400 should be in the 500s. Great video Mark! It's good to see someone doing viper builds and breakdowns!

@marksslotcargarage

6 ай бұрын

Yeah, this one is not even hitting 400, definitely something off with the arm in that car.

MSCG..nice work, always enjoy your videos.

@marksslotcargarage

6 ай бұрын

Thanks!

I see you broke down and upgraded from the wife’s old cutting board. Great video.

@marksslotcargarage

6 ай бұрын

LOL, yeah, thanks Matt. I do still have the cutting board should I need it.

Check the gap in the arm .. run the tip of exacto knife in the gap make sure it’s clean.. then run a ball point pen between the plates and put a slight radius on them .. also make sure you have a shim on the front of arm and maybe take out end bell shim if you have one

@marksslotcargarage

6 ай бұрын

Thanks for the suggestions, on my cars I do run a .10 shim on the front of my arms, this arm did not have one. I did clean the commutator gaps, spacing of the arm that my buddy did was pretty good, I just think it is a low performing arm for what ever reason. All of my 3 ohm vipers are running much stronger than this 2.5 ohm arm. I will give it a few more tweaks and see if I can get more performance out of it.

Interesting. One thing I would say is just because an armature appears to be balanced doesn't necessarily mean whoever balanced it did a good job. But with that being said there seems to be a couple potential clues. The motor brushes that were in the chassis had some kind of obvious issue. The cause could be important. Additionally after you went through the chassis it ran a bit better but then slowed down. Makes me think it may have gotten too hot sometime in the past. Once it gets up to operating temperature there could be a short in the windings. Windings in any electrical device sometimes seem fine cold but once they warm up a short appears and sometimes even an open circuit. Doesn't seem bad enough for an open circuit though. I've seen cars that ran with only 2 of the 3 armature poles working. 1 of 3 windings open. At any rate I think you have the right idea that this arm isn't equal to yours.

@marksslotcargarage

6 ай бұрын

Thanks Jeff, and yeah I agree not knowing the history of it I don't think we will ever know. I did a little more work on it and added a shim to the from of the arm and changed the shim in the back and that helped a bit, got the Dyno up in the low 4's but then after running for a few minutes it drops back down to 3.7 which I agree is strange behavior and makes me question the health of the arm. I also tested the strength of the motor magnets against ones form my cars and they were the same so it is not the magnets.

I can’t say for sure but I suspect its the motor magnets. Personally I have gone down this road before. I would suggest pulling the arm and putting it in one of your fastest running poly mod cars and then test it. I have a bare chassis on hand for just this same reason

@marksslotcargarage

6 ай бұрын

Thanks for the suggestions. I thought about the motor magnets and took them out again and tested them, they were equal in strength to motor mags out of my cars so it's not the magnets. I am to the point where I feel it is the arm. Good idea swapping the arm into one of my cars, that would show for sure if it is the arm.

"Polymod" is one of those terms that has become a little nebulous and means different things to different people. Technically all it started out to mean is simply a car that's running compression molded polymer motor magnets. The term was coined back when they first hit the slot car market and weren't very common. Back then, they started the "CMPM" class. They were first made because they were much stronger than ceramics but more because they were "tunable" in manufacturing and could be made to any strength and, because they produced a more consistent and even field, they didn't need to be matched. The material any one batch of magnets is made out of is homogeneous so all the magnets produced are almost the same. Now, of course, they're everywhere and they're getting to be cheaper than ceramic magnets, especially the stronger matched ceramics which are now increasing in demand in order to meet class rule restrictions.

@marksslotcargarage

6 ай бұрын

Yup, thanks Ralph I was aware of all that. Viper does sell a car they label as a PolyMod which is what this car was supposed to be but I have my doubts that the arm in my friends car is the 2.5 ohm wide gap high heat arm Viper says is in their PolyMod car. Also all of my 3 ohm Viper modified run in the 4.5 range on my Dyno while this car does not even hit 4, seems to me the arm is just not where it should be. I mainly did this vid as a favor to my friend who was curious about the arm in the chassis.

@BigRalphSmith

6 ай бұрын

@@marksslotcargarage Did I drone on? 🙄The poorly defined terms cause me some headaches so sorry about that.

@BigRalphSmith

6 ай бұрын

@@marksslotcargarage Got a Gauss meter? I'm thinkin those magnets just aren't as strong as yours.

@marksslotcargarage

6 ай бұрын

I was thinking that as well about the motor magnets, I do have a meter and can check them....thx.

I agree with the comments regarding the arm. Judging from the com and the laminations the arm doesn't look like a quality piece of work. You talked about armature spacing and play but is the motor centered in the magnetic field? If it being shoved forward or backwards then performance will suffer. In addition the endbell needs to be tweaked and fully broken in before that thing will sing. Finally as someone else commented Polymod means different things to different people. Swapping Level 10 magnets and a 2.5 ohm motor into an otherwise stock chassis doesn't make a stock Viper into a Polymod.

@marksslotcargarage

6 ай бұрын

Thanks, all good points. I would say yes the motor is spaced properly in the center of the magnets, the endbell is tweaked and broken in, I also just did a follow up video that I am about to post where I took the arm and put it in one of my 3 ohm Viper modified chassis and the issue with the slower than expected Dyno numbers followed that arm. When I say PolyMod, I mean what Viper sells as a PolyMod on their site, they have a specific spec car they call a PolyMod which this car was supposed to be. I have build several 2.5 ohm Vipers, they all hit above 500 on the Dyno easily without any major tweaking so I agree this arm just does not seem to be good quality.

Is that a tunable end bell, if it is I would try turning it away from center to see if you get more rpm

@marksslotcargarage

6 ай бұрын

Yea and already had it set to advanced timing, it did not help. Thx.

those chassis mags may not be what they are supposed to be, take them out and try it again, swap them with one of your chassis`. 👍🏁

@marksslotcargarage

6 ай бұрын

Yeah Rich, yeah I was thinking about the motor magnets as well, that would be a good test.

@slotvalleyracing

6 ай бұрын

Hey Brother, been missing you. Are you ever going to rejoin us?

@marksslotcargarage

6 ай бұрын

I tested the magnets against ones from my cars, they were the same so it is not the magnets.

@DTIMainline

6 ай бұрын

ok, cool, must just be a lame armature. great video, tnx Mark.@@marksslotcargarage

You could swap your friends 23 tooth crown gear with your 22 tooth to get more r p ms but that arm sounds tired.

@marksslotcargarage

6 ай бұрын

I did swap the crown gear in the video, it helped a little but agree the arm is not where it should be. Thx.