single vs twin

[mikey]

Are the singles more reliable than the twins?

[diesel guy]

Mikey,

Everyone has their own option on that subject. My option for what its worth is, the gear and cam design are the limiting factor on the twins reliability and overall durability otherwise they seem equal. For me a single equipped with Georges bronze idler gear has half the shock load from operating the lifters and fuel pump and provides a sense of confidence the twins can’t  match.

Diesel Guy

[Halfnuts]

On the other hand, the twin will be mechanically better balanced than the single and instead of having one big thundering power stroke, it will have two smaller ones spaced 180 degrees apart. 

Halfnuts

[cujet]

There are some built in problems with the twins that may factor in. One big issue is the total lack of lubrication on the injector pump lobe and bearing (farthest from cam idler gear). Another issue in some engines may be the extra stress placed on the idler gear by a camshaft doing twice the work as a single. Certainly the balance issue is not solved by the twin as there is a huge rocking couple that is very difficult to balance out. One thing some forget about is that the single is able to run with a low pressure in the crankcase due to the reed valve. The twin cannot do this. The result is that twins may leak more, and quite often engines with low pressure in the crankcase are slightly more efficient.

On the other hand, the loss or lack of power on one cylinder does not result in total loss of power. The twins will still run on one cylinder. So, troubleshooting may be slightly easier.

My overall guess is that the single is more reliable.

Chris

[snail]

     My twin certainly does leak! I've searched the forum, but nobody seems to have suggested  any way of reducing the pressure in the crankcase. I'm not (even slightly!) inclined to try a 360 degree crank so what else is there? Vacuum pumps seem a bit extreme but there must be some simple idea that I haven't thought of ( like the brilliant crankcase door oil filter).
     

Cheers

Brian

[WWIProps]

Brian,

Try replacing the reed valve with a spring loaded check valve.  I used a flange from a taco pump and a 1" check valve vented to the outside.  The spring tension out of the box was a little strong so I dissassembeld, cut the spring in half and put it back together.  Works like a champ.  I have no puddles under my engine.

Scott

[SHIPCHIEF]

We went thru a bunch of posts a while back regarding crankcase pressure and venting. WWIprops was a contributor then, so his reply now is top value.
Cujet is totaly correct about twin's lack of lubrication on the injector pump cam lobe farthest away from the cam gear. The cavity has a oil drain hole back to the sump, but the IP cam and roller tappet are lubricated by the minimal throw off from the camshaft case bushing.
I drilled the casting that supports the injector pump assembly, and tapped / installed a 1/4 pipe -hose fitting with a little piece of brake tubing brazed in. The tube aims right where the cam and roller tappet contact. I take alittle pressure oil from the pump to lube this. I think the oil pump has plenty of capacity, because the oil distribution manifold (above the crankcase door) has pads for five oil discharge tubes. My engine only uses three (one for each main bearing) the other two were originally used by Lister to fill oil troughs for the con rod dippers. On Rocketboys Lister pages you can see a picture in his crankcase with two tubes going straight down. These must be unused as trough fillers, because his sump does not appear to have troughs. It does unload the oil pump though. I wonder if the Ashwamegh cam gear failures are caused by oil pump overload, because these two tubes are not drilled / installed, so the oil pump has 40% less cross section of discharge area?
Scott E

[binnie]

Scott,
You have to be a plumber, mechanic, electrician & genius to work on one of these machines. I am none of the above. Do you have some picts you could post of your modifications. It would be nice to see exactly what you are discribing. I think the Taco pump is for water circulation on a boiler system..but would be nice to see what you did. thanks.

[WWIProps]

Binnie,

I have posted a photo on coppermine.  It is a shame that my picture had to come up next to hotater's masterpiece. 

Keep in mind I said that mine did not leak, I did not say that it was clean!

Good luck.

Scott

[binnie]

Thanks Scott
for the picture...worth 1,000 words! I appreciate. From what I understand in my limited grasp of the situation, is that this little gadget you have installed inline with the 1/2 spring mod. in it...opens when the pressure peaks, and lets off excess pressure, vented to the outside, evening out the pressure peaks & avoiding any leaks. Hit me if I'm wrong. (thanks for your patience).

[WWIProps]

Binnie,

You are correct.  It acts justlike the reed valve on the engine right now.

Scott