1995 MAX IV Rebuild Thread (Gary's)

[2gnospam]

I have decided to start a thread to document my rebuild. The MAX IV will get new axles and sprockets, engine mods, changing of the shift levers and such to tie rods. New roll cage which will tie in to the frame and outside rail to prevent body sag. Relocation of battery and removable seats for cargo storage, etc.

That being said I am looking for input on roll bar tubing sizes:

1.) what is the typical roll bar tubing size and wall thickness?

2.) How about the angle iron used around the frame?

[jpswift1]

The roll bar tubing used by Recreatives is 1 5/8" black pipe.

[2gnospam]

Been doing a little research today. The area I live in does not have a good supply of steel sales companies (for round roll bar tubing for example). Thus most stuff has to be mail ordered. I decided to look at the cost of different steel options for tubing. As such there are some advantages using Cr Moly 4130 for roll bar tubing particularly for strength per pound, and in some cases strength per dollar. I put together a simple spreadsheet (see link below) that compares the performance of the steel offerings from Aircraft Spruce 4130 tubing as a function of cost per foot, weight per foot, cost per pound, tensile strength per dollar (how much force it can take on axis (for one foot length) per dollar), and bending strength per dollar. Results are somewhat interesting and I ended up landing on 1.5" x 0.083" at $4.95 per foot for my roll bar ($3.89 per pound, $0.15 dollars per foot per 1000 pounds of yield strength in tension)

https://docs.google.com/spreadsheet/ccc?key=0AkEmM1eBzQDVdFFiZkN3UWRQN0wycUFtV0l6U0lfM0E

[thebuggyman1]

The problem with statistics is you can make them say anything you want to. The strengths listed are from a test lab, not real world. The problem with thin walled tubing is it dents easily, and once dented it loses it's strength. .083" is probably fine for an amphib that is not likely to barrel roll, it would probably just roll once. The next issue is welding. Chro-moly is best welded with a tig welder.
Often the best place to buy roll bar tubing is a race car shop.....they go thru alot of it.

[2gnospam]

Fortuntely there were no staticstics involved in the spreadsheet. It is just basic strength of materials math which looks at ideal strength of 4130 steel tube in pure tension or bending. Really just a way of comparing different sizes of 4130. When considering the type of steel to be used it is a matter of preference. All steels must be suitably and appropriately welded. Generally 6x6's are used recreationally and are not in the same class as high speed racing thus most steels (ERW, HREW, DOM or 4130) would be suitable. To each his own. I am just informing the forum what I am going to do and why.

Given the high strength of 4130 (90,000 psi rated yield strength) it will be less susceptible to "denting" then a lower strength mild steel in the same thickness. Proper use of 4130 can result in a lighter cage for the same strength. In the aircraft industry where strength to weight is paramount, you will see the use of 6061 and 7075 Aluminum and 4130 steel used.

Most racing sanctioning bodies permit (and encourage) the use of 4130 in addition to 1020 mild steel. Please see the rules for SCORE (Score International - Off Road Racing, sanctioning body for the BAJA 1000 race), NHRA, SCCA shown in the links below). 1.5" x 0.083 is suitable for vehicles under 1500 lbs (less driver) in racing conditions. Some sanctioning bodies require TIG welding (NHRA) of 4130 and some permit TIG or MIG welding (SCORE). SCCA requires additional thickness for steels which have a weld seem (ERW, see link below) "1501-2200 lbs 1.500 x .095 DOM / Seamless / Alloy or 1.500 x .120 ERW". Again we are not "high speed racing" but the recommended materials and methods by the below referenced sanctioning bodies (developed over many years of competition and accidents) can provide general guidelines for construction.

NHRA:

http://www.nhra.com/UserFiles/file/General_Regulations.pdf

SCORE:
SCORE RULL CAGE RULES UPDATE

SCCA:

http://sports.racer.net/docs/rules/2002/sect_18_roll_cage_and_chassis_2002_gcr.pdf

[hydromike]

I can appreciate you wanting to get the most "bang for your buck", but unless the goal is "overkill for the buck", I'd stick with plain-Jane welded-seam tubing. I respect your interest in safety, and there are a lot of interesting specs you've laid out above. I've made a few roll cages for comparably lighter Attex race machines for myself and a few other folks, and the stuff holds up just fine. The extent to which they've been tested has been limited to low speed (<20 mph) events, but JP, GeoJem and I have repeatedly stressed similar back-yard designed and fabricated units with the most damage being scuffed paint and a few reflected curse-words (Rustoleum semi-gloss seems to deflect several combinations of four-letter words the best.... additonal test results to follow).

I'll have to admit that the CREW steel lends itself to a heavier cage overall, but for the quantity used in a Max IV cage, what's the overall weight savings using the 4130? You're absolutely right when you say it's a matter of preference. I think JP's cage is composed of old rejected gas pipe picked up at a scrap yard at $0.35/lb. Ride hard JP.... ride hard.

