Author Topic: DES 8/1 generator build  (Read 40714 times)

32 coupe

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Re: DES 8/1 generator build
« Reply #60 on: October 22, 2016, 11:41:07 PM »
 I am unable to tell from the pics but on 1 of my engines the valve guides were reversed !
The exhaust guide will have a recessed area.

Gary
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gusbratz

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Re: DES 8/1 generator build
« Reply #61 on: October 22, 2016, 11:49:27 PM »
Hmm i didn't even look at that, guess i will have to take it back apart.

38ac

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Re: DES 8/1 generator build
« Reply #62 on: October 24, 2016, 01:46:26 PM »
I never liked the way India does the valve seats and prior to being tooled up to install hardened seats I would custom dress a stone so as to (slightly) lay the top of the pocket/seat away from the valve and also used a 60 degree stone to get rid of the bottom thus leaving a prim and proper narrow seat at the correct location on the valve. While the wide seats will function they cause problems long term with carbon holding the valve up and this leakage. This doesnt show up running, only when you try to start the engine cold, especially after sitting a spell. Be mindful of the valve recession spec, its important.

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 I have also noted switched guides on a couple singles. The #1 head for a twin is a mirror of #2, same head with guides switched,
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EdDee

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Re: DES 8/1 generator build
« Reply #63 on: October 24, 2016, 02:54:38 PM »
Hi GB,

Watch out for the oil filter being inverted as there are a few reasons I would cite .... Filling and priming the filter prior to initial installation is problematic.... Airlocks would become a problem and could stuff you around... Personally, I would rather go with an inverted U type bracket and turn the filter over - Another reason for correct mounting is to allow for water or moisture to be trapped in the bottom of the filter - As it is currently mounted, you will probably reintroduce any water picked up in solution straight back into the sump.

Just my thoughts....

Cheers
Ed

Edit: Something was nagging me...Guys, shoot me down or confirm my thoughts...

The filter you are using probably has a bypass relief spring in it - as soon as the filter clogs, the element can ride away from the seal area(which is normally on top) and allow oil to flow past the internal sealing surface to the outlet of the filter housing. If you have any debris(read that as crap) that has settled at or around this bypass seal area after a few hours/days/weeks of running, will have an express route to your bearings if the bypass feature on the filter activates through being clogged(most likely) or heavy pulsing from the pump when the oil is thick and cold... in short..... DON'T RUN IT AS IT STANDS!!
« Last Edit: October 24, 2016, 05:34:22 PM by EdDee »
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gusbratz

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Re: DES 8/1 generator build
« Reply #64 on: October 25, 2016, 10:15:56 AM »
Balancing the 8/1 engine.
I feel like I am coming a bit late to the party. While researching this I came across a lot of posts, older posts so maybe I missed the big surge when these engines started arriving but I will post my experience anyway. I first started trying to learn about balancing. I read posts here, post on single cyl motorcycle  engines, big block Chevy’s, racing lawnmowers with single cyl kohlers. I learned how you balance 50% of the reciprocating mass and 100% of the rotating mass. Any more than 50 will turn a hopper into a slider. But in real life some v twins and motorcycles are going up to 70 or 80 and really smoothing out. I learned that a single cyl engine will always be a bit of a thumper. Even fitted with balancing shafts. But I felt like something was missing, most of what I read was talking about counterweighted crank shafts. Weight right on the crank. Not big flywheels. I remember learning in school about how if you taped a penny to a 48” steam turbine blade the high rpm and the distance from center are like astronomical. The weight of a penny is over 2 tons of force on the turbine blades. Then I came across this equation in a model steam engine forum.
“I found a formula in an old public domain book, as follows for calculating the counterbalance weight(s) for steam engines, as follows:

Equation for minimizing engine vibration:

W1 = [K*(W2+W3)*r] / X

where:

W1 = weight of the counterweight (lbs.)
W2 = weight of the crank webs outside of the main shaft and crank pin (lbs.)
W3 = weight of reciprocating parts (piston, piston rod, crosshead, one half the weight of the connecting rod) (lbs.)

X = distance of center of mass of counterweight from center of the crankshaft (inches)

K = constant (use 0.67 for minimum vibration at right angles to the engine centerline, use 0.75 for minimum vibration at crank dead center)

r = distance from center of crankshaft to center of crank pin (inches)

Generally, vertical engines should tend toward using the 0.67 value for "k", and horizontal engines should tend towards using the 0.75 value for "k".

So I took some measurements on my des 8/1:
Aluminum Piston, rings, piston pin and cir clips= 4pounds 7.30z
Entire rod with bushing and bearing 8pounds 12.2 oz.
Bushing end 3pounds 20z
Bearing end 6pounds 3oz
Estimated weight of crankpin based on 2.5” diameter and 5.5” length 7.65 pounds
Bore 4.49” stroke 5.49”
Then remembering to divide the bore by 2 and converting all the oz. into decimals I crunched the numbers in the equation and came up with the following recommended counterweight on 24” flywheel.
W1= .67(7.65+8.837)2.745/12”
W1=2.455 pounds.

