Volvo GTX racer

[Mark75H]

Corin Huke in the UK found some information for me this week.... A photo of one of the Volvo racers from the 1970's:

[crazy horse]

Sam, How many cyl. did that engine have ? Was it a 100 cid. 2 stroke ?

[F1RACER71]

Konig printed a brochure in 1977 with this info:

UIM Class: OE
Cylinders: 3
Displacement: 840cc
100 HP @ 7000RPM
Bore 77 mm
Stroke 60mm
Gear Ratio 13 : 16
Weight 69kg

[mk30h]

Nice looking engine.
Does Volvo Penta still make/sell engines in Europe? Thought they were called Archemedies or something along those lines. Any connection with the Selva (sp) motors.

[Mark75H]

No, there is no connection with Selva made in Italy.


If I read the Swedish correctly 1979 models of Archimedes and Volvo Penta were sold until 1982.

[Mark75H]

Pretty cool

Link to the movie (http://www.penta.volvo.se/history/lotech/default.asp?strDecade=1970&strYear=-1&strStoryId=&strMovieId=../movies/honken_T1.mov)

[Mark75H]

Nice looking engine.
Does Volvo Penta still make/sell engines in Europe? Thought they were called Archemedies or something along those lines. Any connection with the Selva (sp) motors.

I found this text on the Volvo site:


In 1973, Volvo Penta acquired outboard production from Monark-Crescent and the U-22, Monark and Archimedes became new products in the already extensive Volvo Penta programme. To begin with, sales of these outboard engines were acceptable, but towards the end of the 1970s competition from the Japanese became too fierce, sales started to show a loss, and the production in Uppsala was terminated.

[Per]

It was a real shame that they put down the manufacturing of outboard engines. They were not better or worse than any of the other engines of that era. from what I've been told the Swedish outboards got caught in between when the Japanese and US manufacturers had some kind of price war...
From what I have seen the engines was of different design compared to most other engines. Different but not bad!
I have two 70 hp engines one Archimedes 70 and one Volvo Penta 700 they are supposed to be quite close related to the GTX even tough the engines I have are fishing engines.
If i remember (gold fish memory) I will take a pic of the exploded parts diagram I have for one of mine engines.

I would love to take a peak under the hood of one of those GTX engines. Rumour says that there are one left in Uppsala here in Sweden so it might not be impossible. Of course it's a four hour drive to Uppsala, still it might be worth the effort.

[minto]

The Volvo 600 more or less cleaned up in the old SD class and it's equivalent monhull division (seen in the movie). During the 70's European boat magazines never seemed to be short of Volvo advertisments featuring their racing achievements.

[CALVIN]

Were the volvo engines loopers or directcharge/x-flow

[Mark75H]

Loopers

[Per]

Here's the exploded parts diagram I promised a couple of weeks ago...

Keeping my fingers crossed since this is the first time i upload pics to S & F


http://forums.screamandfly.com/Gallery/showphoto.php/photo/9380/cat/503/limit/recent

[Mark75H]

Thanks Per.

What are parts # 18, 19, 20 and 21 (also numbered 1, 2, 3, & 4)?

[Per]

Thanks Per.

What are parts # 18, 19, 20 and 21 (also numbered 1, 2, 3, & 4)?

Those are the rotary valves, made in some kind of glass fiber reinforced plastic. Anyway they smell really funny when grinded to change the intake duration.
The engine having two carbs have a funny way of distributing the intake charge, the top and bottom cyl with only one rotary valve both have significantly longer intake duration than the middle one that uses two valves.

One small disadvantage with the system is that it depends on small springs to keep the rotary valves pushed against their sealing surface.
They wear out and loose their tension and I suspect that some well needed intake charge is lost that way before the engine picks up the RPM.

[Fast Fred]

how did it hold up with them valves, with them style valves you could super charge and it would actualy do some thing other than make a big hole in your wallet. super charged reed valve is a waste of time. but that would work:cool:

[Mark75H]

Reed valves aren't the problem with supercharging ... exhaust ports being open last are. Reed valves would be superior to rotary valves on a blown 2 stroke if it were not for the exhaust problem.

[CALVIN]

Where are the carbs mounted? On the side or in front?

[Fast Fred]

wait up, on a reed supercharged set up, the reeds never close, the charge pressure never drops, on a natraly asp' reed set up reed closes, piston makes pressure for the charge, the charge hits, charge pressure falls off, intakes close,
exhaust turn into intake just be for it closes. the falling pressure of the charge is the key, all you are doin dif' is stuffin more volume in , every thing else work the same.:cool:

[Mark75H]

You do not have to have the piston and crankcase acting as a transfer pump to force mixture to the transfer ports, simply higher pressure in the transfer passage than in the cylinder (GM's famous Detroit Diesel 2 stroke motors did not use crankcase pumping, only a supercharger). The cylinder and crankcase do not care how the pressure differential comes about. The "charge pressure" does not have to drop, it only has to be higher than the cylinder pressure while the transfer port is open.