[2gnospam]

Understand your points. No doubt overkill to use 4130. I am estimating the weight of the whole cage to be about 60 lbs (thus the real weight savings can only be about 10-20 lbs). If I had a reasonable supply in my area for mild steel I would likely have gone that route. I did not think to check the local metal scrap yard as it could have had something suitable.

We will see how the cage turns out as I am adding a few other ideas that I have got from other forum posts. I plan on tying the cage directly to the frame and also to the outer rails (like the factory cage). My intention for doing this is to provide anti-sagging support for the outer rail via vertical support from the frame. I plan on doing initial fit and welding with body rails lifted slightly. The 26"x12"x12" tires have good clearance and don't want to loose this by sagging. Also, want to relocate the battery to beside the engine and move the back seat rearward a few inches. Probably go with a single seat in the front. Will make storage rack on back and rear seat removable by quick release pins (as I need to use the unit to haul stuff up and down a steep hill at the lake). As most of my lever joints are pretty worn out and sloppy I am going to use tie rods and rod ends. Have purchased most of the parts at this point and will be bending tubing early next week.

[2gnospam]

Ordered a set of SS Vampires 27x12x12 (VAM-38) for $593 delivered. Now I hope I can make them fit

[jpswift1]

Ordered a set of SS Vampires 27x12x12 (VAM-38) for $593 delivered. Now I hope I can make them fit

Those Vampires are GREAT in the mud! I've personally seen 27x12x12 Gators on a Max IV, but not the Vampires. If they don't fit, just heat the tub a little bit and reform it and you should be good to go. And of course, we'd love to see pics!

[2gnospam]

Will do. Just made side skirt angles Wednesday and started bending main roll hoop/cage bars. Should be back on it Sunday. Also bought tire tubes and am going to use tubes and low air pressure (~2 psi). I hope tube/tires do not rotate on the rim. Will also sandblast and paint the stock rims.

[2gnospam]

MAX IV Roll Bar Cross Section.jpg
I am adding a tub surround angle iron to have multiple locations to tie in the roll cage and mount the winch. This is a sketch of the roll cage and frame tie in. The front and rear hoops will be similar to stock but will have cross supports that will serve a couple of purposes. First they will permit bars to extend down and mount to the OEM frame (to prevent body sag). Additionally the rear cross piece will be the attachment point for a removable load carrying basket. Front cross member can act as a driver grab handle getting in and out, etc. I will also add down tubes in the rear to tie to the body surround. The basket (expanded metal), front and rear seats will all be removable via quick release pins to permit easy access to the drive train and reconfiguring for more cargo hauling. The basic idea here is to allow all of the passenger and storage rack weight to transfer to the wheels via the original frame. The roll hoops will act as body side supports (anti sag) and be there in the event of a roll over. Fab is coming along nicely. Main hoops are built. Working on the remaining portion of the tub surround tonight.

Have now ordered new axles from Whipper.

[kghills]

You will find that the support bar in back of the front seat might be a bit low. The height you have shown translates to about knee knocking height in my Max. By bringing it up to about the top height of the back of the seat or a bit above allows it to actually function as a grab bar not only for when driving but also for entry and exit of the vehicle. Also any cross bar that is low in the drivers area would be a possible knee banger also. The factory tubes on my cage are 1 5/8 so bringing anything that size into the tub seemed to take up valuable space.

Keith.

[2gnospam]

Thanks for the input. I have the main hoops tacked in. Had planned on setting the rear hoop cross at just above the engine height to allow mounting of a basket. The front bar is to be installed above the front dash about 1.5" I was going to do some trial and error on the middle bar as I can understand your point. Additionally I could go a bit smaller on the vertical bars (going to the frame) as they are primarily in tension and compression. I usually do a lot of sitting and thinking and looking before deciding. Again thanks for the pointers.

[Dan67]

Will do. Just made side skirt angles Wednesday and started bending main roll hoop/cage bars. Should be back on it Sunday. Also bought tire tubes and am going to use tubes and low air pressure (~2 psi). I hope tube/tires do not rotate on the rim. Will also sandblast and paint the stock rims.

Tires have been know to occasionally spin on the rims. Most times you won't even notice it. On brand new tires, I would not use tubes. Only on older dry rotted tires that just don't hold air, then use tubes. But if you really want to use tubes, you will have to glue the tire beads to the rim. I use Permatex High Tack Gasket Sealant. You can find that stuff at just about any auto parts store. http://www.permatex.com/products/aut...et_Sealant.htm

[2gnospam]

Was wondering the best way to run very low air pressure and not spin the tires. Sealant sounds like a good alternative. Does anyone have a good or bad opinion of using sheet metal screws (in conjunction with tubes).

Thanks