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

#Buildoff2022

Simplicity Broadmoor 728 XC. The fender is just mocked up in this pic, not attached. What I’ve done so far is started the front axle and frame. The frame is probably about 20% done at the most. In case anyone is reading this and hasn’t seen the other 2 or 3 build threads that were started on this, the plan now is to build a low center of gravity machine for the TTC. Front suspension, single link wishbone setup, sears suburban 633a transaxle, sears suburban steering and close to a sears suburban wheelbase. I think we’re gonna be at about 44” and 42” wide? Trying to keep the weight down as much as possible. Might use some aluminum parts and my original plan was always to use fiberglass for the hood and rear fender. I’d still like to try that but we’ll see. So that’s about it, we’ll see how it goes! I might try to do video updates here and there which I really haven’t done in the past.

[adm]Welcome to the competition!  I'm familiar with the build.  Plus @Doug already OK'd it.[/adm]

You should post your mockup pix you had on FB.  The people here that didn't see it will get the Idea of the build.  Very nice!

Thanks! Well here's some pics I took last night when I mocked things up with the Simplicity Adventure edition hood. The rear fender fits over the back end pretty well, except for being a bit narrow. Plastic fender flares may be a good idea to keep mud from flying all over.

The engine needs to be that far left because that's where the belt lines up. I really didn't want to add a jackshaft on this build because it adds weight, saps power, and takes a lot of room. Plus it's an extra belt to deal with. I think with the seating position, your left leg should clear it ok without it being too much of an issue. I can also remove some steel from the corner of the fan shroud and re-weld the corner to gain an inch or so in a worst case scenario.

Obviously there will be somewhat of a weight bias to the left side of the machine. The battery location may be used to help compensate that.


The hood may end up being a bit higher than in these pics. Also, the grill and hood will probably be moved forward about 3" in order for the grill to clear the front shocks. Unless I change my mind about shock placement and they end up out in front. In that case the grill location may stay on the axle center line, or get moved back.


Originally, I was going to have IFS and I built this front end. Unfortunately, it ended up being much heavier than I wanted at around 40 lbs. And I had issues getting the steering rods to clear the arms. Not only that, but ground clearance on my old frame and IFS design would have been a problem for the TTC. So, I decided that it would be best to stick with a more conventional setup and I went back to the mono link wish bone design used on the adventure edition. Only this time, I used golf cart hubs and king pins and built my own axle from 1" square steel instead of using a sears suburban axle. The sears axles with the drop down spindle are too high and I want to keep the weight down low. So now, the axle is level with the center of the wheels. Ground clearance will be about 7-3/4" at the steering pivot. More than enough for how narrow the wheels are (we hope).

My theory is that there isn't any point in having the tractor any higher than it needs to be. If you can just touch the top of a rock and you get through without a problem, that's the goal. Because any higher is just wasted height which will tip you on turns and hills. I think this is going to be about the limit of how low you can go for an off road machine. Time will tell if I went too far.


One thing I don't like is having the steering rods hanging down where they can be hit on stuff. But it's kind of complicated to get around that. Not without adding some heavy U joints and that sort of thing.

Golf cart outer tie rod ends. Drilled pockets in the end of them for my go kart tie rods to fit in before welding. Inner ends are heims.


I cut the sears suburban steering pivot down quite a bit, drilled a couple lightening holes. Welded it into the front wishbone and added a rod to brace it a little extra.


Next step is to finalize the wheelbase and make the bracket that holds the wishbone pivot. Once that’s done, I can start figuring out the shocks and forward frame.

@mr.modified you certainly do some nice fab work. looks like this should turn out pretty slick !

Thanks, hopefully I can get the thing finished this time.

I lined the engine up more or less and drilled the mounting holes in the frame. Had to take the frame back off the transmission to finish drilling the holes in the drill press. Going through the second side of the tube wasn’t too straight with a hand held drill. Finally got everything pretty close.



I also finished a couple welds on the bottom of the frame and welded the 5” trans pulley on after removing the hub from the original pulley. It was a bit of a process but ended up pretty straight. I hope the gearing will be high enough with the small back wheels, if not, I’m not sure how much farther I can go with the pulleys. 7” up front and 5” in back. I might be able to get away with an 8” up front.


