[DNF] [22 BO] Simplicity Broadmoor 728 XC Build

Does that rocking live axle type suspension actually do anything? I understand the theory but can't really see it doing anything

TechnoChicken wrote:

Does that rocking live axle type suspension actually do anything? I understand the theory but can't really see it doing anything

I was inspired by the monolink on that tractor and @redlinemotorsportts MTD.


At low speed it can help hold the front tires on the ground.  Where I saw it work the most was at Haspin Acres.  I could run across the flatter parts of the trails as fast as I could go (30ish) very smoothly and with no death wobble at all.

This video shows my previous wishbone front suspension in action at 0:40, 1:29, and especially 7:58. While it's not the most high tech design if you want a lot of travel and you want to go 100mph off road, it works pretty good and has plenty of articulation for a tractor. Ford model T's and A's used almost the exact same front end setup with a wishbone. The only difference was a leaf spring instead of the coil over shocks, and because they used a leaf spring, they didn't need the panhard bar that I'm using. But the principal was the same. Also a lot of cars and trucks used to have solid front axle setups, just without the wishbone (Two parallel leaf springs instead). I get somewhere around 3" of travel with the setup in the video. That may not sound like a whole lot, but it's A LOT better than no suspension and it keeps the front end from dancing all over on rocks.


Here's an articulation shot from Haspin 2018

I apologize for the double post but I have a hard time getting pics from my phone on here.


Cut these brackets for the front wish bone pivot. Steel from a sears suburban frame.










I hate to add extra weight but I added this to the front axle to protect the steering. It hangs down below the front axle a bit.

Beautiful work man!

We ARE watching an artist at work.

Thanks a lot. I'm making a little progress anyway.

I'm almost ready to work on the rest of the frame where the frame goes up to the top of the shocks. I ordered some new RFY shocks for this build. I had some shorter ones (white shocks from earlier pics) but they are like 700lbs and a bit short. Plus, they don't look as cool as these. So, these blue ones are supposed to be 280mm length and around 395lbs. The old yellow ones from the Simplicity Adventure Edition are about 200lbs and 320mm if I remember right. So these will keep the weight a little bit lower and will be slightly stiffer. I plan on having them at a bit steeper angle than on the Adventure Edition, so they will need to be a bit stiffer to account for that. Also this build should be a lot faster, and therefore need a bit stiffer suspension. On the other hand, this build should end up a lot lighter than the old one. A bit of guess work is involved, but we'll see how it goes. Worst case scenario, they do have various spring rates available in 280mm, so I can always swap to different ones.


Here's how the shocks were mounted on the Adventure Edition. You can see they are mounted at a slight angle, but almost straight up and down. On the Broadmoor XC, they will be mounted at a steeper angle, with the tops of the shocks almost together. The bottom mounting, on the axle, will also be a bit closer because the front axle is a lot narrower. That's because of the wider front tires and the golf cart knuckles being a bit different spacing. I have to wait for the shocks to come in before I go too much more on the frame, so I can line things up exactly.

Most people mark it on cardboard and then make it with steel, this guy is a legend, he marks it on steel and then makes it on cardboard

I don't know about all that but almost lol.

Well, latest news from Simplicity HQ. The blue shocks are somehow sold out after I ordered them, and I was offered some replacements in a different color. So I went with yellow. Same size, same shock, except the yellow ones have 242lb springs instead of the 300 something the blue ones were supposed to have. I may have to mount them at a different angle to compensate for that. But we'll see.

Tonight I did a bit of figuring on the brake system, seeing where the cable will run and how the new brake band will attach. I also removed some un-needed weight from the frame. Note the top transmission mount which is now scooped out a little bit. As soon as the shocks come in, work on the forward section of the frame can continue. I'm not sure of the frame weight so far, but once it's complete, I will weigh it. There are areas where I could safely remove some decent chunks of steel from the front knuckles and rear hubs. But it would take some time. I'm trying to focus on getting the thing built before I go too crazy on weight removal. I think I can skim some more off that rear sears section too (the blue part).


Meanwhile in the body and paint department:
I'm pretty sure the frame will get painted orange just like the stock ones and the adventure edition. There will be bracing running over the top of the engine from the upper shock mounts to the top of the dash. That will be part of the frame strength and also hold the hood. I bought some 16g 3/4 square tubing for this purpose. Since that structure will be supporting the full length of the hood, it can be extremely light duty and just needs to be strong enough to roughly keep it's shape. The rear fenders are supposed to look somewhat like the stock tractor. But that might be a bit of an issue with the size of the stock rear fender and the seat location. We'll see. I really want to at least have the rear "triangle" sort of back edge showing that's on all the 70's Simplicity's.

I like the orange paint on your other tractors, think you should stick with it here? Is there some kind of calculation you can do with the weight and shock angle to calculate what shock you need instead of just guessing?

I’m sure there’s some formulas I could use to figure the shocks out for sure. But it’s not so easy to find the exact weight springs you’re looking for usually. I’m not even sure you can trust what the description says anyway on those rfy shocks. Some of that stuff you don’t really know if the listing 100% goes with that shock. If you were buying $500 shocks then you’d probably be getting what it says but who knows. It shouldn’t be so far off as to be a serious problem though.

I kinda like the orange too. I used rustoleum before I think and the color is actually a little brighter than the simplicity color.

The new rfy shocks came in today. You can see how they’re a little shorter than the shocks from the adventure edition. A bit shorter stroke also. Now I can start on the forward part of the frame. I may locate the battery in front of the engine but we’ll see.


I forgot I was cleaning the one engine block out behind the garage and it got iced up a bit overnight. We had some freezing rain.

Figuring out the bracket for the upper shock mount


I wanted to have some adjustment holes for a soft and stiff setting. I couldn't get more than two settings because with the frame being mounted to the bracket, there wasn't room for more holes. As it is now, it's a little bit snug to get a wrench or socket on the bolts, but it should be alright.


Marking out another piece for the front part. I could just mount the shocks from the one side, but I never really liked doing it that way. The upper shock mount is where the whole front of the frame will end up. 16 gauge 3/4 square steel is what I plan on running over the top of the engine.


I drilled the mounting "eyelets" in the shocks to fit 7/16" bolts. Top and bottom. Originally they were some metric sizes, but I don't like using metric bolts

Educate me please, what are the cans hanging off the sides of the shocks?

Nevadablue wrote:

Educate me please, what are the cans hanging off the sides of the shocks?

Spare beer, just in case you run out
I think the other use for them is they are part of the oil shock system, I could be wrong though...

@Nevadablue  They are gas or air charged.  On the bottom of them is a Schrader valve and you can add pressure.

Thanks! I didn’t have any idea how they worked, I’ve never seen them before. Pretty neat gadgets.

Fastman wrote:

I think it is self explanitory as to what they do.

no question is a bad question that's how people learn !

diddie wrote:

Fastman wrote:

I think it is self explanitory as to what they do.

no question is a bad question that's how people learn !

Big thumbs up to that, I apparently didn't know exactly what those were, you live and learn

Nevadablue wrote:

Educate me please, what are the cans hanging off the sides of the shocks?

They're oil reservoirs. I guess as the shock compresses, the oil flows into them. Not sure if they have some sort of diaphragm inside with the air pressure on the other side or what. I never actually did much research on the inside of one. They also have remote mounted ones with a steel braided hose running to it from the shock, instead of it being made part of the shock as they are here. Part of the purpose may also be to keep the oil inside cooler.