Simplicity Broadmoor R/S Project

I did think about running the steering below the engine to a right angle box and then maybe have a universal up near the wheel to tip it back a bit. I do have two right angle boxes from the mower deck of a 67 sears custom but they are a bit heavy. Over the engine might be tough yeah, the main issue I think would be the front top edge of the engine. Especially if the engine is shoved right up front, that could be a problem.

The tapered shaft on the 633 is only on the input shaft, so that shouldn't be a bit problem. The axles are where I'll have some sort of hub for the sprocket. But anyway I think you can get tapered hubs for things. I heard they are sort of a universal angle but I don't know, I haven't checked.

I also did think about making the arms longer (Or even crossing over themselves as in a twin I beam front suspension) Upper and lower arms would definitely be the nicer option, so we'll see as things progress.

I like the twin I beam idea ! i've been thinking of something like that. I'll let you prefect it and i'll steal your design lol. I could use some suspension that solid ride is a work out at times and kills the old back !

The old wishbone/mono link setup on the adventure edition works really good and it's a simple design. But I think it's a bit heavier than it needs to be for this project and also I think harder to get the machine lowered down as much. I want to try keeping the bottom fairly flat on this build if I can. The independent suspension might be more responsive for higher speeds too. I was thinking I could use upper and lower control arms and maybe only use the golf cart spindle itself with heim joints on top and bottom. I wouldn't end up using any of the golf cart axle but that might work out good. I just need to see how much space is in the golf cart rims for that. If needed I could even narrow down the spindle to make it fit.

Simplicity Adventure Edition front axle when painted.

Draining the oil from a couple of 633's. Both had some water in them from being outside. The blue one had the most. But both turn easy and shift ok. Maybe they aren't so bad inside. The bare aluminum one is one of the newer splined axle types with the shifter that can't spin. I was wondering if the shifters or axles are interchangeable between cases. I would think they probably are, but we'll see. I'll probably need the older single keyway type axle for the RS so I can mount a chain sprocket on it. The shifter location might not be a big issue with the RS, depending on how things line up when it's done.


Also looking into getting a new mig welder and a spool gun for aluminum. All this time I've been using a 110v flux core welder, so I think it's finally time to upgrade if I want some nice clean welds. The bare aluminum trans has a crack in one of the top mounting holes. Maybe I can try welding that up myself too if I get something to do aluminum.


UPDATE--Thought I had posted the above earlier but guess I never hit send--

The shifter from the new style (won't spin) and old 633 (can spin) are interchangeable. You can swap the new and old style shifters and the way they work seems to be identical. I took the case apart on the older blue 633 and it looks ok inside despite some water having been in there for awhile. Next the splined axle one will be coming apart. Also I purchased an upgraded welder with a spool gun attachment. Just need to order some shielding gas and I can try it out.

Now I know why it took so long for me to find a trans for my GT, you have them all!

Congrats on the new Mig machine! Should be a real nice upgrade switching over to a gas welder after using a flux core unit.

When I got the Sears I opened up the old 633a and a new style one from the Craftsman GT. Everything swaps over. The advantage to using the newer style diff carrier is it has a 6 pinion gear diff and can be moose knuckle locked or if you do a gear flip you can flip 2 gears making it much stonger. I assume you know this but the side mounts on the newer ones are 2 inches further apart. I don't understand the part about the sprocket. The imput is splined just the output.

Thanks allis! yeah I think it should be way better than the flux powder getting all over. Should save time cleaning up welds and just be better in general.

Mowerjunkie, I didn't know the new ones have the extra diff gears. I saw those ones before (Pics on here of course) but had no idea that all the newer ones were that way. I'll be opening up the new one soon so I'll check it out. Might be good to use the beefier ones. Does the diff separate from the axle stubs? I thought they were one piece though.

