larger venturi hole was for the Black Widow and other hotter engines?
What are your ideas?

Original Cox Texaco .049 back plate with a .086" diameter venturi --- plastic removed inside for more fuel.
Back Plate Hole size for Venturi (behind screen) Origin10



It looks to me like the aluminum fill stem is down inside the fuel tanks cavity. It would have to be to fill the tank.anything you put down inside that cavity (fuel tank)is going to reduce its capacity.
So if you pull that aluminum stem out to the edge of the back plate it will increase the volume in the tank.just like cutting out the plastic.try to find a glue that's fuel safe and glue it.
Now what I'm trying to understand is. are you trying to reduce the engines fuel consumption by restricting the air flow of the fill tube/stem?
otherwise use .014 tubing rather .035 or .045 thick wall tubing and you may get a drop or two in the tank fill tubing/stem.If you used an end mill you could remove more plastic in the back plate also.but it looks like you did a pretty good job of that already.
Just my two cents.
Basswood
Basswood
Basswood
Silver Member
Silver Member

Posts : 97
Join date : 2020-02-19
Age : 64
Location : Phoenix, Az.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  getback on Sat May 16, 2020 5:35 am

getback
getback
Top Poster
Top Poster

2019 Supporter

2020 Supporter

Posts : 7452
Join date : 2013-01-18
Age : 63
Location : julian , NC

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  Basswood on Sun May 17, 2020 12:08 pm

Thanks for the link getback. lots of great info in it. keep in mind I'm looking at this strictly from an engineering point of view only.
you could also make tiny thin washers out soda pop can with different size drilled center holes to slip between and venturi stem seal and the fuel tank back plate.
Basswood
Basswood
Basswood
Silver Member
Silver Member

Posts : 97
Join date : 2020-02-19
Age : 64
Location : Phoenix, Az.

Back to top Go down

Back Plate Hole size for Venturi (behind screen) Empty Re: Back Plate Hole size for Venturi (behind screen)

Post  Sponsored content


Sponsored content


Back to top Go down

Back to top


 
Permissions in this forum:
You cannot reply to topics in this forum