VW Beetle engine 1/5 scale

[Arild]

Yes, I kow, I updated my "A" to a Ferrari picture,, I bought that 10 years ago as a damaged car. Spend a lot of money on engine, but did the most of the work I did by my self.... I tried to make a replika of that engine. Ive'made the crank and one sylinder head, but gave up the block, so over to the VW!

And now there is snowing! Already 10cm of wet snow. Me dont like - I like Thailand!!

 

[petertha]

I was reading about carburator not so long ago on this forum. "How large (or small) it should be". Where do I found it? -My engine is about 3,6ccm x 4. Does it matter how many cylinder there is, or are we simply looking at one cylinder when we talk about the size of the opening?

Your VW build is fantastic! I used to have a 1969 Karman Ghia. Rebuilt the engine from 1500 to 2000cc displacement. Not a good car for a starving college student with little money, especially cold Canadian winters HaHa. But I do have a few fond memories.

I'm interested in your initial design work flow. Did you use factory engine drawings for background layer reference & developed the CAD model off that?

I posted a few carburetor charts on the forum, here are some links. I suspect there are many variables involved, but one of the stronger initial estimate correlations seems to be displacement to throat size assuming typical RPM & cam timing. Please note some of this information pertains to methanol fuel vs. gasoline (methanol = larger orifice) so I tried to label that distinction. I also wondered about how much to increase carb size based on multiple cylinders when I built my radial. The usual suggestion is add proportionate to combined intake period of multiple cylinders. But maybe an overview comment from my own reading - seems like many builders initially estimate a bit large based on scale factor & end up with something a bit smaller in real life running. So all I would say is - integrate a design plan where you can swap different size carbs with little effort, or ability to modify the intake throat diameter. Look forward to more build pictures when you post!

https://www.homemodelenginemachinis...-917-flat-12-engine.32972/page-16#post-374923



https://www.homemodelenginemachinist.com/search/2133740/?q=carb+sizing&c[users]=petertha&o=relevance



https://www.homemodelenginemachinist.com/threads/2-stroke-twin-wont-start.26098/#post-285862

 

[Arild]

Your VW build is fantastic! I used to have a 1969 Karman Ghia. Rebuilt the engine from 1500 to 2000cc displacement. Not a good car for a starving college student with little money, especially cold Canadian winters HaHa. But I do have a few fond memories.

I'm interested in your initial design work flow. Did you use factory engine drawings for background layer reference & developed the CAD model off that?

I posted a few carburetor charts on the forum, here are some links. I suspect there are many variables involved, but one of the stronger initial estimate correlations seems to be displacement to throat size assuming typical RPM & cam timing. Please note some of this information pertains to methanol fuel vs. gasoline (methanol = larger orifice) so I tried to label that distinction. I also wondered about how much to increase carb size based on multiple cylinders when I built my radial. The usual suggestion is add proportionate to combined intake period of multiple cylinders. But maybe an overview comment from my own reading - seems like many builders initially estimate a bit large based on scale factor & end up with something a bit smaller in real life running. So all I would say is - integrate a design plan where you can swap different size carbs with little effort, or ability to modify the intake throat diameter. Look forward to more build pictures when you post!

https://www.homemodelenginemachinis...-917-flat-12-engine.32972/page-16#post-374923



https://www.homemodelenginemachinist.com/search/2133740/?q=carb+sizing&c[users]=petertha&o=relevance



https://www.homemodelenginemachinist.com/threads/2-stroke-twin-wont-start.26098/#post-285862

I found an drawing at the open source "onshape" community. But I had to modify it, as it was not good enough for an model engine. I've already started to a make a 904 to fit that engine. If I don't succseed with my engine, I will make that car electric! What a negative tought!! Karman Ghia was also on my list!

 

[Wp356]

I am enjoying your postings. Pleased you mentioned the Karmann as a possibility. I like the Karmann styling as much as a 356. I used to have a '69 Ghia in appropriate "Texas Yellow"

 

[Jan Dressler]

I've already started to a make a 904 to fit that engine.

Very nice Beetle engine, I am watching and learning...

Regarding the 904, the original one had the Fuhrmann quad overhead cam engine. No pushrods in there... Shafts and bevel gears, lots of them. A nightmare to set valve timing.