Decided we’re trying to be professional here and I better fix up these square ends on the back of the frame. Cut them and welded them back in. I think they look a lot better that way. Didn’t get a chance to do the wish bone joint bracket yet but that’s gonna be soon.

Nice work! Good to see you back on the project!

Thanks!

Meanwhile, in the engine department… I’m trying to figure out which block is in the best shape. I have several to choose from, but some have more port work done than I’d like from the previous owner. Some have a bit too much wear ect. I plan on building two engines, one main engine and a backup/practice engine.


Here’s a stock engine that I need to disassemble. Hopefully it’s in really nice shape but it’s hard to tell until I take it apart. It’s also a vertical shaft engine but the blocks are the same.

I know your engine is offset for the engine driveline.  Do you think there will be any hurdles to contend with because of this?  Like Left side weights being much more than right side?  Tipping factors for right hand turns?

Brace for my usual long as heck explanation...

Yes, I imagine it may somewhat favor left hand turns, but I don't think it will be quite as bad as it may look. It's roughly 3"-5" off center, depending on what you count as the center of the opposed. If you want the weight of it completely even, it might even be 6" over, but no more than that.

On a normal tractor with a factory frame, this might be a pretty significant problem. But there's a couple things I have going which will counter act that and I don't think it'll be too big of a deal. The first thing is that my engine is mounted a good 6" lower than most other machines. Generally speaking, everyone is running somewhere around the height front tires that I'm using on this build, and if you look at pictures, usually the bottom of the engine is about flush or higher than the top of the front tires. So being off to one side won't be as bad with my lower center of gravity as it would be if the engine was way up there like they normally are.

However... I have thought about mounting the battery near the front and staggered to the right side of the frame to help balance it out. Depending on brand, the standard size lawn mower battery is between 20-25lbs if I use a normal lead acid one. I'm a bit on the fence about finding some other battery because I'm kinda worried about capacity. I know there are some smaller, lighter choices out there.

Worst case, even if I use a lighter battery, I don't think it will be something to mess it up too bad. I'm sure it will be noticable, but I'm thinking it will be no worse on right hand turns and side hills than any other machine.

I also decided to measure my wheel width today and found out I'm at an extremely narrow 34". I forgot it was that narrow. My IFS design was going to be around 42" which is about as wide as you'd wanna go for the TTC. My previous research showed most people were somewhere around 40-41" wide. I'm planning on keeping any other weight higher than the wheels as low as possible. There will be a top structure over the engine as a frame brace/stiffener, and that will either be 16g steel tubing or possibly aluminum. Aluminum would require being bolted on and extra time to fabricate and track down materials, so that probably won't happen.

Super build tip, when you drill a hole, just touch it with a bigger drill bit to clean up the edge.


Making the shock mounts for the front axle. Cutting them out of some sears suburban frame parts.


Another super tip, if you don’t want to be real careful starting your cut where you want, you can clamp a vice grip on the piece your cutting and hold your saw blade against it till you get the cut started.

That's some good tips right there! Next time you want to chamfer a hole, bust out a uni bit (aka step drill), it's provides a super clean chamfer!

Shock mounts cut from the finest 1970's Sears Suburban frame steel and ground to shape,
ready for welding


Stack of washers hold the brackets so they don't move while welding and keep the holes aligned.
I keep the brackets spaced out a bit wider than the shocks will be and shim with a washer or two later. That way if I switch to wider shocks or have some alignment issue, I have
some room to play with.


Welded on


Front axle is done except for a mount or stud up front for the pan hard bar


I will probably end up using RFY coil overs again like these from the Simplicity adventure edition.
I would like them slightly stiffer than these which are "supposed" to be around 200 lbs. But most
listings don't even have a spring rating. It's kinda hard to tell what you're getting.


Making progress though. I ended up ordering some larger rear tires after conversing with some expert tractor off roaders and doing some thinking about the mud at the TTC this past year. They won't be as big as most guys are running but larger than the 18's on there now. We'll see how that goes when they come in.

Looking MINT!

Going to be quite a rig I think.

Thank you. So far I think things are on track. Here's a couple of pics from before when I was starting to build the front axle.