The sprocket thing is because I plan on attaching the rear suspension to the 633 axle and not the rear wheels. In other words, the rear wheels won't be attached to the 633 at all. They will have their own axle in pillow block bearings and have a chain drive from the 633 to the live axle. So I'll be using it more like a transmission and not a transaxle. On the 633 axle stubs will be 1" pillow block bearings which bolt to the rear swing arm. They allow the rear suspension to move and keep the pivot point exactly in line with the transmission drive sprocket which will be on one side or the other of the 633. That way, chain tension will not be affected with suspension travel. Motorcycles for example have a spring loaded chain tensioner to keep the chain tight as the suspension moves because depending on how it's set up, the chain will get slack or tight as the swing arm moves slightly away or closer to the forward sprocket. On my setup, the swing arm pivots at the center line of the sprocket, so no matter where the swing arm moves, distance between the two sprockets will not change, therefore, chain tension will not change either.

Once I finish my chassis drawing I'll post a pic of how it will be lined up. I'm working on a top view of the engine, transaxle, front and rear suspension, and parts of the frame.

Interesting project

https://www.agridane.com Specs of agricultural machinery

Your swing arm idea sounds cool. I guess i never thought of doing it using the trans itself as the pivot. I've thought about using the pivot as a jackshaft, though. Same idea.

Ah I understand now I was imagining the suspension completely different. The diffs are the same design the new ones just have two more gears and the 2 inner diff gears are not welded to the shafts. They are splined and held on with snap rings.

I wouldn't do the moose knuckle method even with the extra gears. Safer to just weld them.

RichieRichOverdrive wrote:

I wouldn't do the moose knuckle method even with the extra gears. Safer to just weld them.

The moose knuckle method is pretty badass tho. The nice thing about it is that you never have to introduce heat to the gears. I would have welded if my welder wasn't a massive POS!!

On my Baja sears and the #64 simplicity, I flipped the gears around on those (both older 633). The moose method is basically adding a gear in the newer style ones to jam them up right? Similar idea. Creepycrawly told me those guys fragged a couple flipping them. I never had an issue so far but I didn't run real big tires and also I was working with very limited HP. The Baja sears never saw that many hours of use. The #64 has a bit of run time on it now, but still, pretty mild tires and only 8hp at the most.

Originally, I was afraid to weld it because I ruined a modern style transaxle way back trying to weld it. I had something off and it warped the axle. Ended up cracking the case. I just figured this time I'll weld them up. The good thing about the sears (and I guess wheel horse and maybe others) differentials is that the gears are held nice and straight for you to weld. You can weld them up pretty good and then unbolt to do the inside if you want.

Recent updates...
The older 633 taken apart, Things look ok inside


Case nice and clean


Golf cart I picked up from Doug, in the shop to remove some parts. Saved the rear axle and motor, leaf springs, and front axle


What I really needed for this project was the golf cart front spindles and hubs, 4 on 4" bolt pattern and super beefy


I know the sears fans are gonna be upset again....every time I start a new project I pull a suburban in to disassemble for parts. This time though, I got this from someone with the agreement that I give them back the engine and wheels ect. (That was a year ago, only now getting back to it) Being pulled into the shop with the "Super Snapper" yard tug (Abandoned 2017 build off entry)


The only things I'll probably be keeping from the sears is the transaxle, seat spring, and front axle as a spare for the #64. It's not in horrible condition, just that I already built one and need the parts more than a complete machine.


If anyone needs the fenders or grill ect, let me know and I can see what I can do with it. I'm not 100% sure what parts I'm still supposed to give back to the original owner, if anything

update on the mooseknuckle method since it was mentioned. we did have a failure with it as well, since the inner spline of the added gear engages the axle shafts right beside the c clip. the axle shaft snapped at the c clip slot so the axle shaft slipped out. we took the extra spider gear and bored out the inner spline so that outer gear is the only part locking the diff. seems to be holding up so far.