Reed valves will not allow backflow from the crankcase to the supercharger. If the supercharger is pushing so hard that the reeds stay open all the time, there is flow and pressure going IN. This in direction will include up the transfer passage to the cylinder. It would take a monsterous supercharger to actually keep the reeds open all the time. If the reeds are kept open by a supercharger the direction of flow is in toward the transfer ports. The flow direction and pumping effect of the crankcase would only be enhanced by a supercharger and reed valves.

If I have 2 jugs connected by a pipe and a big fan blowing into the first jug and an opening to the atmosphere on the second jug - air will travel from the fan to the first jug, to the pipe, to the second jug as long as the pressure is higher on the fan side. If I put a check valve between the fan and jug 1 flow still goes jug 1, pipe, jug 2. If I squeeze jug 1 very hard, the check valve may close, but the flow still continues the same direction to jug 2. If I squeeze jug 1 just a little the check valve stays open - the flow still goes: fan, jug 1, pipe, jug 2; no interruption of flow to jug 2. If I put a pump in jug 1 the flow still stays. Jug 1 was the crankcase, jug 2 was the cylinder, the pipe is the transfer passage between them.

At the cylinder you have jug 2 with 2 holes ... you blow in one while the other is open ... all your breath just goes out the open hole as long as you stop blowing in the blow in hole before closing the open hole. The holes in jug 2 are the cylinder ports; the "blow in" hole is the transfer port, the "open" hole is the exhaust port. On a 2 stroke the exhaust port must open first to let the explosion exit to the exhaust pipe. The unfortunate construction of 2 stroke motors requires symetry in open time of the ports: the exhaust port also closes last (always). If the transfer port opened first or at the same time, the explosion would travel into the transfer passage and ignite the incoming charge. Reeds are not the issue, port symetry nullifies any pressure increase from supercharging, intake valving type has little effect on this phenomenon.


Intake valving type & 2 stroke supercharging

In a very limted way intake valving will affect trying to supercharge a 2 stroke motor. The worst type to use would be old fashioned 3rd (piston intake) porting. 3rd porting would bring back the symetry issue: the port will open and close at the same time relative to top dead center, x degrees before and x degrees after. Give the port a good opening time, and it will have a poor closing time ... at all rpm. In the middle would be rotary valve intake. Since you can't change the time on a rotary valve while the motor is running, you must choose whether to time the opening and closing for high rpm performance or lower rpm performance. Next would be reeds. Self adjusting for time and flow, just about ideal for a spark ignition 2 stroke on a boat ... the only drawback is that they operate by a slight pressure drop: you have to have higher pressure on the intake side and lower on the outlet side for them to open. On a supercharged 2 stroke the ideal intake valve would be the supercharger itself, no valve, no restriction, no flow timing, just flow into the crankcase.

[Mark75H]

exhaust turn into intake just be for it closes. Not near enough effect from adjacent cylinder tuning or expansion chamber reversion to overcome what is lost before the change

[Per]

Where are the carbs mounted? On the side or in front?

The carbs are side mounted, looking at the parts diagram they are held in place by the studs marked #33

The "square" castings that they are mounted to is actually a kind of chamber that connects the carbs and let the 3 cyl share both carbs. (Did that make any sense? :rolleyes: )

Will take some pics of the engine, as usual it might take a while...

[SD489]

Both engines are the same.
I have an old photocpyed Spare parts list on these engines.
His quality is under today average, but inthose times....
The engine is the old 600 cc tuned up, the basic engine blok
of the very popular Archimedes Penta - Crescent 55O of the
7o´s, but tuned up for racing in SD Class, equiped with an
Konig gear.
I have one of these Konig lower gear unit, with his particular
bronze popellers.
I will like to share info about this engine,
Just for your pleasure I send a picture of my Canali Jerry, last year,
a full "speed" in south Mallorca Island, with one of these 600 cc
engines.
Regards
Juanhttp://motonautica

[Mark75H]

Thanks, Juan. I like it.

How long is that boat?

[SD489]

Hi Mark 75,
The boat is 13 feet long, about 4,70 meters. Is made in plywood, in 1971
aprox by Gianni Canali in Como, North Italy, it has a very steep v hull.
I used to drive it in the 70´s with an Archimedes Penta 550 X, factory tuned. In the picture is with an standart engine, but I magaged to get a original Crescent Tornado (orange colour), and my next proyect is to place the
Tornado instead of this one, to feel the real racing thrill.
These engines delivered about 60 HP and his weight is aprox 60 kilos =132
lb., not bad.
There is a picture of boat in profile.http://0029.1.JPG
Regards to eveybody,..
Juan

[SD489]

http://MotonauticThe picturehttp://0029.1.JPG

[Mark75H]

it has a very steep v hull.

Very much like a Sonny Levi style boat

Thanks for the pictures and information