So feeling like I had a starting point I moved from what my coworkers call “theory and bullshit” and started on the flywheels. Using the forklift forks with a strip of ¼” key stock on the and an old 2” pin from a backhoe bucket I proceeded to balance as can be found here and on you tube. Not the most accurate rig but with a bucket and string and kitchen scale I came up with the following initial numbers
Front flywheel:  total weight 137#, key on bottom when on rack but 1 degree to left of center, counterweight 2.35pounds
Back flywheel: total weight 136.5#, key on bottom when on rack 1 degree to right. Counterweight 2.4437 pounds.
It was neat to see those numbers match up so close to my calculated value. I assume that some engineer in India calculated out the counterweight and designed it into the casting or it was there by luck when they copied the original.
From there I started with the lighter back wheel and instead of drilling holes I used a grinder. Given the shitty look of the cutouts it was no hardship. I cleaned up the insides of triangular holes until it hung straight. Then I took a measurement with the bucket and found the new counter weight was 2.506#. I then proceeded to make the heavy front wheel match the back.
Granted I have spent many hours welding and fabricating but I found it surprisingly easy to remove a pound with a grinder once you start. As soon as you touch it and the paint and putty blows away the natural instinct to contour it, smooth it and grind away the casting sand takes over. It worked out real nice in lowering the weight of the heavier front wheel. I only removed material from the side I needed to get it to hang straight. This both lowered the overall weight of the wheel, corrected the tilt as well as giving the counterweight more of an effect on the wheel. Essentially making it heavier to match the rear wheel.

38ac

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Re: DES 8/1 generator build
« Reply #65 on: October 25, 2016, 02:08:49 PM »
I have run 4 of the DES 8/1s through the shop and all of them had the total offset weight pretty close to right but weight was not in the correct relationship to the crank throw due to the key ways not being cut in the right place. That is every bit as important as getting the weight right.   The 50% number is going to be too low on any single cylinder engine I think unless it has a very light weight piston and rod.  I measured and calculated a very smooth running 6/1 Lister a few years ago but all of that has left me now, I think that I posted some of the information here on the forum.
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BruceM

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Re: DES 8/1 generator build
« Reply #66 on: October 25, 2016, 03:35:10 PM »
Once you have adjusted counterweight locations to match the key and matched them in total counterweight per 38ACs method, it is trivial to fine tune the total counterbalance.  If it moves fore and aft, decrease counterweight.  If it hops, increase counterweight.  Increments of 4 oz on each flywheel are useful. 

I've used the Mr X method in the past, and it does work, but 38ACs method is much faster and easier.


gusbratz

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Re: DES 8/1 generator build
« Reply #67 on: October 25, 2016, 06:40:14 PM »
so how close to the right position is good enough? i got 1 side perfect and the other side is like 1 degree off from being at the bottom. is that close enough?

38ac

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Re: DES 8/1 generator build
« Reply #68 on: October 26, 2016, 12:20:34 AM »
In my shop that would be called good ;)
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gusbratz

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Re: DES 8/1 generator build
« Reply #69 on: October 26, 2016, 09:55:36 PM »
got the new parts from DES. after some shimming and head scratching i started to install them. I am coming up with a bump clearance of .075 back side .085 front (gov side) of piston. i leveled the top of the  frame with a machinist level before i grouted it. now  with a cyl on the frame when i place a level on the cyl top it now it shows the back higher than the front. a tool makers level against the side of the cyl shows the top of the cyl  being off square to the bore. i am inclined to run it like this because i figure the piston is going up and down straight it should just be the head off level by .010. perhaps i should try my other cyl and see how it looks. (the one with the pin hole) i am just feeling lazy and not wanting to fight the piston rings into the cyl again. any thoughts?  

mikenash

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Re: DES 8/1 generator build
« Reply #70 on: October 26, 2016, 10:08:00 PM »
FWIW I would say if the crank is perpendicular to the bore and the rod is parallel to the bore it doesn't matter if the head is "on an angle"  No lateral loads on the bore/piston.  Just an idiot's viewpoint

BruceM

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Re: DES 8/1 generator build
« Reply #71 on: October 26, 2016, 11:20:59 PM »
How much (thinkness) gasket under the cylinder? If it's 25 mils or less you need that cylinder trimmed anyway.
Having the head true to the bore is not critical, I think, but bump clearance sure is.  I had to have my older Metro cylinder cut down more than yours.




38ac

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Re: DES 8/1 generator build
« Reply #72 on: October 27, 2016, 02:20:15 AM »
The bottom of the  cylinder block needs to be square to the bore. The top is not as  critical and 010 across the top means  nothing operationally. Squish will vary side to side for a dozen reasons only two of which should be corrected, the others should be ignored and the squish averaged which in your case puts you right at the top end of the spec. The engine will sart and run fine with 080 bump unless the valves are burried in the head. If you want to reduce the bump and don't have the thinnest gasket under the cylinder then install one. If so remove the gasket and replace it with a bead of silicone sealer.  You of course can have the cylinder machined if you desire.
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gusbratz

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Re: DES 8/1 generator build
« Reply #73 on: October 27, 2016, 02:45:43 AM »
i put one .032 gasket under the cyl. the head gasket is .050 the clearance is right where i want (.075-.080 for aluminum piston). I have a 16" lathe and i think i could chuck the cyl in my4 jaw chuck do runout off the inside and take a faceing cut.

BruceM

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Re: DES 8/1 generator build
« Reply #74 on: October 27, 2016, 04:34:58 AM »
Sorry, forgot the bump is bigger for the aluminum 8/1.  Over .530" on my neighbors propane 8/1 conversion so I forgot.