 

[Tom-AMS]

Thanks for the useful information. In my cam design, the cam lift 2.3mm, so according to the original that is to much (should have been 7.65/5 =1.5mm), but I guess it won't hurt? However a scale down doesnt neccessary have to - or can be the same as volume decrease by 125 and not 5 (the engine I build is scale 1:5, and the volume is then 125 times less). likewice my valves has a 2mm stem (not 1.6 as in scale), valves face diameter is 7 and 8mm, so that is pretty close to the original!
I'll adjust my cam degree according to your description!

as long as the valve clears the piston*, and the valve spring coils don't bind, the higher lift should be ok. check for valve to piston clearance.

 

[Tom-AMS]

Very nice Beetle engine, I am watching and learning...

Regarding the 904, the original one had the Fuhrmann quad overhead cam engine. No pushrods in there... Shafts and bevel gears, lots of them. A nightmare to set valve timing.

we often refer to this engine as the 4-Cammer. Here's pics of some of the work I've done in the past couple of yrs on the full size Type 547 engine for a 550 Spyder. I've been involve with casting & machining replacement cylinders for them too ( four pics are raw castings; we chose to make individual heads (like 911) and then a cam support casting. I rebuilt & rebalanced the cooling fan, last to pics of of a used engine my customer was trying to buy.) It takes me about 9 hours to assemble the heads, cams and drive shafts, fit spacers to set gear lash & endplay, etc.

 

[GreenTwin]

Tom-
You need to start a separate thread for your VW engine work.
Those are some fantastic mods to a VW engine, and this work deserves its own thread.
What a nice and clever piece of work !
.

 

[Arild]

Aligning up the engine body and mill out the slot for camshaft bearing.. Then make a closed end brass bearing at the flywheel end.
The other end bearing will be more difficult, as it is off-center due to the oilpump (I'll not have a oilpump, and see how it goes with just "splash lubrication).
I used brass as bearing on this one as a mistake, all the other (and gears) are in bronze. But I read about it and brass on steel are pretty good bearing too!
However, progress is a bit slow for the moment. It's soon Christmas and my wife complain that I don't do enough housework and preparations!

 

[Arild]

I can't help with locating the previous post about carburetors, - however, I can say that the VW Solex 30-PICT-1 carburetor used on a 1500 cc engine (83mm bore X 69mm stroke) has a 24mm venturi. Stock rocker arms have 1.1:1 lift ratio, stock intake valves were 35.5mm dia. with 8mm stem; exh valve 32mm with 8mm stem. Stock cam lift ~7.65mm int / ~7.24mm exh. Cam valve timing (@ 0.050" lift) is Int. open 1° BTDC / close 30° ABDC. Exh open 36° BBDC / close 4° BTDC. Cam lobes are tapered to cause cam follower (aka lifter) to rotate. Lifters are "domed", not flat, with ~1400mm radius. Lifter "face" diameters varied over the years, from 28mm to 31mm. The most common used in the 1500 and 1600 cc engines were 29mm and 30mm. The smaller face diameter was used to reduce effective cam duration, increase dynamic compression, and increase low RPM torque. I have 60+ years reanufacturing VW air-coled engines, plus building many hi-performance versions. On our Superflow 600 flow bench a stock VW single port head (casting # 311-101-373A; p/n 311-101-353A) flows ~96 CFM at 8.4 mm valve lift at 28" H2O. A stock Dual port head (casting # 043-101-375A; p/n 043-101-355A) flows ~102 CFM, with same lift and 28" H2O. With a prpoer valve job and some port work, we can get stock DP heads to flow 250 CFM. You may be able to use the above info to "scale" your model carburetor.
The pushrods and pushrod tubes (with corrugated flex ends) angle upward toward the cyl. head, and also angle front to rear. The front to rear angle varies for each pushrod and tube is not equal. It varies progressively from 0° for one pushrod, ~1.5° for the 2nd pushrod, ~4° for the 3rd pushrod, and ~5.5° for the 4th pushrod.
Looking forward to seeing more of your fantastic VW engine build.

I made up a drawing to better understand the opening and closing. When I transfer this to the cam, I divide the degree by 2. The relation between intake and exhaust is the, 17.25deg (+180/2) at top of the lobes. (107degree). Both intakes lobes are 90(180)degree apart, and the same for exhaust lobes. Am I correct? I 3D printed the cam and compared with pictures of the original. It seems correct for me.. Last picture is a jig to be used when milling. I'll mill down roughly and then use a hand file to make it smooth.