Steering pump disection

[Mbrantley]

So since I toasted the P.S. pump at the gathering I thought it would be a good opportunity to dissect the infamous p-pump and post my findings. First off the pump I had on the buggy was a not a stock pump, it was purchased from one of the main off road steering system shops spec'd for the highest pressure and flow possible for this series pump, secondly the pump was doomed from the start because some novice left a soft plug in the suction line however this would not have caused the splines to twist and the shaft to bend. If it didn't die at the gathering then it would have soon after.

I was hard to get pics of all the damage but you can see in the first two pics that there was allot of galling on the side plates and the splined section of the shaft was twisted and bent. This went along with a galled main bushing and pulley.

The Thrid pic shows the main difference between a stock pump and the "high flow" pump, the ring and rotor are substantially wider producing the higher flow. The other difference would in the control valve section, orifice size of the output fitting and the bypass pressure. This is where the differences end. Of the multiple pumps I have torn apart all of the castings are dimensionally the same, This is important to note because the suction passage is marginal at best for the low out put pumps and there is not alot of room for the fluid to flow to the inlets, secondly the fluid is making multiple turns arround sharp corners, inviting cavitation.

I have since replaced the pump with another p pump that I did a fair amount of port work on to tide me over and also added a large tube & fin cooler, and a separate inline filter rated for 8gpm in hopes to reduce operating temps as a precaution even though I did not see any signs of excessive temps.

If you read through all of this and are saying WTF? my buddy has this or that and is running a stock toy pump or what ever... The steering system on my buggy was designed with only 2.3 turns lock to lock and I am demanding a very fast transit time and it is now evident that this series pump cannot meet the system demands and I am done throwing money at sub par band aids. I plan on moving up to a larger steering pump from the medium duty truck world.

Matt

 

[crusier72]

Nice work on the education. To bad it cost so much pain in the a$$.
I can't wait to see you're solution to the problem.
Lets get it done.

 

[Mbrantley]

I am leaning towards a "Big bearing" Sag Pump I believe that it has the same displacemanet as the aftermarket pump I destroyed but the casting design allows for more flow capacity (using my calibrated eye ) . The other pump I am looking at is a Eaton BB, this pump maybe too much for my application with 6gpm @ 1200 RPM I have some doughts that my system could handle the flow at 6000 RPM . As is being covered in other forums now the issue at hand for these type steering systems is if we spec a pump for the flow and pressure we need at idle then when you are bouncing off the rev limiter the pump is producing way too much flow....

Matt

 

[rblank]

Well you certainly showed that pump who was boss!! You have a score to settle with the Devil's Bunghole and The Gultch.

 

[Mbrantley]

I Will definatly attack the bunghole again...
maybee with proper steering I will fair better. Have you ordered tires yet for your runner?

Matt

 

[rblank]

Not yet But I patched the slice I have for now. I only have one more run that I want to hit in a few weeks and that's really it for this year. I've got my sights set on 36" bias ply Irok's. Need to save up some cash first. It's on the list of things to get done before next season starts along with the doubler installed and Longs.

 

[Mbrantley]

Roger, I would really consider the 37" truxxis stickys...
I thought that the 36" Irock was an odd ball with shallow tread depth and round carcas

Matt

 

[rblank]

I'll look into it. I know another guy that ran the Maxxis (non-comp) and loved them. But in the end it's all about the money.

 

[Mbrantley]

Roger,

The Maxxis stuff is $$$ but very nice. I was actually talking about the Interco Truxxis molded w/ comp compound I am not sure what rim size they are avaliable in. Speaking of comp compound I wish they had the 42" Irok stickys when I bought mine

Matt

 

[rblank]

Running stickies when you're not in a comp is like cheating.

 

[crusier72]

OT. buy the biggest stickiest tires u can.

Let's see the pics of the BB sag pump. Then how about some flow analysis within the pump before and after you're flow mudifications to aleviate cavitation. It would appear you are on the right path by changing to a more robust designed pump.

 

[rblank]

Ok, last OT detour, I swear...

Creepy stickies only come in 40's, Trepedors come in 37's but I would need new rims. Even the standard Creepy's are $158 more each tire than the Irok. Too bad, at least I looked.