Thanks for the info. I'm thinking this thing will have pretty high stress on the diff since the plan is to drive everything off one side with a chain. Everything will rely on the locked diff staying together. Unless I run two chains to the live axle, in which case the rear wouldn't even need to be locked technically. But two chains means extra cost, more weight, and more drag. So I don't think I'll be going that route.

Anyone know where I could get head studs to fit an opposed twin (hardened, not just threaded rod) or some sort of stand alone oil pump that will take engine running temperature? Mostly I just see 12v oil transfer pumps which aren't meant for heat.

I saw your question about oil pump on sprockets garage, posted a link there for ya, also got two options for ya on the head studs. Mcmaster Carr sells grade 8 threaded rod fine and course thread, you could make your own for cheap. or if you call ARP with the thread and length you want, Ive heard they are good about getting you set up with studs mismatched from the kits they make. as in they make so many different studs they have just about all sizes made already and can usually get you what you need but its not gonna be super cheap

I could use the starter/gen off of it lol.

I think the grade 8 threaded rod would work if you could get some of it. I don't think the original bolts are any stronger than grade 8.

I think with the force of a locked diff being distributed as well as it is among the 3 sets of gears, welding them won't affect the gears enough to matter. But what do I know.

Alright thanks guys, I'll check into it and see what I can find.

The oil pump plan was to pull oil from the sump in the engine, run through a cooler, then back inside the engine to a squirter which would squirt a stream of oil onto the bottom of both pistons in the opposed. I figured with a supercharger (which I'm planning on using) I'll be burning a lot more fuel and making more power. That means more heat. I figured I'd keep the stock pistons from failing under high boost (maybe) and also keep engine temperatures down. Whether or not it's necessary to do that, I don't know.

Disadvantages to using the oil pump...It's going to cost some hp. Maybe not a lot, but at least some. For one, you'll have to drive the oil pump. Either mechanically or electrically. Even driven electrically, a load on the charging system drags on the engine a certain amount. Also, the excess oil being thrown around the crank case and clinging to the crank, rods, and everything else puts some drag on things. How much more than the stock splash system? I have no idea. But I know it would be quite a bit more since the stock system almost certainly doesn't throw that much oil around. Lastly it will add some weight to the machine. And that's the last thing I want to do if I don't have to, especially if it's something I don't need.

Advantages...Engine temperatures reduced significantly and no lack of lubrication. With a decent cooler in the line, I'm sure you could shed a large amount of heat from the engine by running the pump. Air cooled engines aren't known for staying all that cool. And from what I hear briggs opposed's aren't known for the stock oil system being all that great. Maybe the issue is worse on the vertical shaft engines where the upper rod is a bit too far away from the slinger. Or maybe the issues are mostly from people letting the oil get too low. (In other words, the opposed's are less tolerant of low oil than other engines?) At any rate, with the oil pump, you could be 100% sure you have plenty of lubrication no matter how hard you want to beat on it. Still not as good as a pressure lube system, but I'm not trying to turn 8500rpm or anything like that. Of course........a not so important advantage would be that the big oil cooler on the side would look super cool.

What do you guys think? Worth it or not really? I'm still thinking about it.

Personally if I was going to convert to pressure lube, I would do a dry sump. That would cut friction a bit and would also direct some heat away from the engine. You could run an oil cooler in line going from the engine back to the oil tank. This would keep your oil reserve cool. I’d really like to see you do it, but would it be absolutely necessary? Probably not.

Most cost effective way would probably be thinner oil and run a little more oil than specified. Thinner viscosity would fling higher to the upper rod and would reduce stress on the plastic gear inside. One step better would even be a custom machined billet oil slinger that would be more durable and you might be able to tweak the design to make it more effective/efficient

Sorry for the double post, but I think what I’m going to do is run diesel oil in the vanguard on the mk2. Can get it in synthetic and I believe it’s stronger than typical gasoline engine oil. What I mean by that is it would take more force to squish it out between the crank and the rod “bearing” and the reason I think that is because of the nature of Diesel engines. They have such high compression and are compression driven engines, the forces in the bottom end are just immense.