Knuckles and hubs from golf cart axle


Trying to line everything up straight with a piece of 1" square steel


Welded together. It was kinda tough getting it straight, but it turned out
a lot better than I thought it was going to. The rest of the wish bone
turned out pretty good also.

nice job on that axle. i'd say getting it straight with those angels would be pretty tough. but looks like you got it !

@MightyRaze wanted to just point out that this thread is not labeled as [22 BO]… (sorry my ocd is getting to me )

Nice work on this thing @mr.modified! Can’t wait to see the finished product! Been a long time coming lol!

Thanks. Today didn't see a whole lot of progress. Had some other places to go, but I did pressure wash the outside of this engine. It's a 40 cubic inch earlier opposed, but the engine blocks are the same as far as I know. So far all the threads for the manifolds ect are good and there's not too much cylinder wear. That should make this one a decent start for one of the engines.

I'm kinda waiting on my new rear tires to come in before I fab up the bracket that holds the front axle. So meantime I'll work on some engine related stuff. This engine is also a vertical shaft, but I'll swap in a horizontal crank and the other parts. Basically just need the bare block.

New tires have arrived. Decided to change my original plan a bit and go with slightly bigger tires after several people suggested it and after a lot of thinking it over. And..... after seeing the Top Tractor Challenge get more and more mud in the past couple years.

Tires were previously 18x8.50-10 I figured those were fine for front tires and that's about as big as anyone goes up front more or less. I wanted to keep the weight down low, so I was gonna run those in the rear also. But there are a couple disadvantages. The transaxle sits a lot lower and it's gonna drag in deep mud, and the smaller tires also aren't going to climb up on rocks and things as good. The low side wall makes them super stiff, so dropping the pressure isn't going to effect them as much as a bigger tire. There aren't many options for really aggressive tread in the small size either.

These are 22x8-10. I tried finding 22x8.50-10 or even 22x9-10, but those weren't an option. I think 22x8 should be alright and I prefer a thinner tire on this build anyway as I think it'll dig through the mud better and also save weight. As long as it's not too narrow for the rim which shouldn't be an issue.


Small rear tires 18x8.50-10
Advantages:
-Less weight
-Lower center of gravity
-Probably quicker acceleration because of the smaller diameter
Disadvantages:
-Not high enough to claw over deep mud
-Not tall enough to roll up on ledges
-Makes your tractor look like a friggin go kart!
-Stiff tire doesn't flex
-Small diameter means gearing too low

Larger (kinda) rear tires 22x8-10
Advantages:
-Larger diameter rolls up over things better
-Higher side wall has more flex = better grip on rocks
-Deeper tread options available
-Higher gearing with larger diameter, 633a is low enough as it is
-Makes the build look more like a tractor
Disadvantages:
-More weight
-Higher center of gravity/moves transmission and frame higher

I think for something like hard packed dry ground, like a circle track or steep hills ect, the small tires would be an advantage. But for the TTC, I think the mud and rocks are going to out weigh any benefits the small tires may have. The 22's are still lower than most other builds which means we should still have a center of gravity advantage of a few inches. The engine section of the frame I can keep about the same level as it is now, so only the transaxle will be a couple inches higher. That ground clearance in mud is going to be worth more than the slight height issue. Thanks to creepycrawler and redzz02 for suggesting I reconsider my tire options. I think it's probably the best way to go.

Got the new tires mounted and they seem to be about what I was looking for
The frame is going to need some adjusting now to account for the new rear tires




Opposed stripped down to a bare block.

Finally ready to make the brackets for the wishbone pivot. It’ll use a half inch bolt. The bracket will be welded to the forward engine cross member.

Ahhh, are you sure cardboard is allowed for use in the buildoff? I think that's definitely cheating, it would make your rig too fast and light, not really fair to the other members who can't afford cardboard and have to make their tractors out of steel.

@mr.modified is a master cardboard fabricator and is allowed in the build-off!  LOL

I actually used an entire cardboard hood and grill on my machine during the 2020 TTC to save weight. It had a 1/2 electrical conduit frame just to hold it. The cardboard was zip tied to it and painted. Desperate times call for desperate measures. I shaved 66lbs off and took a 4th. Grill was drawn on with a marker...

So I'm not afraid to use a little cardboard here and there I actually got the brackets all fabbed up today and I'm getting close to having a roller. I'll post a few pics later on when I get a chance.

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