Back on track. I'd like to see some flow figures too. Good stuff there Mike. Maybe I need to read PoR and the Formula Toy forum more often.

 

[Mbrantley]

Mark,

I would like to do some redneck flow analysis on the next pump, maybe by using a 5gallon pal as a make shift res with a bulk head fitting for the suction line. I wonder at what point in the system would be the best to measure flow?

Roger,

Now is the right time to move up in wheel size from the 15" you will really benefit from the increased lateral stability and the prices for tires in the 17" and 18" have come down since the OEM's have started using them. So many choices

Matt

 

[rblank]

You're not helping....

 

[crusier72]

If I were to set up the test It would be just the pump in and out timed with two buckets. Set one as a res with 4ish Gal of fluid in it and another 5Gal pal to catch it all and do it with the pump on there now and again with the new pump in stock trim and post mod. If u want to get fancy rig up one of those electric motors u have @ about 850PRM pump speed with a jig on a bench and you could have a little more control without all the buggy getting in the way. Just a stop watch is sufficient and a appropriately graduated scale. Will the pump flow fluid with just (gravity*mass) pushing on it on the res side if so you might need a ball valve to make it more complicated yet accurate. Good luck.

More OT step up to 17" rims you will never want to go back.

 

[Mbrantley]

Mark,

having the two buckets was how I was envisioning the test however what would the data actually mean? as this would be done @ approx. zero psi, although I could use a valve and guage to alter the pressure. I wonder if the different pumps will have different flow vs psi curves or if they will just be offset by the difference in displacement.

This is starting to sound like fun....

Matt

 

[rblank]

This is the kind of stuff I like to see when I'm researching a new mod. I like to see REAL test data and WHY something worked or failed. Not the "My buddy has been running that for years and is the chit....."

If I didn't already have a set of 15x8 that I got for free I probably would, unless I sell them and my old tires and rims and get 17's.....hmmmmmm

 

[BigRedFJ40]

Matt,

I can grab our flowrater from work for a weekend. It will tell you gpm @whatever PSI. I use it all the time for setting up excavators with hammers, pulverizers and tampers. Neat toy but $$$$$$ (glad I didn't buy it)

 

[Mbrantley]

Hey Chris how have you been?

That flowrater sounds I would definitely like to take you up on the offer. what type of fittings would I need?

Matt

 

[Mbrantley]

I have made some progress on upgrading my steering pump in the past few weeks so I though I would update this thread. I bought a rebuilt "big bearing" sag pump from NAPA I am not sure of the exact application but I think that it was used on GM medium duty trucks. This pump uses a similar sized ring and rotor as my original hot rod pump but has a few major differences overall. First the pump body is longer allowing for more room inside for fluid flow, secondly the shaft rides on two bearings one is a roller and the other is a needle roller style allowing for increased durability and allows the rotor to float inside, the last major difference is the shaft uses a keyed pulley.

Since this pump is meant to be in a housing I had to do some modifications to run it with out the housing. In the pics you can see that I taped the pump body on top and the original inlets on the sides. I used 1/2 NPT on top and 1/8 NPT on the sides fed by a -6AN (3/8")hoses with a -12 AN fitting(3/4") supplying the three inlets. Allowing fluid flow from multiple ports seems to be the next logical step in keeping the pump full of fluid at all times.

Next I did some simple porting of the inlets and the outlet ( you can see some of this in the third pic along with machining the I.D. of the pump body and the O.D. of the rotor to allow more fluid flow on the suction side along with some shaping work on the ring side and O.D. I did not remove a large amount but considering the original dimensions it gave a large increase in volume. The work on the suction side is important because it seems to be a huge bottle neck.

The 5" pulley and hub are from PSC and are really nice, it seems there Superflo Comp pump uses the same pulley set up as I needed

In addition to the new pump I am going to make a small accumulator out of a old air shock body to add on the low pressure side of the system to keep 5 to 10 PSI charge on the system to help reduce cavitation further. I had tried to make a floating piston for my reservoir before but it was too far out of round so this will be attempt #2...

Matt