And you wouldn’t necessarily need real thick oil. The 6.7 powerstrokes from 2011 to current specify 10-30...I do a lot of oil changes on those. But anyway our OPE engines specifically call for SAE 30 oil. Is the viscosity scale different between gas and diesel oils? I have no idea.

Anyway it might be worth a try. Thin diesel oil with a metal oil slinger and run a little more oil than specified. And if I said anything that’s incorrect somebody please let me know. I tried to explain my thought process as best I could but I may be totally wrong

Yeah I'm kinda on the fence about it. I still have some time to think it over though, probably won't be starting on the engine for a little bit longer.

Interesting ideas though. And I was thinking about a dry sump system too, but my issue is that I wasn't really going for full pressure lube. That would be great If I had a pressure lube opposed with the passages already drilled, but not sure if I want to convert it myself. And my spray system would fling a lot of oil around if I only did it that way, so that would defeat the purpose. Ideally yeah, the best way would be full pressure lube and dry sump. I know some race guys even pull a slight vacuum on the crank case and they say that keeps even more oil vapor out of the air.

Another thing is if I should try to go with heavier duty pistons or not. On ARC's website, they do have what are supposed to be better pistons available for the opposed. But not sure if that's worth it without boring it. I plan to at least do billet rods and a flywheel. Might get some slightly heavier valve springs so I can crank it up a bit more without valve float. If the stock pistons will hold together it would be ok. Not sure how they will do with the boost.

Probably just run this one stock till it blows, and in the meantime look for a 46 cubic inch oppy to swap in later, built or stock.

I assume the one you have now is a 40 or 42 right? Could play around with stroking or destroking it. Depending on what you want your powerband to be

I have two 42CI's. I would go with a 46, but I think they are a bit more rare to find blocks. Especially horizontal models. Blowing up a stock engine is fine, but for the Top Tractor challenge next year, I can't have it blow up during the event.

At any rate, my plan is to have a naturally aspirated engine with stock rods and parts for testing purposes. That might be around 10hp down on the supercharged race engine, but I'll be able to beat around with it to test out the chassis once I get the thing built. At least get a good feel for driving it so I can practice without wearing out the good engine.

I tried to find some copper head gaskets which they used to make for the opposed, but now it seems all the mower racer guys have moved to more modern engines and a couple places I looked don't have anything for it anymore. I think the last opposed was made somewhere around 1999 so it's been awhile. I could make my own if I need to. Who knows, maybe the stock ones would be ok.

I really need to get moving on this built so I have plenty of time to trouble shoot. Hopefully I don't have to many major issues to work out at the end, but I'll be getting into some unknown territory this time with the supercharger.

I think with boost you’ll want the lower compression ratio a thicker gasket would give you, and that will increase the flow from the valves into the combustion chamber. Wouldn’t have to have as big a ring gap either

Briggs lists all their flathead engines as 6:1 compression ratio and OHV engines at 8.5:1

Compared with automotive engines, that's already fairly low, so I think I should be alright that way. I wasn't trying to increase the compression ratio with the copper gaskets. I was just worried the stock ones may blow out. I could potentially remove some material from the heads to get better flow if needed. But I planned on just leaving them stock and seeing how that goes.

Some other compression ratios for comparison.
Model T Ford, L head- 4.5:1
Briggs opposed twin, L head- 6:1
Lancia 037 supercharged 2.1L, ohc- 9:1
Chrysler 426 hemi, ohv- 10.25:1
2001 Toyota echo 1.6L, ohc- 10.5:1
1988 Mercedes 2.5L turbo diesel, ohc- 22:1

Hopefully it will be ok on premium pump gas. I'm not planning on getting too out of hand with boost pressure so I would imagine so. Time will tell.

Oh ok I gotcha. I assumed when you said copper head gasket you were running it because it was thinner to boost compression. Didn’t think about copper gaskets being any number of thicknesses haha. My bad